IDL Help for Goddard Utilities

 NAME:
     AD2XY
 PURPOSE:
     Compute X and Y from native coordinates and a FITS  astrometry structure
 EXPLANATION:
     If a WCS projection (Calabretta & Greisen 2002, A&A, 395, 1077) is 
     present, then the procedure WCSXY2SPH is used to compute native 
     coordinates.   If distortion is present then this is corrected.  
     In all cases, the inverse of the CD matrix is applied and offset 
     from the reference pixel to obtain X and Y. 

     AD2XY is generally meant to be used internal to other procedures.   For 
     interactive purposes, use ADXY.

 CALLING SEQUENCE:
     AD2XY, a ,d, astr, x, y   

 INPUTS:
     A -     R.A. or longitude in DEGREES, scalar or vector
     D -     Dec. or longitude in DEGREES, scalar or vector
     ASTR - astrometry structure, output from EXTAST procedure containing:
        .CD   -  2 x 2 array containing the astrometry parameters CD1_1 CD1_2
               in DEGREES/PIXEL                                   CD2_1 CD2_2
        .CDELT - 2 element vector giving increment at reference point in
               DEGREES/PIXEL
        .CRPIX - 2 element vector giving X and Y coordinates of reference pixel
               (def = NAXIS/2) in FITS convention (first pixel is 1,1)
        .CRVAL - 2 element vector giving coordinates of the reference pixel 
               in DEGREES
        .CTYPE - 2 element vector giving projection types 
        .LONGPOLE - scalar longitude of north pole (default = 180) 
        .PV2 - Vector of additional parameter (e.g. PV2_1, PV2_2) needed in 
               some projections
        .DISTORT - Optional substructure specifying distortion parameters

 OUTPUTS:
     X     - row position in pixels, scalar or vector
     Y     - column position in pixels, scalar or vector

     X,Y will be in the standard IDL convention (first pixel is 0), and
     *not* the FITS convention (first pixel is 1)
 NOTES:
      AD2XY tests for presence of WCS coordinates by the presence of a dash 
      in the 5th character position in the value of CTYPE (e.g 'DEC--SIN').
 PROCEDURES USED:
       TAG_EXIST(), WCSSPH2XY
 REVISION HISTORY:
     Converted to IDL by B. Boothman, SASC Tech, 4/21/86
     Use astrometry structure,  W. Landsman      Jan. 1994   
     Do computation correctly in degrees  W. Landsman       Dec. 1994
     Only pass 2 CRVAL values to WCSSPH2XY   W. Landsman      June 1995
     Don't subscript CTYPE      W. Landsman       August 1995        
     Understand reversed X,Y (X-Dec, Y-RA) axes,   W. Landsman  October 1998
     Consistent conversion between CROTA and CD matrix W. Landsman October 2000
     No special case for tangent projection W. Landsman June 2003
     Work for non-WCS coordinate transformations W. Landsman Oct 2004
     Use CRVAL reference point for non-WCS transformation  W.L. March 2007
     Use post V6.0 notation  W.L. July 2009

(See $IDLUTILS_DIR/goddard/pro/astrom/ad2xy.pro)

ADSTRING

 NAME:
       ADSTRING
 PURPOSE:
       Return RA and Dec as character string(s) in sexigesimal format.
 EXPLANATION:
       RA and Dec may be entered as either a 2 element vector or as
       two separate vectors (or scalars).  One can also specify the precision 
       of the declination in digits after the decimal point.

 CALLING SEQUENCE
       result = ADSTRING( ra_dec, precision, /TRUNCATE )           
               or
       result = ADSTRING( ra,dec,[ precision, /TRUNCATE ] )
               or
       result = ADSTRING( dec, [ PRECISION= ] 

 INPUTS:
       RA_DEC - 2 element vector giving the Right Ascension and declination
               in decimal degrees.
                     or
       RA     - Right ascension in decimal degrees, numeric scalar or vector
       DEC    - Declination in decimal degrees, numeric scalar or vector

 OPTIONAL INPUT:
       PRECISION  - Integer scalar (0-4) giving the number of digits after the 
               decimal of DEClination.   The RA is automatically 1 digit more.
               This parameter may either be the third parameter after RA,DEC 
               or the second parameter after [RA,DEC].  If only DEC is supplied 
               then precision must be supplied as a keyword parameter.   If no
               PRECISION parameter or keyword is passed, a  precision of 1 for
               both RA and DEC is returned to maintain  compatibility with past
               ADSTRING versions.    Values of  precision larger than 4 will 
               be truncated to 4.    If PRECISION is 3 or 4, then RA and Dec 
               should be input as double precision.
 OPTIONAL INPUT KEYWORD:
       /TRUNCATE - if set, then the last displayed digit in the output is 
               truncated in precision rather than rounded.   This option is
               useful if ADSTRING() is used to form an official IAU name 
               (see http://vizier.u-strasbg.fr/Dic/iau-spec.htx) with 
               coordinate specification.   The IAU name will typically be
               be created by applying STRCOMPRESS/REMOVE) after the ADSTRING()
               call, e.g. 
              strcompress( adstring(ra,dec,0,/truncate), /remove)   ;IAU format
        PRECISION = Alternate method of supplying the precision parameter, 
 OUTPUT:
       RESULT - Character string(s) containing HR,MIN,SEC,DEC,MIN,SEC formatted
               as ( 2I3,F5.(p+1),2I3,F4.p ) where p is the PRECISION 
               parameter.    If only a single scalar is supplied it is 
               converted to a sexigesimal string (2I3,F5.1).

 EXAMPLE:
       (1) Display CRVAL coordinates in a FITS header, H

       IDL> crval = sxpar(h,'CRVAL*')  ;Extract 2 element CRVAL vector (degs)
       IDL> print, adstring(crval)     ;Print CRVAL vector sexigesimal format

       (2)  print,adstring(30.42,-1.23,1)  ==>  ' 02 01 40.80  -01 13 48.0'
            print,adstring(30.42,+0.23)    ==>  ' 02 01 40.8   +00 13 48.0'    
            print,adstring(+0.23)          ==>  '+00 13 48.0'

       (3) The first two calls in (2) can be combined in a single call using
           vector input
              print,adstring([30.42,30.42],[-1.23,0.23], 1)
 PROCEDURES CALLED:
       RADEC, SIXTY()

 REVISION HISTORY:
       Written   W. Landsman                      June 1988
       Addition of variable precision and DEC seconds precision fix. 
       ver.  Aug. 1990 [E. Deutsch]
       Output formatting spiffed up       October 1991 [W. Landsman]
       Remove ZPARCHECK call, accept 1 element vector  April 1992 [W. Landsman]
       Call ROUND() instead of NINT()    February 1996  [W. Landsman]
       Check roundoff past 60s           October 1997   [W. Landsman]
       Work for Precision =4             November 1997  [W. Landsman]
       Major rewrite to allow vector inputs   W. Landsman  February 2000
       Fix possible error in seconds display when Precision=0 
                               P. Broos/W. Landsman April 2002
       Added /TRUNCATE keyword, put leading zeros in seconds display
                               P. Broos/W. Landsman September 2002
       Fix declination zero values under vector processing W.Landsman Feb 2004
       Fix possible problem in leading zero display W. Landsman June 2004
       Assume since V5.4, omit fstring() call  W. Landsman April 2006
       Fix significant bug when round a declination with -1<dec<0 
          Add PRECISION keyword    W.L. Aug 2008
       Use formatting for "+" and "0"  W. L.    May 2009

(See $IDLUTILS_DIR/goddard/pro/astro/adstring.pro)

ADXY

 NAME:
       ADXY
 PURPOSE:
       Use a FITS header to convert astronomical to pixel coordinates
 EXPLANATION:
       Use an image header to compute X and Y positions, given the
       RA and Dec (or longitude, latitude) in decimal degrees.  

 CALLING SEQUENCE:
       ADXY, HDR               ;Prompt for Ra and DEC 
       ADXY, hdr, a, d, x, y, [ /PRINT, ALT= ]

 INPUTS:
       HDR - FITS Image header containing astrometry parameters

 OPTIONAL INPUTS:
       A - Right ascension in decimal DEGREES, scalar or vector
       D - Declination in decimal DEGREES, scalar or vector        

       If A and D are not supplied, user will be prompted to supply
       them in either decimal degrees or HR,MIN,SEC,DEG,MN,SC format.

 OPTIONAL OUTPUT:
       X     - row position in pixels, same number of elements as A and D
       Y     - column position in pixels

       X and Y will be in standard IDL convention (first pixel is 0) and not
       the FITS convention (first pixel is 1).      As in FITS an integral
       value corresponds to the center of a pixel.
 OPTIONAL KEYWORD INPUT:
       /PRINT - If this keyword is set and non-zero, then results are displayed
               at the terminal.
       ALT -  single character 'A' through 'Z' or ' ' specifying an alternate 
             astrometry system present in the FITS header.    The default is
             to use the primary astrometry or ALT = ' '.   If /ALT is set, 
             then this is equivalent to ALT = 'A'.   See Section 3.3 of 
             Greisen & Calabretta (2002, A&A, 395, 1061) for information about
             alternate astrometry keywords.

 OPERATIONAL NOTES:
       If less than 5 parameters are supplied, or if the /PRINT keyword is
       set, then the X and Y positions are displayed at the terminal.

       If the procedure is to be used repeatedly with the same header,
       then it would be faster to use AD2XY.

 PROCEDURES CALLED:
       AD2XY, ADSTRING(), EXTAST, GETOPT(), TEN()

 REVISION HISTORY:
       W. Landsman                 HSTX          January, 1988
       Use astrometry structure   W. Landsman   January, 1994  
       Changed default ADSTRING format   W. Landsman    September, 1995
       Check if latitude/longitude reversed in CTYPE keyword W. L. Feb. 2004
       Added ALT keyword   W. Landsman   September 2004
       Work for non-spherical coordinate transformation W. Landsman May 2005 
       More informative error message if astrometry missing W.L. Feb 2008
       Cosmetic updates W.L. July 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/adxy.pro)

AIRTOVAC

 NAME:
       AIRTOVAC
 PURPOSE:
       Convert air wavelengths to vacuum wavelengths 
 EXPLANATION:
       Wavelengths are corrected for the index of refraction of air under 
       standard conditions.  Wavelength values below 2000 A will not be 
       altered.  Uses relation of Ciddor (1996).

 CALLING SEQUENCE:
       AIRTOVAC, WAVE_AIR, [ WAVE_VAC]

 INPUT/OUTPUT:
       WAVE_AIR - Wavelength in Angstroms, scalar or vector
               If this is the only parameter supplied, it will be updated on
               output to contain double precision vacuum wavelength(s). 
 OPTIONAL OUTPUT:
        WAVE_VAC - Vacuum wavelength in Angstroms, same number of elements as
                 WAVE_AIR, double precision

 EXAMPLE:
       If the air wavelength is  W = 6056.125 (a Krypton line), then 
       AIRTOVAC, W yields an vacuum wavelength of W = 6057.8019

 METHOD:
	Formula from Ciddor 1996, Applied Optics 62, 958

 NOTES: 
       Take care within 1 A of 2000 A.   Wavelengths below 2000 A *in air* are
       not altered.       
 REVISION HISTORY
       Written W. Landsman                November 1991
       Use Ciddor (1996) formula for better accuracy in the infrared 
           Added optional output vector, W Landsman Mar 2011
       Iterate for better precision W.L./D. Schlegel  Mar 2011

(See $IDLUTILS_DIR/goddard/pro/astro/airtovac.pro)

AITOFF

 NAME:
       AITOFF
 PURPOSE:
       Convert longitude, latitude to X,Y using an AITOFF projection.
 EXPLANATION:
       This procedure can be used to create an all-sky map in Galactic 
       coordinates with an equal-area Aitoff projection.  Output map 
       coordinates are zero longitude centered.

 CALLING SEQUENCE:
       AITOFF, L, B, X, Y 

 INPUTS:
       L - longitude - scalar or vector, in degrees
       B - latitude - same number of elements as L, in degrees

 OUTPUTS:
       X - X coordinate, same number of elements as L.   X is normalized to
               be between -180 and 180
       Y - Y coordinate, same number of elements as L.  Y is normalized to
               be between -90 and 90.

 NOTES:
       See AIPS memo No. 46, page 4, for details of the algorithm.  This
       version of AITOFF assumes the projection is centered at b=0 degrees.

 REVISION HISTORY:
       Written  W.B. Landsman  STX          December 1989
       Modified for Unix:
               J. Bloch        LANL SST-9      5/16/91 1.1
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/aitoff.pro)

AITOFF_GRID

 NAME:
       AITOFF_GRID

 PURPOSE:
       Produce an overlay of latitude and longitude lines over a plot or image
 EXPLANATION:
       The grid is plotted on the current graphics device. AITOFF_GRID 
       assumes that the ouput plot coordinates span the x-range of 
       -180 to 180 and the y-range goes from -90 to 90.

 CALLING SEQUENCE:

       AITOFF_GRID [,DLONG,DLAT, LABEL=, /NEW, CHARTHICK=, CHARSIZE=, 
                     FONT=, _EXTRA=]

 OPTIONAL INPUTS:

       DLONG   = Optional input longitude line spacing in degrees. If left
                 out, defaults to 30.
       DLAT    = Optional input latitude line spacing in degrees. If left
                 out, defaults to 30.

 OPTIONAL INPUT KEYWORDS:

       LABEL           = Optional keyword specifying that the latitude and
                         longitude lines on the prime meridian and the
                         equator should be labeled in degrees. If LABELS is
                         given a value of 2, i.e. LABELS=2, then the longitude
                         labels will be in hours instead of degrees.
        CHARSIZE       = If /LABEL is set, then CHARSIZE specifies the size
                         of the label characters (passed to XYOUTS)
        CHARTHICK     =  If /LABEL is set, then CHARTHICK specifies the 
                         thickness of the label characters (passed to XYOUTS)
       FONT          =   scalar font graphics keyword (-1,0 or 1) for text
       /NEW          =   If this keyword is set, then AITOFF_GRID will create
                         a new plot grid, rather than overlay an existing plot.

       Any valid keyword to OPLOT such as COLOR, LINESTYLE, THICK can be 
       passed to AITOFF_GRID (though the _EXTRA facility) to to specify the
       color, style, or thickness of the grid lines.
 OUTPUTS:
       Draws grid lines on current graphics device.

 EXAMPLE:
       Create a labeled Aitoff grid of the Galaxy, and overlay stars at 
       specified Galactic longitudes, glong and latitudes, glat

       IDL> aitoff_grid,/label,/new        ;Create labeled grid
       IDL> aitoff, glong, glat, x,y      ;Convert to X,Y coordinates
       IDL> plots,x,y,psym=2              ;Overlay "star" positions

 PROCEDURES USED:
       AITOFF
 NOTES:
       If labeling in hours (LABEL=2) then the longitude spacing should be
       a multiple of 15 degrees

 AUTHOR AND MODIFICATIONS:

       J. Bloch        1.2     6/2/91
       Converted to IDL V5.0   W. Landsman   September 1997
       Create default plotting coords, if needed   W. Landsman  August 2000
       Added _EXTRA, CHARTHICK, CHARSIZE keywords  W. Landsman  March 2001
       Several tweaks, plot only hours not minutes W. Landsman January 2002
       Allow FONT keyword to be passed to XYOUTS.  T. Robishaw Apr. 2006

(See $IDLUTILS_DIR/goddard/pro/astro/aitoff_grid.pro)

ALTAZ2HADEC

  NAME:
    ALTAZ2HADEC
 PURPOSE:
    Convert Horizon (Alt-Az) coordinates to Hour Angle and Declination.
 EXPLANATION::
    Can deal with the NCP singularity.    Intended mainly to be used by
    program hor2eq.pro
 CALLING SEQUENCE:
   ALTAZ2HADEC, alt, az, lat, ha, dec

 INPUTS
   alt - the local apparent altitude, in DEGREES, scalar or vector
   az  - the local apparent azimuth, in DEGREES, scalar or vector,
         measured EAST of NORTH!!!  If you have measured azimuth west-of-south
        (like the book MEEUS does), convert it to east of north via:
                       az = (az + 180) mod 360

   lat -  the local geodetic latitude, in DEGREES, scalar or vector.

 OUTPUTS
   ha  -  the local apparent hour angle, in DEGREES.  The hour angle is the 
          time that right ascension of 0 hours crosses the local meridian.  
          It is unambiguously defined.
   dec -  the local apparent declination, in DEGREES.

 EXAMPLE:
     Arcturus is observed at an apparent altitude of 59d,05m,10s and an 
     azimuth (measured east of north) of 133d,18m,29s while at the 
     latitude of +43.07833 degrees.
     What are the local hour angle and declination of this object?

     IDL> altaz2hadec, ten(59,05,10), ten(133,18,29), 43.07833, ha, dec
     ===> Hour angle ha = 336.683 degrees
          Declination, dec = 19.1824 degrees

       The widely available XEPHEM code gets:
                 Hour Angle = 336.683
                 Declination = 19.1824

 REVISION HISTORY:
    Written  Chris O'Dell Univ. of Wisconsin-Madison May 2002

(See $IDLUTILS_DIR/goddard/pro/astro/altaz2hadec.pro)

AL_LEGEND

 NAME:
       AL_LEGEND
 PURPOSE:
       Create an annotation legend for a plot.
 EXPLANATION:
       This procedure was originally named LEGEND, but a distinct LEGEND() 
       function was introduced into IDL V8.0.   Therefore, the      
       original LEGEND procedure in the Astronomy Library is renamed to
       AL_LEGEND.    
           
       This procedure makes a legend for a plot.  The legend can contain
       a mixture of symbols, linestyles, Hershey characters (vectorfont),
       and filled polygons (usersym).  A test procedure, legendtest.pro,
       shows legend's capabilities.  Placement of the legend is controlled
       with keywords like /right, /top, and /center or by using a position
       keyword for exact placement (position=[x,y]) or via mouse (/position).
 CALLING SEQUENCE:
       AL_LEGEND [,items][,keyword options]
 EXAMPLES:
       The call:
               al_legend,['Plus sign','Asterisk','Period'],psym=[1,2,3]
         produces:
               -----------------
               |               |
               |  + Plus sign  |
               |  * Asterisk   |
               |  . Period     |
               |               |
               -----------------
         Each symbol is drawn with a cgPlots command, so they look OK.
         Other examples are given in optional output keywords.

       lines = indgen(6)                       ; for line styles
       items = 'linestyle '+strtrim(lines,2)   ; annotations
       al_legend,items,linestyle=lines         ; vertical legend---upper left
       items = ['Plus sign','Asterisk','Period']
       sym = [1,2,3]
       al_legend,items,psym=sym                   ; ditto except using symbols
       al_legend,items,psym=sym,/horizontal       ; horizontal format
       al_legend,items,psym=sym,box=0             ; sans border
       al_legend,items,psym=sym,delimiter='='     ; embed '=' betw psym & text
       al_legend,items,psym=sym,margin=2          ; 2-character margin
       al_legend,items,psym=sym,position=[x,y]    ; upper left in data coords
       al_legend,items,psym=sym,pos=[x,y],/norm   ; upper left in normal coords
       al_legend,items,psym=sym,pos=[x,y],/device ; upper left in device coords
       al_legend,items,psym=sym,/position         ; interactive position
       al_legend,items,psym=sym,/right            ; at upper right
       al_legend,items,psym=sym,/bottom           ; at lower left
       al_legenditems,psym=sym,/center           ; approximately near center
       al_legend,items,psym=sym,number=2          ; plot two symbols, not one
     Plot 3 filled colored squares
       al_legend,items,/fill,psym=[8,8,8],colors=['red','green','blue']

        Another example of the use of AL_LEGEND can be found at 
        http://www.idlcoyote.com/cg_tips/al_legend.php
 INPUTS:
       items = text for the items in the legend, a string array.
               For example, items = ['diamond','asterisk','square'].
               You can omit items if you don't want any text labels.
 OPTIONAL INPUT KEYWORDS:

       linestyle = array of linestyle numbers  If linestyle[i] < 0, then omit
               ith symbol or line to allow a multi-line entry.     If 
               linestyle = -99 then text will be left-justified.  
       psym = array of plot symbol numbers.  If psym[i] is negative, then a
               line connects pts for ith item.  If psym[i] = 8, then the
               procedure usersym is called with vertices define in the
               keyword usersym.   If psym[i] = 88, then use the previously
               defined user symbol.    If 11 <= psym[i] <= 46 then David
               Fanning's function SYMCAT() will be used for additional symbols.
               (http://www.idlcoyote.com/programs/symcat.pro).   Note that
               PSYM=10 (histogram plot mode) is not allowed since it 
               cannot be used with the cgPlots command.
       vectorfont = vector-drawn characters for the sym/line column, e.g.,
               ['!9B!3','!9C!3','!9D!3'] produces an open square, a checkmark,
               and a partial derivative, which might have accompanying items
               ['BOX','CHECK','PARTIAL DERIVATIVE'].
               There is no check that !p.font is set properly, e.g., -1 for
               X and 0 for PostScript.  This can produce an error, e.g., use
               !20 with PostScript and !p.font=0, but allows use of Hershey
               *AND* PostScript fonts together.
       N. B.: Choose any of linestyle, psym, and/or vectorfont.  If none is
               present, only the text is output.  If more than one
               is present, all need the same number of elements, and normal
               plot behaviour occurs.
               By default, if psym is positive, you get one point so there is
               no connecting line.  If vectorfont[i] = '',
               then cgPlots is called to make a symbol or a line, but if
               vectorfont[i] is a non-null string, then cgText is called.
       /help = flag to print header
       /horizontal = flag to make the legend horizontal
       /vertical = flag to make the legend vertical (D=vertical)
       background_color - color name or number to fill the legend box.
              Automatically sets /clear.    (D = -1)
       box = flag to include/omit box around the legend (D=include)
		  outline_color = color of box outline (D = !P.color)
       bthick = thickness of the legend box (D = !P.thick)
       charsize = just like !p.charsize for plot labels
       charthick = just like !p.charthick for plot labels
       clear = flag to clear the box area before drawing the legend
       colors = array of colors names or numbers for plot symbols/lines 
          See cgCOLOR for list of color names.   Default is 'Opposite'
          If you are using index colors (0-255), then supply color as a byte,
          integer or string, but not as a long, which will be interpreted as 
          a decomposed color. See http://www.idlcoyote.com/cg_tips/legcolor.php
       delimiter = embedded character(s) between symbol and text (D=none)
       font = scalar font graphics keyword (-1,0 or 1) for text
       linsize = Scale factor for line length (0-1), default = 1
                 Set to 0 to give a dot, 0.5 give half default line length   
       margin = margin around text measured in characters and lines
       number = number of plot symbols to plot or length of line (D=1)
       spacing = line spacing (D=bit more than character height)
       position = data coordinates of the /top (D) /left (D) of the legend
       pspacing = psym spacing (D=3 characters) (when number of symbols is
             greater than 1)
       textcolors = array of color names or numbers for text.  See cgCOLOR
          for a list of color names.   Default is 'Opposite' of background
       thick = array of line thickness numbers (D = !P.thick), if used, then 
               linestyle must also be specified
       normal = use normal coordinates for position, not data
       device = use device coordinates for position, not data
       /window - if set then send legend to a resizeable graphics window
       usersym = 2-D array of vertices, cf. usersym in IDL manual. 
             (/USERSYM =square, default is to use existing USERSYM definition)
       /fill = flag to fill the usersym
       /left_legend = flag to place legend snug against left side of plot
                 window (D)
       /right_legend = flag to place legend snug against right side of plot
               window.    If /right,pos=[x,y], then x is position of RHS and
               text runs right-to-left.
       /top_legend = flag to place legend snug against top of plot window (D)
       /bottom = flag to place legend snug against bottom of plot window
               /top,pos=[x,y] and /bottom,pos=[x,y] produce same positions.

       If LINESTYLE, PSYM, VECTORFONT, SYMSIZE, THICK, COLORS, or 
       TEXTCOLORS are supplied as scalars, then the scalar value is set for 
       every line or symbol in the legend.
 Outputs:
       legend to current plot device
 OPTIONAL OUTPUT KEYWORDS:
       corners = 4-element array, like !p.position, of the normalized
         coords for the box (even if box=0): [llx,lly,urx,ury].
         Useful for multi-column or multi-line legends, for example,
         to make a 2-column legend, you might do the following:
           c1_items = ['diamond','asterisk','square']
           c1_psym = [4,2,6]
           c2_items = ['solid','dashed','dotted']
           c2_line = [0,2,1]
           al_legend,c1_items,psym=c1_psym,corners=c1,box=0
           al_legend,c2_items,line=c2_line,corners=c2,box=0,pos=[c1[2],c1[3]]
           c = [c1[0]<c2[0],c1[1]<c2[1],c1[2]>c2[2],c1[3]>c2[3]]
         cgplots,[c[0],c[0],c[2],c[2],c[0]],[c[1],c[3],c[3],c[1],c[1]],/norm

         Useful also to place the legend.  Here's an automatic way to place
         the legend in the lower right corner.  The difficulty is that the
         legend's width is unknown until it is plotted.  In this example,
         the legend is plotted twice: the first time in the upper left, the
         second time in the lower right.

         al_legend,['1','22','333','4444'],linestyle=indgen(4),corners=corners
                       ; BOGUS LEGEND---FIRST TIME TO REPORT CORNERS
           xydims = [corners[2]-corners[0],corners[3]-corners[1]]
                       ; SAVE WIDTH AND HEIGHT
           chdim=[!d.x_ch_size/float(!d.x_size),!d.y_ch_size/float(!d.y_size)]
                       ; DIMENSIONS OF ONE CHARACTER IN NORMALIZED COORDS
           pos = [!x.window[1]-chdim[0]-xydims[0] $
                       ,!y.window[0]+chdim[1]+xydims[1]]
                       ; CALCULATE POSITION FOR LOWER RIGHT
           cgplot,findgen(10)    ; SIMPLE PLOT; YOU DO WHATEVER YOU WANT HERE.
           al_legend,['1','22','333','4444'],linestyle=indgen(4),pos=pos
                       ; REDO THE LEGEND IN LOWER RIGHT CORNER
         You can modify the pos calculation to place the legend where you
         want.  For example to place it in the upper right:
           pos = [!x.window[1]-chdim[0]-xydims[0],!y.window[1]-xydims[1]]
 Common blocks:
       none
 Procedure:
       If keyword help is set, call doc_library to print header.
       See notes in the code.  Much of the code deals with placement of the
       legend.  The main problem with placement is not being
       able to sense the length of a string before it is output.  Some crude
       approximations are used for centering.
 Restrictions:
       Here are some things that aren't implemented.
       - An orientation keyword would allow lines at angles in the legend.
       - An array of usersyms would be nice---simple change.
       - An order option to interchange symbols and text might be nice.
       - Somebody might like double boxes, e.g., with box = 2.
       - Another feature might be a continuous bar with ticks and text.
       - There are no guards to avoid writing outside the plot area.
       - There is no provision for multi-line text, e.g., '1st line!c2nd line'
         Sensing !c would be easy, but !c isn't implemented for PostScript.
         A better way might be to simply output the 2nd line as another item
         but without any accompanying symbol or linestyle.  A flag to omit
         the symbol and linestyle is linestyle[i] = -1.
       - There is no ability to make a title line containing any of titles
         for the legend, for the symbols, or for the text.
 Side Effects:
 Modification history:
       write, 24-25 Aug 92, F K Knight (knight@ll.mit.edu)
       allow omission of items or omission of both psym and linestyle, add
         corners keyword to facilitate multi-column legends, improve place-
         ment of symbols and text, add guards for unequal size, 26 Aug 92, FKK
       add linestyle(i)=-1 to suppress a single symbol/line, 27 Aug 92, FKK
       add keyword vectorfont to allow characters in the sym/line column,
         28 Aug 92, FKK
       add /top, /bottom, /left, /right keywords for automatic placement at
         the four corners of the plot window.  The /right keyword forces
         right-to-left printing of menu. 18 Jun 93, FKK
       change default position to data coords and add normal, data, and
         device keywords, 17 Jan 94, FKK
       add /center keyword for positioning, but it is not precise because
         text string lengths cannot be known in advance, 17 Jan 94, FKK
       add interactive positioning with /position keyword, 17 Jan 94, FKK
       allow a legend with just text, no plotting symbols.  This helps in
         simply describing a plot or writing assumptions done, 4 Feb 94, FKK
       added thick, symsize, and clear keyword Feb 96, W. Landsman HSTX
               David Seed, HR Wallingford, d.seed@hrwallingford.co.uk
       allow scalar specification of keywords, Mar 96, W. Landsman HSTX
       added charthick keyword, June 96, W. Landsman HSTX
       Made keyword names  left,right,top,bottom,center longer,
                                 Aug 16, 2000, Kim Tolbert
       Added ability to have regular text lines in addition to plot legend 
       lines in legend.  If linestyle is -99 that item is left-justified.
       Previously, only option for no sym/line was linestyle=-1, but then text
       was lined up after sym/line column.    10 Oct 2000, Kim Tolbert
       Make default value of thick = !P.thick  W. Landsman  Jan. 2001
       Don't overwrite existing USERSYM definition  W. Landsman Mar. 2002
	     Added outline_color BT 24 MAY 2004
       Pass font keyword to cgText commands.  M. Fitzgerald, Sep. 2005
       Default spacing, pspacing should be relative to charsize. M. Perrin, July 2007
       Don't modify position keyword  A. Kimball/ W. Landsman Jul 2007
       Small update to Jul 2007 for /NORMAL coords.  W. Landsman Aug 2007
       Use SYMCAT() plotting symbols for 11<=PSYM<=46   W. Landsman  Nov 2009
       Make a sharper box edge T. Robishaw/W.Landsman July 2010
       Added BTHICK keyword W. Landsman October 2010
       Added BACKGROUND_COLOR keyword  W. Landsman February 2011
       Incorporate Coyote graphics  W. Landsman  February 2011
       Added LINSIZE keyword W.L./V.Gonzalez   May 2011
       Fixed a small problem with Convert_Coord when the Window keyword is set. 
                         David Fanning, May 2011.
       Fixed problem when /clear and /Window are set J. Bailin/WL   May 2011
       CGQUERY was called instead of CGCONTROL   W.L.  June 2011
       Fixed typo preventing BTHICK keyword from working W.L. Dec 2011
       Remove call to SYMCAT() W.L. Dec 2011
       Changed the way the WINDOW keyword adds commands to cgWindow, and
       now default to BACKGROUND for background color. 1 Feb 2012 David Fanning
       Allow 1 element SYMSIZE for vector input, WL Apr 2012.

(See $IDLUTILS_DIR/goddard/pro/plot/al_legend.pro)

APER

 NAME:
      APER
 PURPOSE:
      Compute concentric aperture photometry (adapted from DAOPHOT) 
 EXPLANATION:
     APER can compute photometry in several user-specified aperture radii.  
     A separate sky value is computed for each source using specified inner 
     and outer sky radii.   

 CALLING SEQUENCE:
     APER, image, xc, yc, [ mags, errap, sky, skyerr, phpadu, apr, skyrad, 
                       badpix, /NAN, /EXACT, /FLUX, PRINT = , /SILENT, 
                       /MEANBACK, MINSKY=, SETSKYVAL = ]
 INPUTS:
     IMAGE -  input image array
     XC     - vector of x coordinates. 
     YC     - vector of y coordinates

 OPTIONAL INPUTS:
     PHPADU - Photons per Analog Digital Units, numeric scalar.  Converts
               the data numbers in IMAGE to photon units.  (APER assumes
               Poisson statistics.)  
     APR    - Vector of up to 12 REAL photometry aperture radii.
     SKYRAD - Two element vector giving the inner and outer radii
               to be used for the sky annulus.   Ignored if the SETSKYVAL
              keyword is set.
     BADPIX - Two element vector giving the minimum and maximum value
               of a good pixel.   If badpix is not supplied or if BADPIX[0] is
               equal to BADPIX[1] then it is assumed that there are no bad
               pixels.     Note that fluxes will not be computed for any star
               with a bad pixel within the aperture area, but that bad pixels
               will be simply ignored for the sky computation.    The BADPIX
               parameter is ignored if the /NAN keyword is set.

 OPTIONAL KEYWORD INPUTS:
     CLIPSIG - if /MEANBACK is set, then this is the number of sigma at which 
             to clip the background.  Default=3
     CONVERGE_NUM:  if /MEANBACK is set then if the proportion of 
           rejected pixels is less than this fraction, the iterations stop.  
           Default=0.02, i.e., iteration stops if fewer than 2% of pixels 
           excluded.
     /EXACT -  By default, APER counts subpixels, but uses a polygon 
             approximation for the intersection of a circular aperture with
             a square pixel (and normalizes the total area of the sum of the
             pixels to exactly match the circular area).   If the /EXACT 
             keyword, then the intersection of the circular aperture with a
             square pixel is computed exactly.    The /EXACT keyword is much
             slower and is only needed when small (~2 pixels) apertures are
             used with very undersampled data.    
     /FLUX - By default, APER uses a magnitude system where a magnitude of
               25 corresponds to 1 flux unit.   If set, then APER will keep
              results in flux units instead of magnitudes.    
     MAXITER if /MEANBACK is set then this is the ceiling on number of 
             clipping iterations of the background.  Default=5
     /MEANBACK - if set, then the background is computed using the 3 sigma 
             clipped mean (using meanclip.pro) rather than using the mode 
             computed with mmm.pro.    This keyword is useful for the Poisson 
             count regime or where contamination is known  to be minimal.
      MINSKY - Integer giving mininum number of sky values to be used with MMM
             APER will not compute a flux if fewer valid sky elements are 
               within the sky annulus.   Default = 20.
     /NAN  - If set then APER will check for NAN values in the image.   /NAN
             takes precedence over the BADPIX parameter.   Note that fluxes 
             will not be computed for any star with a NAN pixel within the 
             aperture area, but that NAN pixels will be simply ignored for 
             the sky computation.
     PRINT - if set and non-zero then APER will also write its results to
               a file aper.prt.   One can specify the output file name by
               setting PRINT = 'filename'.
     READNOISE - Scalar giving the read noise (or minimum noise for any
              pixel.   This value is passed to the procedure mmm.pro when
              computing the sky, and is only need for images where
              the noise is low, and pixel values are quantized.   
     /SILENT -  If supplied and non-zero then no output is displayed to the
               terminal.
     SETSKYVAL - Use this keyword to force the sky to a specified value 
               rather than have APER compute a sky value.    SETSKYVAL 
               can either be a scalar specifying the sky value to use for 
               all sources, or a 3 element vector specifying the sky value, 
               the sigma of the sky value, and the number of elements used 
               to compute a sky value.   The 3 element form of SETSKYVAL
               is needed for accurate error budgeting.

 OUTPUTS:
     MAGS   -  NAPER by NSTAR array giving the magnitude for each star in
               each aperture.  (NAPER is the number of apertures, and NSTAR
               is the number of stars).   If the /FLUX keyword is not set, then
               a flux of 1 digital unit is assigned a zero point magnitude of 
               25.
     ERRAP  -  NAPER by NSTAR array giving error for each star.  If a 
               magnitude could not be determined then  ERRAP = 9.99 (if in 
                magnitudes) or ERRAP = !VALUES.F_NAN (if /FLUX is set).
     SKY  -    NSTAR element vector giving sky value for each star in 
               flux units
     SKYERR -  NSTAR element vector giving error in sky values

 EXAMPLE:
       Determine the flux and error for photometry radii of 3 and 5 pixels
       surrounding the position 234.2,344.3 on an image array, im.   Compute
       the partial pixel area exactly.    Assume that the flux units are in
       Poisson counts, so that PHPADU = 1, and the sky value is already known
       to be 1.3, and that the range [-32767,80000] for bad low and bad high
       pixels
      

       IDL> aper, im, 234.2, 344.3, flux, eflux, sky,skyerr, 1, [3,5], -1, $
            [-32767,80000],/exact, /flux, setsky = 1.3
       
 PROCEDURES USED:
       GETOPT, MMM, PIXWT(), STRN(), STRNUMBER()
 NOTES:
       Reasons that a valid magnitude cannot be computed include the following:
      (1) Star position is too close (within 0.5 pixels) to edge of the frame
      (2) Less than 20 valid pixels available for computing sky
      (3) Modal value of sky could not be computed by the procedure MMM
      (4) *Any* pixel within the aperture radius is a "bad" pixel
      (5) The total computed flux is negative.     In this case the negative
          flux and error are returned.


       For the case where the source is fainter than the background, APER will
       return negative fluxes if /FLUX is set, but will otherwise give 
       invalid data (since negative fluxes can't be converted to magnitudes) 
 
       APER was modified in June 2000 in two ways: (1) the /EXACT keyword was
       added (2) the approximation of the intersection of a circular aperture
       with square pixels was improved (i.e. when /EXACT is not used) 
 REVISON HISTORY:
       Adapted to IDL from DAOPHOT June, 1989   B. Pfarr, STX
       FLUX keyword added                       J. E. Hollis, February, 1996
       SETSKYVAL keyword, increase maxsky       W. Landsman, May 1997
       Work for more than 32767 stars           W. Landsman, August 1997
       Don't abort for insufficient sky pixels  W. Landsman  May 2000
       Added /EXACT keyword                     W. Landsman  June 2000 
       Allow SETSKYVAL = 0                      W. Landsman  December 2000 
       Set BADPIX[0] = BADPIX[1] to ignore bad pixels W. L.  January 2001     
       Fix chk_badpixel problem introduced Jan 01 C. Ishida/W.L. February 2001
       Set bad fluxes and error to NAN if /FLUX is set  W. Landsman Oct. 2001 
       Remove restrictions on maximum sky radius W. Landsman  July 2003
       Added /NAN keyword  W. Landsman November 2004
       Set badflux=0 if neither /NAN nor badpix is set  M. Perrin December 2004
       Added READNOISE keyword   W. Landsman January 2005
       Added MEANBACK keyword   W. Landsman October 2005
       Correct typo when /EXACT and multiple apertures used.  W.L. Dec 2005
       Remove VMS-specific code W.L. Sep 2006
       Add additional keywords if /MEANBACK is set W.L  Nov 2006
       Allow negative fluxes if /FLUX is set  W.L.  Mar 2008
       Previous update would crash if first star was out of range  W.L. Mar 2008
       Fix floating equality test for bad magnitudes W.L./J.van Eyken Jul 2009
       Added MINSKY keyword W.L. Dec 2011

(See $IDLUTILS_DIR/goddard/pro/idlphot/aper.pro)

ARCBAR

 NAME:
       ARCBAR
 PURPOSE:
       Draw an arc bar on an image showing the astronomical plate scale

 CALLING SEQUENCE:
       ARCBAR, hdr, arclen,[  COLOR= , /DATA, LABEL= , /NORMAL, POSITION =, 
                              /SECONDS, SIZE=, THICK=, FONT= ]

 INPUTS:
       hdr - image FITS header with astrometry, string array
       arclen - numeric scalar giving length of bar in arcminutes (default)
               or arcseconds (if /SECONDS is set) 

 OPTIONAL KEYWORD INPUTS:
       COLOR - name  or integer scalar specifying the color to draw the arcbar 
               See cgColor for a list of available color names
       /DATA - if set and non-zero, then the POSITION keyword is given in data
              units
       LABEL - string giving user defined label for bar.  Default label is size
               of bar in arcminutes
       /NORMAL - if this keyword is set and non-zero, then POSITION is given in
               normalized units
       POSITION - 2 element vector giving the (X,Y) position in device units 
               (or normalized units if /NORMAL is set, or data units if /DATA
               is set) at which to place the  scale bar.   If not supplied, 
               then the user will be prompted to place the cursor at the 
               desired position
       /SECONDS - if set, then arlen is specified in arcseconds rather than
               arcminutes
       SIZE  - scalar specifying character size of label, default = 1.0
       THICK -  Character thickness of the label, default = !P.THICK
       FONT - scalar font graphics keyword (-1,0 or 1) for text

 EXAMPLE:
       Place a 3' arc minute scale bar, at position 300,200 of the current
       image window, (which is associated with a FITS header, HDR)

       IDL> arcbar, HDR, 3, pos = [300,200]

 RESTRICTIONS:
       When using using a device with scalable pixels (e.g. postscript)
       the data coordinate system must be established before calling ARCBAR.
       If data coordinates are not set, then ARCBAR assumes that the displayed
       image size is given by the NAXIS1 keyword in the FITS header.
 PROCEDURE CALLS:
       AD2XY, EXTAST, GSSSADXY, SXPAR(), cgPlot, cgText
 REVISON HISTORY:
       written by L. Taylor (STX) from ARCBOX (Boothman)
       modified for Version 2 IDL,                     B. Pfarr, STX, 4/91
       New ASTROMETRY structures               W.Landsman,  HSTX, Jan 94
       Recognize a GSSS header                 W. Landsman June 94
       Added /NORMAL keyword                   W. Landsman Feb. 96
       Use NAXIS1 for postscript if data coords not set,  W. Landsman Aug 96
       Fixed typo for postscript W. Landsman   Oct. 96
       Account for zeropoint offset in postscript  W. Landsman   Apr 97
       Added /DATA, /SECONDS keywords   W. Landsman    July 1998
       Use device-independent label offset  W. Landsman   August 2001
       Allow font keyword to be passed.  T. Robishaw Apr. 2006
       Remove obsolete TVCURSOR command  W. Landsman Jul 2007
       Use Coyote Graphics W. Landsman  February 2011

(See $IDLUTILS_DIR/goddard/pro/astro/arcbar.pro)

ARROWS

 NAME:
      ARROWS
 PURPOSE:
      To display "weathervane" directional arrows on an astronomical image 
 EXPLANATION:
      Overlays a graphic showing orientation of North and East.

 CALLING SEQUENCE:
      ARROWS,h, [ xcen, ycen, ARROWLEN= , CHARSIZE=  COLOR= , /DATA
                              FONT=, /NORMAL, /NOTVERTEX, THICK=  ]

 INPUTS:
       h - FITS header array, must include astrometry

 OPTIONAL INPUTS:
       xcen,ycen - numeric scalars, specifying the center position of
		arrows.   Position in device units unless the /NORMALIZED 
		keyword is specified.   If not supplied, then ARROWS
		will prompt for xcen and ycen

 OPTIONAL KEYWORD INPUTS:
       arrowlen  - length of arrows in terms of normal Y size of vector-drawn
                     character,  default  = 3.5, floating point scalar
       charsize  - character size, default = 2.0, floating point scalar
       color     -  color name or number for the arrows and NE letters.  See
                 cgCOLOR() for a list of color names.                    
       Data - if this keyword is set and nonzero, the input center (xcen,
                 ycen) is understood to be in data coordinates
       font - IDL vector font number (1-20) to use to display NE letters.
                 For example, set font=13 to use complex italic font.
       NotVertex - Normally (historically) the specified xcen,ycen indicated
                   the position of the vertex of the figure.  If this
                   keyword is set, the xcen,ycen coordinates refer to a sort
                   of 'center of mass' of the figure.  This allows the
                   figure to always appear with the area irregardless of
                   the rotation angle.
       Normal - if this keyword is set and nonzero, the input center 
                (xcen,ycen) is taken to be in normalized coordinates.   The
                default is device coordinates.
       thick     - line thickness, default = 2.0, floating point scalar
 OUTPUTS:
       none
 EXAMPLE:
       Draw a weathervane at (400,100) on the currently active window, 
       showing the orientation of the image associated with a FITS header, hdr

       IDL> arrows, hdr, 400, 100

 METHOD:
       Uses EXTAST to EXTract ASTrometry from the FITS header.   The 
       directions of North and East are computed and the procedure
       ONE_ARROW called to create the "weathervane".

 PROCEDURES USED:
       GETROT - Computes rotation from the FITS header
       ONE_ARROW - Draw a labeled arrow	
       ZPARCHECK
 REVISON HISTORY:
       written by B. Boothman 2/5/86 
       Recoded with new procedures ONE_ARROW, ONE_RAY.  R.S.Hill,HSTX,5/20/92
       Added separate determination for N and E arrow to properly display
         arrows irregardless of handedness or other peculiarities and added
         /NotVertex keyword to improve positioning of figure. E.Deutsch 1/10/93
       Added /DATA and /NORMAL keywords W. Landsman      July 1993
       Recognize GSSS header    W. Landsman       June 1993
       Added /FONT keyword W. Landsman           April 1995
       Modified to work correctly for COLOR=0  J.Wm.Parker, HITC   1995 May 25
       Work correctly for negative CDELT values   W. Landsman   Feb. 1996
       Use GETROT to compute rotation   W. Landsman    June 2003
       Restored /NotVertex keyword which was not working after June 2003 change
                  W. Landsman  January 2004

(See $IDLUTILS_DIR/goddard/pro/astro/arrows.pro)

ASINH

 NAME:
     ASINH
 PURPOSE:
     Return the inverse hyperbolic sine of the argument
 EXPLANATION:
     The inverse hyperbolic sine is used for the calculation of asinh 
     magnitudes, see Lupton et al. (1999, AJ, 118, 1406)

 CALLING SEQUENCE
     result = asinh( x) 
 INPUTS:
     X - hyperbolic sine, numeric scalar or vector or multidimensional array 
        (not complex) 

 OUTPUT:
     result - inverse hyperbolic sine, same number of elements as X
              double precision if X is double, otherwise floating pt.

 METHOD:
     Expression given in  Numerical Recipes, Press et al. (1992), eq. 5.6.7 
     Note that asinh(-x) = -asinh(x) and that asinh(0) = 0. and that
     if y = asinh(x) then x = sinh(y).     

 REVISION HISTORY:
     Written W. Landsman                 February, 2001
     Work for multi-dimensional arrays  W. Landsman    August 2002
     Simplify coding, and work for scalars again  W. Landsman October 2003

(See $IDLUTILS_DIR/goddard/pro/math/asinh.pro)

ASPECT

 NAME:
  ASPECT

 PURPOSE:

  This function calculates and returns the normalized position
  coordinates necessary to put a plot with a specified aspect ratio
  into the currently active graphics window. It works on the display
  output window as well as in a PostScript output window.

 AUTHOR:

   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:

  Graphics

 CALLING SEQUENCE:

  position = ASPECT(aspectRatio)

 INPUTS:

  aspectRatio: A floating point value that is the desired aspect
     ratio (ratio of heigth to width) of the plot in the current
     graphics output window. If this parameter is missing, an aspect
     ratio of 1.0 (a square plot) is assumed.

 KEYWORD PARAMETERS:

  MARGIN:  The margin around the edges of the plot. The value must be
     a floating point value between 0.0 and 0.5. It is expressed in
     normalized coordinate units. The default margin is 0.15.

  WINDOWASPECT: The aspect ratio of the target window. If not provided,
     the value is obtained from the current graphics window.

 OUTPUTS:

  position: A four-element floating array of normalized coordinates.
     The order of the elements is [x0, y0, x1, y1], similar to the
     !P.POSITION system variable or the POSITION keyword on any IDL
     graphic command.

 EXAMPLE:

  To create a plot with an aspect ratio of 1:2 and a margin of
  0.10 around the edge of the output window, do this:

     plotPosition = ASPECT(0.5, Margin=0.10)
     PLOT, Findgen(11), POSITION=plotPosition

  Notice this can be done in a single IDL command, like this:

     PLOT, Findgen(11), POSITION=ASPECT(0.5, Margin=0.10)

 MODIFICATION HISTORY:

  Written by: David Fanning, November 1996.
       Added better error checking, 18 Feb 1997, DWF.
       Added WindowAspect keyword. 10 Feb 2000. DWF
       Added double precision tolerance for aspectRatio. 9 NOV 2001 BT

(See $IDLUTILS_DIR/goddard/pro/coyote/aspect.pro)

ASTDISP

 NAME:
	ASTDISP

 PURPOSE:
	Print astronomical and pixel coordinates in a standard format
 EXPLANATION:
	This procedure (ASTrometry DISPlay) prints the astronomical and
	pixel coordinates in a standard format.  X,Y must be supplied.  RA,DEC
	may also be supplied, and a data number (DN) may also be 
	supplied.   With use of the Coords= keyword, a string containing the 
	formatted data can be returned in addition or instead (with /silent) 
	of printing.

 CALLING SEQUENCE:
	ASTDISP, x, y, [Ra, Dec, DN, COORD = , /SILENT ]

 INPUT:
	X  - The X pixel coordinate(s), scalar or vector
	Y  - The Y pixel coordinate(s), scalar or vector

 OPTIONAL INPUTS:
	RA -  Right Ascension in *degrees*, scalar or vector
	DEC - DEClination in *degrees*, scalar or vector (if RA is supplied, DEC must also be supplied)
	DN -  Data Number or Flux values

	Each of the inputs X,Y, RA, DEC, DN should have the same number of 
		elements
 OPTIONAL INPUT KEYWORDS:
	SILENT    Prevents printing.  Only useful when used with Coords=
 OUTPUT:
	Printed positions in both degrees and sexigesimal format
	All passed variables remain unchanged
 OPTIONAL KEYWORD OUTPUT:
	COORDS    Returns the formatted coordinates in a string
 PROCEDURES CALLED:
	ADSTRING - used to format the RA and Dec
 HISTORY:
	10-AUG-90 Version 1 written by Eric W. Deutsch
	20-AUG-91 Converted to standard header.  Vectorized Code.  E. Deutsch
	20-NOV-92 Added Coords= and /silent.  E.Deutsch
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/astdisp.pro)

ASTRO

 NAME:
     ASTRO
 PURPOSE:
     Interactive utility for precession and coordinate conversion.

 CALLING SEQUENCE:
     ASTRO, [ selection, EQUINOX =, /FK4]

 OPTIONAL INPUT:
      SELECTION - Scalar Integer (0-6) giving the the particular astronomical
              utility to be used.  (0) Precession, (1) RA, Dec (2000) to Galactic 
              coordinates, (2) Galactic to RA,Dec (2000) (3) RA,Dec (2000) to 
              Ecliptic, (4) Ecliptic to RA, Dec, (5) Ecliptic to Galactic, (6) Galactic
              to Ecliptic.   Program will prompt for SELECTION if this 
              parameter is omitted.

 OPTIONAL KEYWORD INPUT:
       EQUINOX - numeric scalar specifying the equinox to use when converting 
               between celestial and other coordinates.    If not supplied, 
               then the RA and Dec will be assumed to be in EQUINOX J2000.   
               This keyword is ignored by the precession utility.   For 
               example, to convert from RA and DEC (J1975) to Galactic 
               coordinates:

               IDL> astro, 1, E=1975
       /FK4 - If this keyword is set and nonzero, then calculations are done
              in the FK4 system.    For example, to convert from RA and Dec
              (B1975) to Galactic coordinates

               IDL> astro,1, E=1975,/FK4 
 METHOD:
      ASTRO uses PRECESS to compute precession, and EULER to compute
      coordinate conversions.   The procedure GET_COORDS is used to
      read the coordinates, and ADSTRING to format the RA,Dec output.

 NOTES:
      (1) ASTRO temporarily sets !QUIET to suppress compilation messages and
      keep a pretty screen display.   

      (2) ASTRO was changed in December 1998 to use J2000 as the default 
      equinox, **and may be incompatible with earlier calls.***
      
      (3) A nice online page for coordinate conversions is available at
       http://heasarc.gsfc.nasa.gov/cgi-bin/Tools/convcoord/convcoord.pl   
 PROCEDURES USED:
      Procedures: GET_COORDS, EULER       Function: ADSTRING
 REVISION HISTORY
      Written, W. Landsman November 1987
      Code cleaned up       W. Landsman   October 1991
      Added Equinox keyword, call to GET_COORDS, W. Landsman   April, 1992
      Allow floating point equinox input J. Parker/W. Landsman  July 1996
      Make FK5 the default, add FK4 keyword

(See $IDLUTILS_DIR/goddard/pro/astro/astro.pro)

ASTROLIB

 NAME:
       ASTROLIB
 PURPOSE:
       Add the non-standard system variables used by the IDL Astronomy Library
 EXPLANATION: 
       Also defines the environment variable ASTRO_DATA pointing to the 
       directory containing data files  associated with the IDL Astronomy 
       library (system dependent -- user must edit the third line in the
       program below).

 CALLING SEQUENCE:
       ASTROLIB

 INPUTS:
       None.

 OUTPUTS:
       None.

 METHOD:
       The non-standard system variables !PRIV, !TEXTUNIT, and 
       !TEXTOUT are added using DEFSYSV.

 REVISION HISTORY:
       Written, Wayne Landsman, July 1986.
       Use DEFSYSV instead of ADDSYSVAR           December 1990
       Test for system variable existence before definition    July 2001
       Assume since V55, remove VMS support  W. Landsman   Sep 2006
       Remove !Debug, comment out ASTRO_DATA definition  WL  Jan 2009

(See $IDLUTILS_DIR/goddard/pro/misc/astrolib.pro)

AUTOHIST

 NAME:
       AUTOHIST

 PURPOSE:
       Draw a histogram using automatic bin-sizing.
 EXPLANATION
       AUTOHIST chooses a number of bins (initially, SQRT(2*N). If this leads 
       to a histogram in which > 1/5 of the central 50% of the bins are empty,
       it decreases the number of bins and tries again. The minimum # bins is 
       5. The max=199.     Called by HISTOGAUSS and HALFAGAUSS.

 CALLING SEQUENCE:
       AUTOHIST, Sample, XLines, Ylines, XCenters, YCenters, [/NOPLOT, ]
                             ...Plotting Keywords
 INPUT:
       Sample = the vector to be histogrammed

 OUTPUT:
       XLINES = vector of x coordinates of the points that trace the rectangular 
               histogram bins
       YLINES = vector of y coordinates. To draw the histogram plot YLINES vs 
                 XLINES
       XCENTERS = the x values of the bin centers
       YCENTERS = the corresponding y values

 OPTIONAL INPUT KEYWORDS:
       /NOPLOT  If set, nothing is drawn

       Any plotting keywords (e.g. XTITLE) may be supplied to AUTOHIST through
       the _EXTRA facility. 
 REVISION HISTORY:
       Written,   H. Freudenreich, STX, 1/91
       1998 March 17 - Changed shading of histogram.  RSH, RSTX
       V5.0 update, _EXTRA keywords  W. Landsman    April 2002
       Added NOCLIP keyword for POLYFILL call C. Paxson/W. Landsman July 2003
       Use Coyote graphics   W. Landsman  Feb 2011

(See $IDLUTILS_DIR/goddard/pro/robust/autohist.pro)

AVG

 NAME:
       AVG
 PURPOSE:
       Return the average value of an array, or 1 dimension of an array
 EXPLANATION:
       Calculate the average value of an array, or calculate the average
       value over one dimension of an array as a function of all the other
       dimensions.

       In 2009, a DIMENSION keyword was added to the IDL MEAN() function,
       giving it the same capability as AVG().  Thus, the use of AVG() is now
       **deprecated** in favor of the MEAN() function.    
 CALLING SEQUENCE:
       RESULT = AVG( ARRAY, [ DIMENSION, /NAN, /DOUBLE ] )

 INPUTS:
       ARRAY = Input array.  May be any type except string.

 OPTIONAL INPUT PARAMETERS:
       DIMENSION = Optional dimension to do average over, integer scalar

 OPTIONAL KEYWORD INPUT:
      /NAN - Set this keyword to cause the routine to check for occurrences of
            the IEEE floating-point value NaN in the input data.  Elements with
            the value NaN are treated as missing data.
      /DOUBLE - By default, if the input Array is double-precision, complex, 
                or double complex, the result is of the same type;  64 bit
                integers are also returned as double.   Otherwise the result
                the  result is floating-point.   Use of the /DOUBLE keyword 
                forces a double precision output.   Note that internal 
                computations are always done in double precision.
 OUTPUTS:
       The average value of the array when called with one parameter.

       If DIMENSION is passed, then the result is an array with all the
       dimensions of the input array except for the dimension specified,
       each element of which is the average of the corresponding vector
       in the input array.

       For example, if A is an array with dimensions of (3,4,5), then the
       command B = AVG(A,1) is equivalent to

                       B = FLTARR(3,5)
                       FOR J = 0,4 DO BEGIN
                               FOR I = 0,2 DO BEGIN
                                       B[I,J] = TOTAL( A[I,*,J] ) / 4.
                               ENDFOR
                       ENDFOR

 RESTRICTIONS:
       Dimension specified must be valid for the array passed; otherwise the
       input array is returned as the output array.
 PROCEDURE:
       AVG(ARRAY) = TOTAL(ARRAY, /DOUBLE)/N_ELEMENTS(ARRAY) when called with 
       one parameter.
 MODIFICATION HISTORY:
       William Thompson        Applied Research Corporation
       July, 1986              8201 Corporate Drive
                               Landover, MD  20785
       Converted to Version 2      July, 1990
       Replace SUM call with TOTAL    W. Landsman    May, 1992
       Converted to IDL V5.0   W. Landsman   September 1997
       Added /NAN keyword   W. Landsman      July 2000
       Accept a scalar input value    W. Landsman/jimm@berkeley   November 2000
       Internal calculations always in double precision W. Landsman March 2002
       Return NAN if all values in array are NAN  W. Landsman April 2002
       Fixed coding bug if all values in array are NAN W. Landsman Jan 2004

(See $IDLUTILS_DIR/goddard/pro/math/avg.pro)

BARYVEL

 NAME:
       BARYVEL
 PURPOSE:
       Calculates heliocentric and barycentric velocity components of Earth.

 EXPLANATION:
       BARYVEL takes into account the Earth-Moon motion, and is useful for 
       radial velocity work to an accuracy of  ~1 m/s.

 CALLING SEQUENCE:
       BARYVEL, dje, deq, dvelh, dvelb, [ JPL =  ] 

 INPUTS:
       DJE - (scalar) Julian ephemeris date.
       DEQ - (scalar) epoch of mean equinox of dvelh and dvelb. If deq=0
               then deq is assumed to be equal to dje.
 OUTPUTS: 
       DVELH: (vector(3)) heliocentric velocity component. in km/s 
       DVELB: (vector(3)) barycentric velocity component. in km/s

       The 3-vectors DVELH and DVELB are given in a right-handed coordinate 
       system with the +X axis toward the Vernal Equinox, and +Z axis 
       toward the celestial pole.      

 OPTIONAL KEYWORD SET:
       JPL - if /JPL set, then BARYVEL will call the procedure JPLEPHINTERP
             to compute the Earth velocity using the full JPL ephemeris.   
             The JPL ephemeris FITS file JPLEPH.405 must exist in either the 
             current directory, or in the directory specified by the 
             environment variable ASTRO_DATA.   Alternatively, the JPL keyword
             can be set to the full path and name of the ephemeris file.
             A copy of the JPL ephemeris FITS file is available in
                 http://idlastro.gsfc.nasa.gov/ftp/data/         
 PROCEDURES CALLED:
       Function PREMAT() -- computes precession matrix
       JPLEPHREAD, JPLEPHINTERP, TDB2TDT - if /JPL keyword is set
 NOTES:
       Algorithm taken from FORTRAN program of Stumpff (1980, A&A Suppl, 41,1)
       Stumpf claimed an accuracy of 42 cm/s for the velocity.    A 
       comparison with the JPL FORTRAN planetary ephemeris program PLEPH
       found agreement to within about 65 cm/s between 1986 and 1994

       If /JPL is set (using JPLEPH.405 ephemeris file) then velocities are 
       given in the ICRS system; otherwise in the FK4 system.   
 EXAMPLE:
       Compute the radial velocity of the Earth toward Altair on 15-Feb-1994
          using both the original Stumpf algorithm and the JPL ephemeris

       IDL> jdcnv, 1994, 2, 15, 0, jd          ;==> JD = 2449398.5
       IDL> baryvel, jd, 2000, vh, vb          ;Original algorithm
               ==> vh = [-17.07243, -22.81121, -9.889315]  ;Heliocentric km/s
               ==> vb = [-17.08083, -22.80471, -9.886582]  ;Barycentric km/s
       IDL> baryvel, jd, 2000, vh, vb, /jpl   ;JPL ephemeris
               ==> vh = [-17.07236, -22.81126, -9.889419]  ;Heliocentric km/s
               ==> vb = [-17.08083, -22.80484, -9.886409]  ;Barycentric km/s

       IDL> ra = ten(19,50,46.77)*15/!RADEG    ;RA  in radians
       IDL> dec = ten(08,52,3.5)/!RADEG        ;Dec in radians
       IDL> v = vb[0]*cos(dec)*cos(ra) + $   ;Project velocity toward star
               vb[1]*cos(dec)*sin(ra) + vb[2]*sin(dec) 

 REVISION HISTORY:
       Jeff Valenti,  U.C. Berkeley    Translated BARVEL.FOR to IDL.
       W. Landsman, Cleaned up program sent by Chris McCarthy (SfSU) June 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Added /JPL keyword  W. Landsman   July 2001
       Documentation update W. Landsman Dec 2005

(See $IDLUTILS_DIR/goddard/pro/astro/baryvel.pro)

BITGET

 NAME:
       BITGET

 PURPOSE:

       Returns the bit value (0 or 1) of a specified bit in a supplied number.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Utilities

 CALLING SEQUENCE:

       bitValue = BitGet(number, bit)

 INPUT_PARAMETERS:

       number:          The input number. Should be a scalar integer. If not, it is converted to
                        one by rounding.

       bit:             The number of the bit you are interested in. A value between 0 and 63.
                        If not supplied, all 64 bit values of the number are returned. May be
                        an array of bit numbers.

 OUTPUT_PARAMETERS:

      bitValue:        The value, 0 or 1, of the specified bit in the number.

 KEYWORDS:

     SILENT:           If set, suppresses informational messages regarding rounding operations.

 MODIFICATION HISTORY:

       Written by David W. Fanning, 14 June 2006.

(See $IDLUTILS_DIR/goddard/pro/coyote/bitget.pro)

BIWEIGHT_MEAN

 NAME:
	BIWEIGHT_MEAN 

 PURPOSE:
	Calculate the center and dispersion (like mean and sigma) of a 
	distribution using bisquare weighting.

 CALLING SEQUENCE:
	Mean = BIWEIGHT_MEAN( Vector, [ Sigma, Weights ] ) 

 INPUTS:
	Vector = Distribution in vector form

 OUTPUT:
	Mean - The location of the center.

 OPTIONAL OUTPUT ARGUMENTS:

	Sigma = An outlier-resistant measure of the dispersion about the 
	      center, analogous to the standard deviation. 

	Weights = The weights applied to the data in the last iteration, 
                 floating point vector

 NOTES:
       Since a sample mean  scaled by sigma/sqrt(N), has a Student's T 
       distribution, the half-width of the  95% confidence interval for 
       the sample mean  can be determined as follows: 
          ABS( T_CVF( .975, .7*(N-1) )*SIGMA/SQRT(N) ) 
       where N = number of  points, and  0.975 = 1 - (1 - 0.95)/2. 
 PROCEDURES USED:
       ROBUST_SIGMA()
 REVISION HISTORY
	Written,  H. Freudenreich, STX, 12/89
	Modified 2/94, H.T.F.: use a biweighted standard deviation rather than
		median absolute deviation.
	Modified 2/94, H.T.F.: use the fractional change in SIGMA as the 
		convergence criterion rather than the change in center/SIGMA.
       Modified May 2002  Use MEDIAN(/EVEN)
       Modified October 2002, Faster computation of weights 
       Corrected documentation on 95% confidence interval of mean 
                 P.Broos/W. Landsman   July 2003

(See $IDLUTILS_DIR/goddard/pro/robust/biweight_mean.pro)

BLINK

 NAME:
	BLINK
 PURPOSE:
	To allow the user to alternatively examine two or more windows within
	a single window.

 CALLING SEQUENCE:
	BLINK, Wndw [, T]

 INPUTS:
	Wndw  A vector containing the indices of the windows to blink.
	T     The time to wait, in seconds, between blinks.  This is optional
	      and set to 1 if not present.  

 OUTPUTS:
	None.

 PROCEDURE:
	The images contained in the windows given are written to a pixmap.
	The contents of the the windows are copied to a display window, in 
	order, until a key is struck.

 EXAMPLE:
	Blink windows 0 and 2 with a wait time of 3 seconds

	IDL> blink, [0,2], 3 

 MODIFICATION HISTORY:
	Written by Michael R. Greason, STX, 2 May 1990.
	Allow different size windows   Wayne Landsman    August, 1991
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/tv/blink.pro)

BLKSHIFT

 NAME:
   BLKSHIFT

 AUTHOR:
   Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
   craigm@lheamail.gsfc.nasa.gov

 PURPOSE:
   Shift a block of data to a new position in a file (possibly overlapping)

 CALLING SEQUENCE:

   BLKSHIFT, UNIT, POS, [ DELTA, TO=TO, /NOZERO, ERRMSG=ERRMSG, 
             BUFFERSIZE=BUFFERSIZE ]

 DESCRIPTION:

  BLKSHIFT moves a block of data forward or backward, to a new
  position in a data file.  The old and new positions of the block
  can overlap safely.

  The new position can be specified with either the DELTA parameter,
  which gives the number of bytes to move forward (positive delta) or
  backward (negative delta); or the TO keyword, which give the new
  absolute starting position of the block.

  The block can be moved beyond the current end of file point, in
  which case the intervening gap is filled with zeros (optionally).
  The gap left at the old position of the block is also optionally
  zero-filled.    If a set of data up to the end of the file is being
  moved forward (thus making the file smaller) then
  the file is truncated at the new end.using TRUNCATE_LUN.

 INPUTS:

   UNIT - a logical unit number, opened for reading and writing.

   POS - POS[0] is the position of the block in the file, in bytes,
         before moving.  POS[1], if present, is the size of the block
         in bytes.  If POS[1] is not given, then the block is from
         POS[0] to the end of the file.

   DELTA - the (optional) offset in bytes between the old and new
           positions, from the start of the block.  Positive values
           indicate moving the data forward (toward the end of file),
           and negative values indicate moving the data backward
           (toward the beginning of the file).  One of DELTA and TO
           must be specified; DELTA overrides the TO keyword.

           Attempts to move the block beyond the end of the file will
           succeed.  A block can never be moved beyond the beginning
           of the file; it will be moved to the beginning instead.

 KEYWORD PARAMETERS:

   TO - the absolute file offset in bytes for the new start of the
        block.  One of DELTA and TO must be specified; DELTA
        overrides the TO keyword.

   /NOZERO - if set, then newly created gaps will not be explicitly
            zeroed.   Note that in same systems (e.g. MacOS) the gaps will
            always be zeroed whether or not /NOZERO is set.

   ERRMSG - If defined and passed, then any error messages will be
            returned to the user in this parameter rather than
            depending on the MESSAGE routine in IDL.  If no errors
            are encountered, then a null string is returned.  

			BLKSHIFT, UNIT, POS, DElTA, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

   BUFFERSIZE - the maximum buffer size for transfers, in bytes.
                Larger values of this keyword impose larger memory
                requirements on the application; smaller values will
                lead to more transfer operations.
                Default: 32768 (bytes)

 MODIFICATION HISTORY:

   Written, CM, Apr 2000
   Documented and re-written, CM, 20 Jul 2000
   Renamed from FXSHIFT to BLKSHIFT, CM, 21 Jul 2000
   Documentation, CM, 12 Dec 2002
   Truncate if moving data block forward from  the end of file 
             using TRUNCATE_LUN   W. Landsman Feb. 2005 
   Assume since V5.5, remove VMS support  W. Landsman  Sep 2006
   Assume since V5.6, TRUNCATE_LUN available  W. Landsman Sep 2006
   MacOS can point beyond EOF    W. Landsman   Aug 2009

(See $IDLUTILS_DIR/goddard/pro/misc/blkshift.pro)

BOOST_ARRAY

 NAME:
	BOOST_ARRAY
 PURPOSE:
	Append one array onto a destination array
 EXPLANATION:
	Add array APPEND to array DESTINATION, allowing the dimensions of
	DESTINATION to adjust to accommodate it.  If both input arrays have the
	same number of dimensions, then the output array will have one
	additional dimension.  Otherwise, the last dimension of DESTINATION
	will be incremented by one.
 CATEGORY:
	Utility
 CALLING SEQUENCE:
	BOOST_ARRAY, DESTINATION, APPEND
 INPUT:
	DESTINATION	= Array to be expanded.
	APPEND		= Array to append to DESTINATION.
 OUTPUTS:
	DESTINATION	= Expanded output array.
 RESTRICTIONS:
	DESTINATION and APPEND have to be either both of type string or both of
	numerical types.

	APPEND cannot have more dimensions than DESTINATION.

 MODIFICATION HISTOBY:
	Written Aug'88 (DMZ, ARC)
	Modified Sep'89 to handle byte arrays (DMZ)
	Modifed to version 2, Paul Hick (ARC), Feb 1991
	Removed restriction to 2D arrays, William Thompson (ARC), Feb 1992.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/boost_array.pro)

BOXAVE

 NAME:
       BOXAVE
 PURPOSE:
       Box-average a 1 or 2 dimensional array.   
 EXPLANATION:
       This procedure differs from the intrinsic REBIN function in the follow 
       2 ways: 

       (1) the box size parameter is specified rather than the output 
               array size
       (2) for INTEGER arrays, BOXAVE computes intermediate steps using REAL*4 
               (or REAL*8 for 64bit integers) arithmetic.   This is 
               considerably slower than REBIN but avoids integer truncation

 CALLING SEQUENCE:
       result = BOXAVE( Array, Xsize,[ Ysize ] )     

 INPUTS:
       ARRAY - Two dimensional input Array to be box-averaged.  Array may be 
               one or 2 dimensions and of any type except character.   

 OPTIONAL INPUTS:
       XSIZE - Size of box in the X direction, over which the array is to
               be averaged.  If omitted, program will prompt for this 
               parameter.  
       YSIZE - For 2 dimensional arrays, the box size in the Y direction.
               If omitted, then the box size in the X and Y directions are 
               assumed to be equal

 OUTPUT:
       RESULT - Output array after box averaging.  If the input array has 
               dimensions XDIM by YDIM, then RESULT has dimensions
               XDIM/NBOX by YDIM/NBOX.  The type of RESULT is the same as
               the input array.  However, the averaging is always computed
               using REAL arithmetic, so that the calculation should be exact.
               If the box size did not exactly divide the input array, then
               then not all of the input array will be boxaveraged.

 PROCEDURE:
       BOXAVE boxaverages all points simultaneously using vector subscripting

 NOTES:
       If im_int is a 512 x 512 integer array, then the two statements

               IDL> im = fix(round(rebin(float(im_int), 128, 128)))
               IDL> im  = boxave( im_int,4)

       give equivalent results.   The use of REBIN is faster, but BOXAVE is
       is less demanding on virtual memory, since one does not need to make
       a floating point copy of the entire array.      

 REVISION HISTORY:
       Written, W. Landsman, October 1986
       Call REBIN for REAL*4 and REAL*8 input arrays, W. Landsman Jan, 1992
       Removed /NOZERO in output array definition     W. Landsman 1995
       Fixed occasional integer overflow problem      W. Landsman Sep. 1995
       Allow unsigned data types                      W. Landsman Jan. 2000
       Assume since V5.4, Allow 64bit integers        W. Landsman Apr  2006

(See $IDLUTILS_DIR/goddard/pro/image/boxave.pro)

BPRECESS

 NAME:
       BPRECESS
 PURPOSE:
       Precess positions from J2000.0 (FK5) to B1950.0 (FK4)
 EXPLANATION:
       Calculates the mean place of a star at B1950.0 on the FK4 system from
       the mean place at J2000.0 on the FK5 system.    

 CALLING SEQUENCE:
       bprecess, ra, dec, ra_1950, dec_1950, [ MU_RADEC = , PARALLAX = 
                                       RAD_VEL =, EPOCH =   ]

 INPUTS:
       RA,DEC - Input J2000 right ascension and declination in *degrees*.
               Scalar or N element vector

 OUTPUTS:
       RA_1950, DEC_1950 - The corresponding B1950 right ascension and 
               declination in *degrees*.    Same number of elements as
               RA,DEC but always double precision.

 OPTIONAL INPUT-OUTPUT KEYWORDS
       MU_RADEC - 2xN element double precision vector containing the proper 
                  motion in seconds of arc per tropical *century* in right 
                  ascension and declination.
       PARALLAX - N_element vector giving stellar parallax (seconds of arc)
       RAD_VEL  - N_element vector giving radial velocity in km/s

       The values of MU_RADEC, PARALLAX, and RADVEL will all be modified
       upon output to contain the values of these quantities in the
       B1950 system.  The parallax and radial velocity will have a very 
       minor influence on the B1950 position.   

       EPOCH - scalar giving epoch of original observations, default 2000.0d
           This keyword value is only used if the MU_RADEC keyword is not set.
 NOTES:
       The algorithm is taken from the Explanatory Supplement to the 
       Astronomical Almanac 1992, page 186.
       Also see Aoki et al (1983), A&A, 128,263

       BPRECESS distinguishes between the following two cases:
       (1) The proper motion is known and non-zero
       (2) the proper motion is unknown or known to be exactly zero (i.e.
               extragalactic radio sources).   In this case, the reverse of 
               the algorithm in Appendix 2 of Aoki et al. (1983) is used to 
               ensure that the output proper motion is  exactly zero. Better 
               precision can be achieved in this case by inputting the EPOCH 
               of the original observations.

       The error in using the IDL procedure PRECESS for converting between
       B1950 and J1950 can be up to 12", mainly in right ascension.   If
       better accuracy than this is needed then BPRECESS should be used.

       An unsystematic comparison of BPRECESS with the IPAC precession 
       routine (http://nedwww.ipac.caltech.edu/forms/calculator.html) always 
       gives differences less than 0.15".
 EXAMPLE:
       The SAO2000 catalogue gives the J2000 position and proper motion for
       the star HD 119288.   Find the B1950 position. 

       RA(2000) = 13h 42m 12.740s      Dec(2000) = 8d 23' 17.69''  
       Mu(RA) = -.0257 s/yr      Mu(Dec) = -.090 ''/yr

       IDL> mu_radec = 100D* [ -15D*.0257, -0.090 ]
       IDL> ra = ten(13, 42, 12.740)*15.D 
       IDL> dec = ten(8, 23, 17.69)
       IDL> bprecess, ra, dec, ra1950, dec1950, mu_radec = mu_radec
       IDL> print, adstring(ra1950, dec1950,2)
               ===> 13h 39m 44.526s    +08d 38' 28.63"

 REVISION HISTORY:
       Written,    W. Landsman                October, 1992
       Vectorized, W. Landsman                February, 1994
       Treat case where proper motion not known or exactly zero  November 1994
       Handling of arrays larger than 32767   Lars L. Christensen, march, 1995
       Fixed bug where A term not initialized for vector input 
            W. Landsman        February 2000
       Use V6.0 notation  W. Landsman Mar 2011

(See $IDLUTILS_DIR/goddard/pro/astro/bprecess.pro)

BREAK_PATH()

 NAME: 
    BREAK_PATH()

 PURPOSE: 
     Breaks up a path string into its component directories.

 CALLING SEQUENCE: 
     Result = BREAK_PATH( PATHS [ /NoCurrent])

 INPUTS: 
     PATHS   = A string containing one or more directory paths.  The
               individual paths are separated by commas, although in UNIX, 
               colons can also be used.  In other words, PATHS has the same 
               format as !PATH, except that commas can be used as a separator 
               regardless of operating system.

               A leading $ can be used in any path to signal that what follows 
               is an environmental variable, but the $ is not necessary.    
               Environmental variables can themselves contain multiple paths.

 OUTPUT: 
      The result of the function is a string array of directories.
      Unless the NOCURRENT keyword is set, the first element of the array is 
      always the null string, representing the current directory.  All the 
      other directories will end in the correct separator character for the 
      current operating system.

 OPTIONAL INPUT KEYWORD:
      /NOCURRENT = If set, then the current directory (represented by
               the null string) will not automatically be prepended to the
               output.

 PROCEDURE CALLS:
      None.

 REVISION HISTORY:
       Version 1, William Thompson, GSFC, 6 May 1993.
               Added IDL for Windows compatibility.
       Version 2, William Thompson, GSFC, 16 May 1995
               Added keyword NOCURRENT
       Version 3, William Thompson, GSFC, 29 August 1995
               Modified to use OS_FAMILY
       Version 4, Zarro, GSFC, 4 August 1997
               Added trim to input
       Fix directory character on Macintosh system   A. Ferro   February 2000
       Use STRSPLIT instead of STR_SEP()   W. Landsman    July 2002
       Remove VMS support    W. Landsman   September 2006

(See $IDLUTILS_DIR/goddard/pro/misc/break_path.pro)

BSORT

 NAME:
       BSORT
 PURPOSE:
       Function to sort data into ascending order, like a simple bubble sort.
 EXPLANATION:
       Original subscript order is maintained when values are equal (FIFO).
       (This differs from the IDL SORT routine alone, which may rearrange 
       order for equal values)

       A faster algorithm (radix sort) for numeric data is available  at 
       http://idldatapoint.com/2012/04/19/an-lsd-radix-sort-algorithm-in-idl/
 CALLING SEQUENCE:  
       result = bsort( array, [ asort, /INFO, /REVERSE ] )

 INPUT:
       Array - array to be sorted

 OUTPUT:
       result - sort subscripts are returned as function value

 OPTIONAL OUTPUT:
       Asort - sorted array

 OPTIONAL KEYWORD INPUTS:
       /REVERSE - if this keyword is set, and non-zero, then data is sorted
                 in descending order instead of ascending order.
       /INFO = optional keyword to cause brief message about # equal values.

 HISTORY
       written by F. Varosi Oct.90:
       uses WHERE to find equal clumps, instead of looping with IF ( EQ ).
       compatible with string arrays, test for degenerate array 
       20-MAY-1991     JKF/ACC via T AKE- return indexes if the array to 
                       be sorted has all equal values.
       Aug - 91  Added  REVERSE keyword   W. Landsman      
       Always return type LONG    W. Landsman     August 1994
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/bsort.pro)

CALZ_UNRED

 NAME:
     CALZ_UNRED
 PURPOSE:
     Deredden a galaxy spectrum using the Calzetti et al. (2000) recipe
 EXPLANATION:
     Calzetti et al.  (2000, ApJ 533, 682) developed a recipe for dereddening 
     the spectra of galaxies where massive stars dominate the radiation output,
     valid between 0.12 to 2.2 microns.     (CALZ_UNRED extrapolates between
     0.12 and 0.0912 microns.)   

 CALLING SEQUENCE:
     CALZ_UNRED, wave, flux, ebv, [ funred, R_V = ]
 INPUT:
      WAVE - wavelength vector (Angstroms)
      FLUX - calibrated flux vector, same number of elements as WAVE
               If only 3 parameters are supplied, then this vector will
               updated on output to contain the dereddened flux.
      EBV  - color excess E(B-V), scalar.  If a negative EBV is supplied,
               then fluxes will be reddened rather than deredenned.
               Note that the supplied color excess should be that derived for 
               the stellar  continuum, EBV(stars), which is related to the 
               reddening derived from the gas, EBV(gas), via the Balmer 
               decrement by EBV(stars) = 0.44*EBV(gas)

 OUTPUT:
      FUNRED - unreddened flux vector, same units and number of elements
               as FLUX.   FUNRED values will be zeroed outside valid domain
               Calz_unred (0.0912 - 2.2 microns).
           
 OPTIONAL INPUT KEYWORD:
       R_V - Ratio of total to selective extinction, default = 4.05.  
             Calzetti et al. (2000) estimate R_V = 4.05 +/- 0.80 from optical
             -IR observations of 4 starbursts.
 EXAMPLE:
       Estimate how a flat galaxy spectrum (in wavelength) between 1200 A 
       and 3200 A is altered by a reddening of E(B-V) = 0.1.   

       IDL> w = 1200 + findgen(40)*50      ;Create a wavelength vector
       IDL> f = w*0 + 1                    ;Create a "flat" flux vector
       IDL> calz_unred, w, f, -0.1, fnew  ;Redden (negative E(B-V)) flux vector
       IDL> plot,w,fnew                   

 NOTES:
       Use the 4 parameter calling sequence if you wish to save the 
               original flux vector.
 PROCEDURE CALLS:
      POLY()
 REVISION HISTORY:
       Written   W. Landsman        Raytheon  ITSS   December, 2000

(See $IDLUTILS_DIR/goddard/pro/astro/calz_unred.pro)

CCM_UNRED

 NAME:
     CCM_UNRED
 PURPOSE:
     Deredden a flux vector using the CCM 1989 parameterization 
 EXPLANATION:
     The reddening curve is that of Cardelli, Clayton, and Mathis (1989 ApJ.
     345, 245), including the update for the near-UV given by O'Donnell 
     (1994, ApJ, 422, 158).   Parameterization is valid from the IR to the 
     far-UV (3.5 microns to 0.1 microns).    

     Users might wish to consider using the alternate procedure FM_UNRED
     which uses the extinction curve of Fitzpatrick (1999).
 CALLING SEQUENCE:
     CCM_UNRED, wave, flux, ebv, funred, [ R_V = ]      
             or 
     CCM_UNRED, wave, flux, ebv, [ R_V = ]      
 INPUT:
     WAVE - wavelength vector (Angstroms)
     FLUX - calibrated flux vector, same number of elements as WAVE
             If only 3 parameters are supplied, then this vector will
             updated on output to contain the dereddened flux.
     EBV  - color excess E(B-V), scalar.  If a negative EBV is supplied,
             then fluxes will be reddened rather than deredenned.

 OUTPUT:
     FUNRED - unreddened flux vector, same units and number of elements
             as FLUX

 OPTIONAL INPUT KEYWORD
     R_V - scalar specifying the ratio of total selective extinction
             R(V) = A(V) / E(B - V).    If not specified, then R_V = 3.1
             Extreme values of R(V) range from 2.75 to 5.3

 EXAMPLE:
     Determine how a flat spectrum (in wavelength) between 1200 A and 3200 A
     is altered by a reddening of E(B-V) = 0.1.   Assume an "average"
     reddening for the diffuse interstellar medium (R(V) = 3.1)

       IDL> w = 1200 + findgen(40)*50      ;Create a wavelength vector
       IDL> f = w*0 + 1                    ;Create a "flat" flux vector
       IDL> ccm_unred, w, f, -0.1, fnew  ;Redden (negative E(B-V)) flux vector
       IDL> plot,w,fnew                   

 NOTES:
     (1) The CCM curve shows good agreement with the Savage & Mathis (1979)
             ultraviolet curve shortward of 1400 A, but is probably
             preferable between 1200 and 1400 A.
     (2)  Many sightlines with peculiar ultraviolet interstellar extinction 
             can be represented with a CCM curve, if the proper value of 
             R(V) is supplied.
     (3)  Curve is extrapolated between 912 and 1000 A as suggested by
             Longo et al. (1989, ApJ, 339,474)
     (4) Use the 4 parameter calling sequence if you wish to save the 
               original flux vector.
     (5) Valencic et al. (2004, ApJ, 616, 912) revise the ultraviolet CCM
             curve (3.3 -- 8.0 um-1).    But since their revised curve does
             not connect smoothly with longer and shorter wavelengths, it is
             not included here.

 REVISION HISTORY:
       Written   W. Landsman        Hughes/STX   January, 1992
       Extrapolate curve for wavelengths between 900 and 1000 A   Dec. 1993
       Use updated coefficients for near-UV from O'Donnell   Feb 1994
       Allow 3 parameter calling sequence      April 1998
       Converted to IDLV5.0                    April 1998

(See $IDLUTILS_DIR/goddard/pro/astro/ccm_unred.pro)

CENTERTLB

 NAME:
       CENTERTLB

 PURPOSE:

       This is a utility routine to position a widget program
       on the display at an arbitrary location. By default the
       widget is centered on the display.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Utilities

 CALLING SEQUENCE:

       CenterTLB, tlb, [x, y, /NOCENTER, /DEVICE, CENTERONTLB=wOtherTLBID]

 REQUIRED INPUTS:

       tlb: The top-level base identifier of the widget program. This must
       be a valid widget ID.

 OPTIONAL INPUTS:

       x:  Set this equal to a normalized position for the center
       of the widget as measured from the left-hand side of the screen.
       The default value is 0.5 (the center)  Setting this equal to 1.0
       places the widget at the far right-hand side of the screen.

       y:  Set this equal to a normalized position for the center
       of the widget as measured from the bottom of the screen.
       The default value is 0.5 (the center) Setting this equal to 1.0
       places the widget at the top of the screen.

 KEYWORDS:

      DEVICE:  Normally, the x and y parameters are specified in normalized
      coordinates. If this keyword is set, they are taken to be in DEVICE
      coordinates.

      NOCENTER:  By default, the center of the widget is positioned at the
      location specified by the x and y parameters.  If NOCENTER is set
      to a non-zero value, then the upper left corner of the widget
      is postioned at the specifed location.
      
      CENTERONTLB:  If provided, the center of the widget is positioned at 
      the center of the widget whose ID is provided here.

 PROCEDURE:

       The program should be called after all the widgets have
       been created, but just before the widget hierarchy is realized.
       It uses the top-level base geometry along with the display size
       to calculate offsets for the top-level base that will center the
       top-level base on the display.

 COMMENT:
       Regardless of the values set for x, y and NOCENTER, the widget
       is not permitted to run off the display.

 MODIFICATION HISTORY:

       Written by:  Dick Jackson, 12 Dec 98.
       Modified to use device-independent Get_Screen_Size
            function. 31 Jan 2000. DWF.
       Added x, y, NOCENTER and run-off protection. 26 Jan 2001. BT.
       Added a maximum value of 1280 for X screen size. This helps
            center the widget on a single monitor when using dual
            monitor settings with some graphics cards. 3 Feb 2003. DWF.
       Added DEVICE keyword. 4 January 2006. DWF.
       Added CenterOnTLB keyword. 7 March 2011. DJ.

(See $IDLUTILS_DIR/goddard/pro/coyote/centertlb.pro)

CGAXIS

 Provides a device-independent and color-model-independent way to draw an axis into
 a graphics window. It is a wrapper to the AXIS command.
 
 The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
 to be installed on your machine.

 :Categories:
    Graphics
    
 :Params:
    xloc: in, optional, type=depends
       The X location of the axis. 
    yloc: in, optional, type=depends
       The Y location of the axis. 
    zloc: in, optional, type=depends
       The Z location of the axis. 
       
 :Keywords:
     charsize: in, optional, type=float, default=cgDefCharSize()
         The character size for axes annotations. Uses cgDefCharSize to select default
         character size, unless !P.Charsize is set, in which case !P.Charsize is always used.
     color: in, optional, type=string/integer/long
         The color of the text. Color names are those used with cgColor. By default,
         "black", unless the upper-right hand pixel in the display is black, then "white".
     data: in, optional, type=boolean
         Set this keyword to indicate xloc and yloc are in data coordinates. Data coordinates
         are the default, unless DEVICE or NORMAL is set.
     device: in, optional, type=boolean
         Set this keyword to indicate xloc and yloc are in device coordinates.
     font: in, optional, type=integer, default=!P.Font
         The type of font desired. By default, !P.Font.
     normal: in, optional, type=boolean
         Set this keyword to indicate xloc and yloc are in normalized coordinates.
     save: in, optional, type=boolean
         Set this keyword to save the scaling parameters set by the axis for subsequent use.
     t3d: in, optional, type=boolean, default=0
         Set this keyword to rotate the axis is the 3D data space set up with !P.T.
     title: in, optional, type=string, default=""
         The title or annotation that appears on the axis.
     window: in, optional, type=boolean
         Set this keyword to add the command to the in the current cgWindow application.
     xaxis: in, optional, type=integer, default=0
         If set to 0, the axis is drawn under the plot with the tick marks pointing up; if set 
         to 1, the axis is drawn on top of the plot with the tick marks pointing down.
     xlog: in, optional, type=boolean, default=0
         Set this keyword to specify a logarithmic axis type.
     xtitle: in, optional, type=string
         An alternative way to set the `Title` keyword for X axes. Use `Title` instead.
     yaxis: in, optional, type=integer, default=0
         If set to 0, the axis is drawn on the left of the plot with the tick marks pointing 
         to the right. If set to 1, the axis is drawn on the right of the plot with the tick 
         marks pointing to the left.
     ylog: in, optional, type=boolean, default=0
         Set this keyword to specify a logarithmic axis type.
     ynozero: in, optional, type=boolean, default=0
         Set this keyword to prevent the Y axis from starting at 0.
     ytitle: in, optional, type=string
         An alternative way to set the `Title` keyword for Y axes. Use `Title` instead.
     zaxis: in, optional, type=integer, default=0
         Set to 0-3 to position the Z axis in various locatons. See the AXIS documentation.
     zlog: in, optional, type=boolean, default=0
         Set this keyword to specify a logarithmic axis type.
     ztitle: in, optional, type=string
         An alternative way to set the `Title` keyword for Z axes. Use `Title` instead.
     _ref_extra: in, optional
          Any keywords appropriate for the AXIS command.
     
          
 :Examples:
    Used like the IDL AXIS command::
       IDL> cgPlot, cgDemoData(1), YStyle=8, Position=[0.1, 0.1, 0.85, 0.9], /Window
       IDL> cgAxis, /YAxis, Color='red', YRange=[-500, 500], /Save, /Window
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 25 Janauray 2011. DWF.
        Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF
        Modifed the way I am handling brain dead AXIS command. 30 May 2011. DWF.
        Modified to use cgDefaultColor for default color selection. 24 Dec 2011. DWF.
        Added T3D keyword. 1 March 2012. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgaxis.pro)

CGCOLORFILL

 Provides a device-independent and color-model-independent way to fill a polygon
 with a particular color. This is a wrapper to the PolyFill command in IDL.
 
 The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
 to be installed on your machine.

 :Categories:
    Graphics
    
 :Params:
     x: in, required, type=number
         A vector argument providing the X coordinates of the points to be connected. 
         The vector must contain at least three elements. If only one argument is 
         specified, X must be an array of either two or three vectors (i.e., (2,*) 
         or (3,*)). In this special case, the vector X[0,*] specifies the X values, 
         X[1,*] specifies Y, and X[2,*] contain the Z values.       
     y: in, required, type=number
         A vector argument providing the Y coordinates of the points to be connected. 
         Y must contain at least three elements.
     z: in, optional, type=number
         An optional vector argument providing the Z coordinates of the points to be 
         connected. Z must contain at least three elements.

 :Keywords:
     color: in, optional, type=string/integer/long, default='rose'
         The name of the fill color. Color names are those used with cgColor. 
         This value can also be a long integer or an index into the current color
         table.
     device: in, optional, type=boolean, default=0
         Set to indicate the polygon vertices are in device coordinates.
     normal: in, optional, type=boolean, default=0
         Set to indicate the polygon vertices are in normalized coordinates.
     window: in, optional, type=boolean, default=0
         Set this keyword to add the command to the current cgWindow application.
     _ref_extra: in, optional, type=appropriate
         Any other keywords to the IDL POLYFILL command may be used.
     
          
 :Examples:
    Used like the IDL Polyfill command::
       IDL> cgColorFill, [0.25, 0.25, 0.75, 0.75, 0.25], [0.25, 0.75, 0.75, 0.25, 0.25], $
                 /NORMAL, COLOR='blue'
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 24 December 2010. DWF.
        In some cases, I was turning BYTE values to strings without converting to 
            INTEGERS first. 30 Dec 2010. DWF.        
        Moved setting to decomposed color before color selection process to avoid PostScript
             background problems when passed 24-bit color integers. 12 Jan 2011. DWF.   
        Added WINDOW keyword. 24 Jan 2011. DWF.
        Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF
        Modified to use cgDefaultColor for default color selection. 24 Dec 2011. DWF.

 :Copyright:
     Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgcolorfill.pro)

CGCOLOR[1]

The purpose of this function is to obtain drawing colors
by name and in a device/decomposition independent way.
The color names and values may be read in as a file, or 192 color
names and values are supplied with the program. These colors were
obtained from the file rgb.txt, found on most X-Window distributions,
and from colors in the `Brewer color tables <http://colorbrewer2.org/>`.
Representative colors were chosen from across the color spectrum.
If the color names '0', '1', '2', ..., '255' are used, they will
correspond to the colors in the current color table in effect at
the time the `cgColor` program is called.

The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
to be installed on your machine.

:Categories:
Graphics

:Examples:
To get drawing colors in a device-decomposed independent way::

axisColor = cgColor("Green", !D.Table_Size-2)
backColor = cgColor("Charcoal", !D.Table_Size-3)
dataColor = cgColor("Yellow", !D.Table_Size-4)
Plot, Findgen(11), Color=axisColor, Background=backColor, /NoData
OPlot, Findgen(11), Color=dataColor

To set the viewport color in object graphics::

theView = Obj_New('IDLgrView', Color=cgColor('Charcoal', /Triple))

To change the viewport color later::

theView->SetProperty, Color=cgColor('Antique White', /Triple)

To load the drawing colors "red", "green", and "yellow" at indices 100-102, type this::

IDL> TVLCT, cgColor(["red", "green", "yellow"], /Triple), 100

To interactively choose a color, set the SELECTCOLOR keyword::

IDL> color = cgColor(/SelectColor)

The PickColorName program is a good way to learn the names of the colors available::

IDL> color = PickColorName()

:Author:
FANNING SOFTWARE CONSULTING::
David W. Fanning
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: david@idlcoyote.com
Coyote's Guide to IDL Programming: http://www.idlcoyote.com

:History:
Change History::
Written by: David W. Fanning
Modified FSC_COLOR to create cgColor 9 February 2011. DWF.
Modified to allow a three-element color triple to be used in place of the color
name parameter. This allows one user-defined color to be used. 4 Dec 2011. DWF.
Modified to allow byte and 16-bit integer values to be used to specify colors
in the current color table. 5 Dec 2011. DWF.
Modified to allow the "opposite" pixel to be determined in the Z-graphics buffer. 24 Dec 2011. DWF.
Modified the code to handle long integers depending on the current color mode and the
number of values passed in. 10 January 2012. DWF.
Made sure the return values are BYTES not INTEGERS, in cases where this is expected. 10 Jan 2012. DWF.
Added "Background" as a color name. The opposite of "Opposite". 1 Feb 2012. DWF.
When returning a vector of color values, now making sure to return a byte array if
in indexed color mode. 27 Feb 2012. DWF.

:Copyright:
Copyright (c) 2009-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgcolor.pro)

CGCOLOR[2]

+
 This function accepts a [red, green, blue] triple that
 describes a particular color and returns a 24-bit long
 integer that is equivalent to (can be decomposed into)
 that color. 
 
 :Params:
    color: in, required, type=byte
       A three-element byte array containing the color
       triple. The triple can be either a row or column
       vector of three elements or it can be an N-by-3 array of
       color triples.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgcolor.pro)

CGCOLOR[3]

 The purpose of this function is to obtain drawing colors
 by name and in a device/decomposition independent way.
 
 :Returns:
     The return value depends on the color mode in effect at the time
     the program is called and which keyword is used with the program.
     In normal operation, if the graphics device is using indexed color
     mode, the program will load a color at a unique (or specified)
     index and return that index number. If the graphics device is using
     decomposed color mode, the program will create a 24-bit color value
     that can be used to specify the particular color desired. In this
     case, no color is loaded in the color table. This is the preferred
     mode for working with colors in IDL.
     
 :Params:
    theColour: required, optional, type=varies
        Normally the name of the color desired. However, this can also be
        a string index number (e.g., '215') or a byte or short integer
        value (e.g, 215B or 215S). If this is the case, the color
        in the current color table at this index number is used for the 
        color that is returned. The value may also be a vector of color names. 
        The color may also be a three-element byte or integer array specifying a 
        user-defined color triple. Only one color triple is allowed.

        To see a list of the color names available set the NAMES keyword. Colors available are these::

           Active            Almond     Antique White        Aquamarine             Beige            Bisque
           Black               Blue       Blue Violet             Brown         Burlywood        Cadet Blue
           Charcoal       Chartreuse         Chocolate             Coral   Cornflower Blue          Cornsilk
           Crimson              Cyan    Dark Goldenrod         Dark Gray        Dark Green        Dark Khaki
           Dark Orchid      Dark Red       Dark Salmon   Dark Slate Blue         Deep Pink       Dodger Blue
           Edge                 Face         Firebrick      Forest Green             Frame              Gold
           Goldenrod            Gray             Green      Green Yellow         Highlight          Honeydew
           Hot Pink       Indian Red             Ivory             Khaki          Lavender        Lawn Green
           Light Coral    Light Cyan        Light Gray      Light Salmon   Light Sea Green      Light Yellow
           Lime Green          Linen           Magenta            Maroon       Medium Gray     Medium Orchid
           Moccasin             Navy             Olive        Olive Drab            Orange        Orange Red
           Orchid     Pale Goldenrod        Pale Green            Papaya              Peru              Pink
           Plum          Powder Blue            Purple               Red              Rose        Rosy Brown
           Royal Blue   Saddle Brown            Salmon       Sandy Brown         Sea Green          Seashell
           Selected           Shadow            Sienna          Sky Blue        Slate Blue        Slate Gray
           Snow         Spring Green        Steel Blue               Tan              Teal              Text
           Thistle            Tomato         Turquoise            Violet        Violet Red             Wheat
           White              Yellow

        Here are the Brewer color names::

           WT1        WT2       WT3       WT4       WT5       WT6       WT7       WT8
           TAN1      TAN2      TAN3      TAN4      TAN5      TAN6      TAN7      TAN8
           BLK1      BLK2      BLK3      BLK4      BLK5      BLK6      BLK7      BLK8
           GRN1      GRN2      GRN3      GRN4      GRN5      GRN6      GRN7      GRN8
           BLU1      BLU2      BLU3      BLU4      BLU5      BLU6      BLU7      BLU8
           ORG1      ORG2      ORG3      ORG4      ORG5      ORG6      ORG7      ORG8
           RED1      RED2      RED3      RED4      RED5      RED6      RED7      RED8
           PUR1      PUR2      PUR3      PUR4      PUR5      PUR6      PUR7      PUR8
           PBG1      PBG2      PBG3      PBG4      PBG5      PBG6      PBG7      PBG8
           YGB1      YGB2      YGB3      YGB4      YGB5      YGB6      YGB7      YGB8
           RYB1      RYB2      RYB3      RYB4      RYB5      RYB6      RYB7      RYB8
           TG1        TG2       TG3       TG4       TG5       TG6       TG7       TG8
            
        The color name "OPPOSITE" is also available. It chooses a color "opposite" to the 
        color of the pixel in the upper-right corner of the display, if a window is open.
        Otherwise, this color is "black" in PostScript and "white" everywhere else.
        The color OPPOSITE is used if this parameter is absent or a color name is mis-spelled.
        
         The color name "BACKGROUND" can similarly be used to select the color of the pixel
         in the upper-right corner of the display, if a window is open.
           
    colorindex: in, optional, type=byte
        The color table index where the color should be loaded. Colors are
        loaded into the color table only if using indexed color mode in the
        current graphics device. If this parameter is missing, the color will
        be loaded at a unique color index number, if necessary.
        
 :Keywords:
     allcolors: in, optional, type=boolean, default=0
        Set this keyword to return indices, or 24-bit values, or color
        triples, for all the known colors, instead of for a single color.
     brewer: in, optional, type=boolean, default=0
        An obsolete keyword. If used, only Brewer colors are loaded into the color
        vectors internally.
     cancel: out, optional, type=boolean, default=0
        This keyword is always set to 0, unless that SELECTCOLOR keyword is used.
        Then it will correspond to the value of the CANCEL output keyword in PICKCOLORNAME.
     check_connection: in, optional, type=boolean, default=0
         An obsolete keyword now completely ignored.
     colorstructure: out, optional, type=structure
        This output keyword (if set to a named variable) will return a
        structure in which the fields will be the known color names (without spaces)
        and the values of the fields will be either color table index numbers or
        24-bit color values. If you have specified a vector of color names, then
        this will be a structure containing just those color names as fields.
     decomposed: in, optional, type=boolean
        Set this keyword to 0 or 1 to force the return value to be
        a color table index or a 24-bit color value, respectively. This
        keyword is normally set by the color state of the current graphics device.
     filename: in, optional, type=string
        The  name of an ASCII file that can be opened to read in color values and color 
        names. There should be one color per row in the file. Please be sure there are 
        no blank lines in the file. The format of each row should be::

           redValue  greenValue  blueValue  colorName

        Color values should be between 0 and 255. Any kind of white-space
        separation (blank characters, commas, or tabs) are allowed. The color
        name should be a string, but it should NOT be in quotes. A typical
        entry into the file would look like this::

           255   255   0   Yellow
     names: in, optional, type=boolian, default=0
        If this keyword is set, the return value of the function is a string array 
        containing the names of the colors. These names would be appropriate, for example, 
        in building a list widget with the names of the colors. If the NAMES
        keyword is set, the COLOR and INDEX parameters are ignored.
     ncolors: out, optional, type=integer
        Returns the number of colors that cgColor "knows" about. Currently ncolors=193.
     nodisplay: in, optional, type=boolean, default=0
        An obsolete keyword, now totally ignored.
     row: in, optional, type=boolean
        If this keyword is set, the return value of the function when the TRIPLE
        keyword is set is returned as a row vector, rather than as the default
        column vector. This is required, for example, when you are trying to
        use the return value to set the color for object graphics objects. This
        keyword is completely ignored, except when used in combination with the
        TRIPLE keyword.
     selectcolor: in, optional, type=boolean
       Set this keyword if you would like to select the color name with
       the PICKCOLORNAME program. Selecting this keyword automaticallys sets
       the INDEX positional parameter. If this keyword is used, any keywords
       appropriate for PICKCOLORNAME can also be used. If this keyword is used,
       the first positional parameter can be a color name that will appear in
       the SelectColor box.
     triple: in, optional, type=boolean
        Setting this keyword will force the return value of the function to
        always be a color triple, regardless of color decomposition state or
        visual depth of the machine. The value will be a three-element column
        vector unless the ROW keyword is also set.
     _ref_extra: in, optional
        Any keyword parameter appropriate for PICKCOLORNAME can be used.
       These include BOTTOM, COLUMNS, GROUP_LEADER, INDEX, and TITLE.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgcolor.pro)

CGCONTOUR

The purpose of cgContour is to create a wrapper for the traditional IDL graphics
command, Contour. The Contour command has a number of deficiencies that make it
difficult to use in a modern computing environment. cgContour corrects these
deficiencies and allows the user to produce traditional contour plots in a device
and machine independent manner.

The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
to be installed on your machine.

:Categories:
Graphics

:Params:
data: in, required, type=any
A one- or two-dimensional array containing the values that make
up the contour surface.
x: in, optional, type=any
A vector or two-dimensional array specifying the X coordinates for
the contour surface.
y: in, optional, type=any
A vector or two-dimensional array specifying the Y coordinates for
the contour surface.

:Keywords:
addcmd: in, optional, type=boolean, default=0
Set this keyword to add the command to an cgWindow. Setting this keyword
automatically sets the WINDOW keyword, but the command does not erase the
graphics window as it would normally.
axiscolor: in, optional, type=string/integer, default='opposite'
If this keyword is a string, the name of the axis color.
Otherwise, the keyword is assumed to be a color index into the current color table.
axescolor: in, optional, type=string/integer
Provisions for bad spellers.
background: in, optional, type=string/integer, default='background'
If this keyword is a string, the name of the background color.
Otherwise, the keyword is assumed to be a color index into the current color table.
c_colors: in, optional, type=integer/string vector
Set to the index values of the contour colors or to named colors. Must contain
the same number of colors as the number of requested contour levels.
c_labels: in, optional, type=integer
A vector that specifies which contour levels to label. If used, the LABEL
keyword is ignored.
c_charsize: in, optional, type=float
The character size of the annotations used on the contour lines themselves.
By default, 75% of `Charsize`.
cell_fill: in, optional, type=boolean, default=0
Set to indicate filled contours should be created using the "cell fill" method.
This keyword should always be set if displaying filled contours on map projections
or if missing data is present in the data you are contouring.
charsize: in, optional, type=float, default=cgDefCharSize()
The character size for axes annotations. Uses cgDefCharSize to select default
character size, unless !P.Charsize is set, in which case !P.Charsize is always used.
color: in, optional, type=string/integer, default='black'
If this keyword is a string, the name of the data color. By default, same as AXISCOLOR.
Otherwise, the keyword is assumed to be a color index into the current color table.
font: in, optional, type=integer, default=!P.Font
The type of font desired for axis annotation.
fill: in, optional, type=boolean, default=0
Set to indicate filled contours should be created.
irregular: in, optional, type=boolean
If this keyword is set, the data, x, and y input parameters are taken to be
irregularly gridded data, the the data is gridded for use in the contour plot
using the Triangulate and Trigrid method. The resolution of the gridded output
is set by the RESOLUTION keyword.
label: in, optional, type=integer, default=1
An number that tells how to label contour levels. A 0 means
no contour levels are labelled. A 1 (the default) means all contour levels are
labelled. A 2 means label every 2nd contour level is labelled. A 3 means every
3rd contour level is labelled, and so on.
layout: in, optional, type=intarr(3)
This keyword specifies a grid with a graphics window and determines where the
graphic should appear. The syntax of LAYOUT is three numbers: [ncolumns, nrows, location].
The grid is determined by the number of columns (ncolumns) by the number of
rows (nrows). The location of the graphic is determined by the third number. The
grid numbering starts in the upper left (1) and goes sequentually by column and then
by row.
levels: in, optional, type=any
A vector of data levels to contour. If used, NLEVELS is ignored. If missing,
NLEVELS is used to construct N equally-spaced contour levels.
map_object: in, optional, type=object
If you are overplotting (OVERPLOT=1) on a map projection set up with Map_Proj_Init
and using projected meter space, rather than lat/lon space, then you can use this
keyword to provide a cgMap object that will allow you to convert the `x` and `y`
grid parameters from longitude and latitude, respectively, to projected meter space
before the contour is displayed. Note, you MUST pass the `x` and `y` grid parameters
to cgContour if you are overplotting on a map projection. There is no checking to
be sure these parameters are in the correct longitude and latitude range, respectively.
missingvalue: in, optional, type=any
Use this keyword to identify any missing data in the input data values.
noclip: in, optional, type=boolean, default=0
Normally, the plot is clipped to the axes boundaries. Setting this keyword prevents
such clipping. Normally, this keyword is only used when there is a problem displaying
contour plots in 3D space.
nlevels: in, optional, type=integer, default=6
If the Contour plot LEVELS keyword is not used, this keyword will produce this
number of equally spaced contour intervals. Unlike the Contour NLEVELS keyword,
this keyword actually works!
noerase: in, optional, type=boolean, default=0
Set this keyword to prevent the window from erasing the contents before displaying
the contour plot.
olevels: out, optional
Set to a named variable to return the actual contour levels used in the program.
Unfortunately, output variables cannot be returned if the cgContour command is
being executed in a cgWindow.
onimage: in, optional, type=boolean, default=0
If this keyword is set, and an image has been display previously with cgImage,
then the contour plot will determine the location of the image in the display
window and overplot itself onto that image.
outcolor: in, optional, type=string, default='charcoal'
The color of the contour lines when the `Outline` keyword is used.
outfilename: in, optional, type=string
If the `Output` keyword is set, the user will be asked to supply an output
filename, unless this keyword is set to a non-null string. In that case, the
value of this keyword will be used as the filename and there will be no dialog
presented to the user.
outline: in, optional, type=boolean, default=0
This keyword applies only if the `Fill` keyword is set. It will draw the
contour lines on top of the filled contour. It draws the outline in the `OutColor`.
output: in, optional, type=string, default=""
Set this keyword to the type of output desired. Possible values are these::

'PS' - PostScript file
'EPS' - Encapsulated PostScript file
'PDF' - PDF file
'BMP' - BMP raster file
'GIF' - GIF raster file
'JPEG' - JPEG raster file
'PNG' - PNG raster file
'TIFF' - TIFF raster file

Or, you can simply set this keyword to the name of the output file, and the type of
file desired will be determined by the file extension. If you use this option, the
user will not be prompted to supply the name of the output file.

All raster file output is created through PostScript intermediate files (the
PostScript files will be deleted), so ImageMagick and Ghostview MUST be installed
to produce anything other than PostScript output. (See cgPS2PDF and PS_END for
details.) And also note that you should NOT use this keyword when doing multiple
plots. The keyword is to be used as a convenient way to get PostScript or raster
output for a single graphics command. Output parameters can be set with cgWindow_SetDefs.
overplot: in, optional, type=boolean, default=0
Set this keyword to overplot the contours onto a previously established
data coordinate system.
palette: in, optional, type=byte
A (256x3) color palette containing the RGB color vectors to use for coloring contours.
Contour colors will be sampled from the color table palette into the number
of contour levels required. If the palette is NOT 256 elements in length, then
it is assumed that the length corresponds to the number of levels to be contoured.
position: in, optional, type=float
Set this keyword to a four-element [x0,y0,x1,y1] array giving the contour plot
position in normalized coordinates.
resolution: in, optional, type=integer array, default=[41\,41]
If the IRREGULAR keyword is set, this keyword specifies the X and Y resolution
in a two element integer array of the final gridded data that is sent to the
contour plot.
t3d: in, optional, type=boolean, default=0
Set this keyword to use the 3D axis rotation matrix in !P.T3D.
traditional: in, optional, type=boolean, default=0
If this keyword is set, the traditional color scheme of a black background for
graphics windows on the display is used and PostScript files always use a white background.
window: in, optional, type=boolean, default=0
Set this keyword if you want to display the plot in a resizable graphics window.
xstyle: in, optional, type=integer, default=1
If unused in the program, set to 1 to force exact axis scaling.
xthick: in, optional, type=integer, default=1
The thickness of the X axis annotations.
xticklen: in, optional, type=float, default=0.025
The length of the X tick marks. Set to a negative value to create outward
facing tick marks.
xticks: in, optional, type=integer
The number of tick intervals on the X axis.
xtickv: in, optional, type=string
A vector of tick values to use with the tick marks. See IDL documentation for
graphics keywords for additional information.
ystyle: in, optional, type=integer, default=1
If unused in the program, set to 1 to force exact axis scaling.
ythick: in, optional, type=integer, default=1
The thickness of the Y axis annotations.
yticklen: in, optional, type=float, default=0.025
The length of the Y tick marks. Set to a negative value to create outward
facing tick marks.
yticks: in, optional, type=integer
The number of tick intervals on the Y axis.
ytickv: in, optional, type=string
A vector of tick values to use with the tick marks. See IDL documentation for
graphics keywords for additional information.
_ref_extra: in, optional, type=any
Any keyword appropriate for the IDL Contour command is allowed in the program.

:Examples:
Use as you would use the IDL CONTOUR command::
data = dist(51)
cgContour, data
LoadCT, 33
cgContour, data, /FILL
cgContour, data, /OVERPLOT

If you wish to overplot on top of an image, use the ONIMAGE keyword, rather
than the OVERPLOT keyword:
cgImage, data, /SCALE, XRANGE=[-10, 10], YRANGE=[-5,5], /AXES
cgContour, data, /ONIMAGE

See `Device Independent Contour Plots <http://www.idlcoyote.com/graphics_tips/cgcontour.html>'
for additional examples.

:History:
Change History::
Written, 11 November 2010. DWF.
Restored the CELL_FILL keyword, which had been accidentally removed in
the earlier version. 12 November 2010. DWF.
Add the ability to specify the contour colors as color names. 16 November 2010. DWF.
Now setting decomposition state by calling SetDecomposedState. 16 November 2010. DWF.
Final color table restoration skipped in Z-graphics buffer. 17 November 2010. DWF.
Background keyword now applies in PostScript file as well. 17 November 2010. DWF.
Many changes after BACKGROUND changes to get !P.MULTI working again! 18 November 2010. DWF.
Fixed a small problem with the OVERPLOT keyword. 18 Nov 2010. DWF.
Changes so that color variables don't change type. 23 Nov 2010. DWF.
Added WINDOW keyword to allow graphic to be displayed in a resizable graphics window. 8 Dec 2010. DWF
Modifications to allow cgContour to be drop-in replacement for old Contour commands in
indexed color mode. 24 Dec 2010. DWF.
Previous changes introduced problems with OVERPLOT that have now been fixed. 28 Dec 2010. DWF.
Set NOERASE keyword from !P.NoErase system variable when appropriate. 28 Dec 2010. DWF.
Additional problems with NOERASE discovered and solved. 29 Dec 2010. DWF.
Change to DECOMPOSED color was using incorrect color tables. 29 Dec 2010. DWF.
In some cases, I was turning BYTE values to strings without converting to
INTEGERS first. 30 Dec 2010. DWF.
Still working on getting contour colors to work in decomposed color mode in all
circumstances. 2 Jan 2011. DWF.
Fixed problem with FILL when no contour colors (C_COLORS) are specified. 3 Jan 2011. DWF.
Fixed a problem that preventing output keyword (e.g., PATH_INFO) from being returned properly.
3 Jan 2011. DWF.
Fixed a problem calculating NLEVELS when LEVELS keyword was used instead. 3 Jan 2011. DWF.
TVLCT commands protected from NULL device. 4 Jan 2011. DWF.
Fixed a no color problem when CELL_FILL was set. 11 Jan 2011. DWF.
Fixed a problem with overlaying filled contours with /OVERPLOT. 11 Jan 2011. DWF.
Selecting character size now with cgDefCharSize. 11 Jan 2011. DWF.
Moved setting to decomposed color before color selection process to avoid PostScript
background problems when passed 24-bit color integers. 12 Jan 2011. DWF.
Fixed a problem in which I assumed the background color was a string. 18 Jan 2011. DWF.
Added ADDCMD keyword. 26 Jan 2011. DWF.
Added LAYOUT keyword. 28 Jan 2011. DWF.
Added PALETTE keyword. 4 Feb 2011. DWF.
Color table vectors must be obtained AFTER loading the color palette. 6 March 2011. DWF.
Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF
Modifications to allow palettes of less than 256 elememts in length to be used. 1 April 2011. DWF.
Modifications to repair axes and tickmarks when creating filled contour plots. 28 May 2011. DWF.
Whoops! Last fix shouldn't apply to OVERPLOTTING. Fixed. 22 June 2011. DWF.
Still more work to get axes overplotting to work correct. 5 July 2011. DWF.
Added an ONIMAGE keyword that allows the contours to be overplotted on top of an image that
has been displayed with cgImage. This requires that the SAVE keyword is set in the
cgImage call.
Improved error handling. 26 Aug 2011. DWF.
Got the data type correct in the part of the code that creates levels. 6 Sept 2011. DWF.
Small change to allow cgWindow to set the current graphics window if it is the only
window on the display. 15 Sept 2011. DWF.
Had to add XTICKV, YTICKV, XTICKS, and YTICKS keywords to get repaired axes to work
properly on filled contour plots. There may be other keywords needed, but I am
going to add them on an as-needed basis. 30 Sept 2011. DWF.
Other keywords WERE needed! I added XTICKLEN and YTICKLEN keywords to the repaired axes
code. 3 Oct 2011. DWF.
Change from 15 Sept 2011 forgot to include the possibility of pixmap windows. Algorithm
made more robust. 27 Oct 2011. DWF.
There was a problem with axes when plotting contours in 3D that has been fixed. 18 Nov 2011. DWF.
Added OLEVELS keyword. 7 Dec 2011. DWF.
Added OUTLINE and OUTCOLOR keywords. 8 Dec 2011. DWF.
Modified the way the axes are drawn when given a negative tick length. 9 Dec 2011. DWF.
Added the ability to send the output directly to a file via the OUTPUT keyword. 9 Dec 2011, DWF.
PostScript, PDF, and Imagemagick parameters can now be tailored with cgWindow_SetDefs. 14 Dec 2001. DWF.
Made sure the OUTLINE keyword works with CELL_FILL, too. 16 Dec 2011. DWF.
Modified to use cgDefaultColor for default color selection. 24 Dec 2011. DWF.
Added MAP_OBJECT keyword. 28 Dec 2011. DWF.
Changes to allow better default colors, based on changes to cgColor and cgDefaultColor. 1 Feb 2012. DWF.
Axis repair for filled contour plots (done with AXIS) results in incorrect tick labeling with
date/time axes. Replaced repair code with actual Contour command. 9 March 2012. DWF.
Fixed a problem with color palettes by defining NLEVELS according to the number of colors
in the palette. 19 March 2012. DWF.
Now allowing the user to draw in the "background" color, if the COLOR or AXISCOLOR is "BACKGROUND". 19 March 2012. DWF.
The axis repair change on 9 March was not working in multi plots because the plot was already
advanced. Added a fix to make sure the repair is to the correct multi plot. 20 April 2012. DWF.

:Copyright:
Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgcontour.pro)

CGCONTROL

Allows the user to set various properties of an cgWindow object. This is essentially
a wrapper to the cgWindow SetProperty method.

:Categories:
Graphics

:Params:
selection: in, required, type=varies
Normally, a window index number of an cgWindow application. But, the selection
can be a widget identifier, an object reference, or a window title, depending on
which keywords are set. The cgWindow matching the selection has its properties set.

:Keywords:
all: in, optional, type=boolean
This keyword applies only to keywords that manipulate commands in the command
list (e.g., DeleteCmd). It will select all the commands in the command list to
apply the action to.
adjustsize: in, optional, type=boolean
Set this keyword to adjust default character size to the display window size.
aspect: in, optional, type=boolean
Set this keyword to the desired aspect ratio (ysize/xsize) of the window.
background: in, optional, type=string
The background color of the window. Only use if the ERASEIT property is also set.
cmdindex: in, optional, type=integer
This keyword applies only to keywords that manipulate commands in the command
list (e.g., DeleteCmd). It specifies the command index number of the command
for which the action is desired.
create_bmp: in, optional, type='string', default='cgwindow.bmp'
Set this keyword to the name of a bitmap file to create automatically from the window.
Using this keyword is a way to create a bitmap file programmatically from a cgWindow application.
The raster file will be created via ImageMagick if im_raster has been set (default).
Depreciated now in favor of the `Output` keyword.
create_gif: in, optional, type='string', default='cgwindow.gif'
Set this keyword to the name of a GIF file to create automatically from the window.
Using this keyword is a way to create a GIF file programmatically from a cgWindow application.
The raster file will be created via ImageMagick if im_raster has been set (default).
Depreciated now in favor of the `Output` keyword.
create_jpeg: in, optional, type='string', default='cgwindow.jpeg'
Set this keyword to the name of a JPEG file to create automatically from the window.
Using this keyword is a way to create a JPEG file programmatically from a cgWindow application.
The raster file will be created via ImageMagick if im_raster has been set (default).
Depreciated now in favor of the `Output` keyword.
create_pdf: in, optional, type='string', default='cgwindow.pdf'
Set this keyword to the name of a PNG file to create automatically from the window.
Using this keyword is a way to create a PDF file programmatically from a cgWindow application.
The PDF file will be created via the Coyote Graphics program cgPS2PDF.
Depreciated now in favor of the `Output` keyword.
create_png: in, optional, type='string', default='cgwindow.png'
Set this keyword to the name of a PNG file to create automatically from the window.
Using this keyword is a way to create a PNG file programmatically from a cgWindow application.
The raster file will be created via ImageMagick if im_raster has been set (default).
create_ps: in, optional, type='string', default='cgwindow.ps'
Set this keyword to the name of a PostScript file to create automatically from the window.
Using this keyword is a way to create a PostScript file programmatically from a cgWindow application.
Depreciated now in favor of the `Output` keyword.
create_tiff: in, optional, type='string', default='cgwindow.tiff'
Set this keyword to the name of a TIFF file to create automatically from the window.
Using this keyword is a way to create a TIFF file programmatically from a cgWindow application.
The raster file will be created via ImageMagick if im_raster has been set (default).
Depreciated now in favor of the `Output` keyword.
delay: in, optional, type=float
Set this keyword to the amount of "delay" you want between commands in the command list.
deletecmd: in, optional, type=boolean
Set this keyword to delete a command in the cgWindow. The keywords cmdIndex and All
are used in deleting the specified command.
destroy: in, optional, type=boolean
Set this keyword to destroy the cgWindow program. This keyword should not be used
with other keywords.
dimensions: in, optional, type=intarr(2)
Set this keyword to a two-element array giving the xsize and ysize
of the draw widget.
eraseit: in, optional, type=boolean
If this property is set, the cgWindow erases with the background color before
displaying the commands in the window's command list.
execute: in, optional, type=boolean
Set this keyword to 1 to exectute the commands in the window's command list.
Set this keyword to 0 to prevent command excution. This is useful, for example,
if you want to load commands without having them be executed immediately.
get_keycmdindex: in, optional, type=integer
Set this value to the number of the command (zero-based) for which you want to
obtain the keyword value. If not provided, the first command (command 0) is searched.
get_keyword: in, optional, type=string
The name of the keyword whose value you want to return in get_keyvalue. The name must
be spelled EXACTLY as you used the keyword, except that case does not matter. The string
is converted to UPPERCASE to locate the proper keyword. Although it was my intention to use
this to retrieve output keyword values, this is not possible using cgWindow due to the way
Call_Procedure and keyword inheritance work.
get_keyvalue: out, optional, type=any
The value of the keyword specified in get_keyword. If the keyword cannot be found, this
value will be undefined. You MUST check for this before using the return variable in your program.
im_transparent: in, optional, type=boolean, default=0
Set this keyword to allow ImageMagick to create transparent backgrounds when it
makes raster image files from PostScript output.
im_density: in, optional, type=integer, default=300
Set this keyword to the sampling density when ImageMagick creates raster image
file from PostScript outout.
im_options: in, optional, type=string, default=""
Set this keyword to any ImageMagick options you would like to pass along to the
ImageMagick convert command when creating raster image files from PostScript output.
im_resize: in, optional, type=integer, default=25
Set this keyword to percentage that the raster image file created my ImageMagick
from PostScript output should be resized.
im_raster: in, optional, type=boolean, default=1
Set this keyword to zero to create raster files using the create_png etc. keywords
directly, instead of via ImageMagick.
im_width: in, optional, type=integer
Set this keyword to the width of the output raster file in pixel units. The height of the raster
file is set to preserve the aspect ratio of the output image. Applies only to raster images (eg
PNG, JPEG, TIFF, etc.) created from PostScript files with ImageMagick.
multi: in, optional, type=Intarr(5)
Set this keyword to the !P.MULTI setting you want to use for the window.
!P.MULTI is set to this setting before command execution, and set back to
it's default value when the commands are finished executing.
object: in, optional, type=boolean
If this keyword is set, the selection is assumed to be an object reference.
output: in, optional, type=string
This keyword should be set to the name of an output file. It is a short-hand way of
specifying the CREATE_*** keywords. The type of file is taken from the file name
extension.
palette: in, optional, type=byte
Use this keyword to pass in an N-by-3 (or 3-by-N) byte array containing the
R, G, and B vectors of a color table. It is probably easier to use cgLoadCT or
XCOLORS to load color tables for the window, but this is provided as another option.
pdf_path: out, optional, type=string
Set this keyword to the name of the path to the Ghostscript command for converting PS to PDF.
pdf_unix_convert_cmd: out, optional, type=string
Set this keyword to the name of an alternative UNIX command to convert PostScript to PDF.
ps_charsize: in, optional, type=float
The PostScript character size.
ps_decomposed: in, optional, type=boolean, default=0
Set this keyword to zero to set the PostScript color mode to indexed color and to
one to set the PostScript color mode to decomposed color.
ps_delete: in, optional, type=boolean, default=1
Set this keyword to zero if you want to keep the PostScript output ImageMagick creates
when making raster file output.
ps_encapsulated: in, optional, type=boolean, default=0
Set this keyword to configure PSCONFIG to produce encapsulated PostScript output by default.
ps_font: in, optional, type=integer
Set this keyword to the type of font you want to use in PostScript output. It sets the
FONT keyword on the PSConfig command. Normally, 0 (hardware fonts) or 1 (true-type fonts).
ps_metric: in, optional, type=boolean, default=0
Set this keyword to configure PSCONFIG to use metric values and A4 page size in its interface.
ps_quiet: in, optional, type=boolean, default=0
Set this keyword to set the QUIET keyword on PS_Start.
ps_scale_factor: in, optional, type=float
Set his keyword to the PostScript scale factor you wish to use in creating PostScript output.
ps_tt_font: in, optional, type=string
Set this keyword to the name of a true-type font to use in creating PostScript output.
restore_visualization: in, optional, type=string
Set this keyword to the name of a visualization save file to restore.
save_visualization: in, optional, type=string, default='graphic.cgs'
Set this keyword to the name of a file where the visualization should be saved.
title: in, optional, type=boolean
If this keyword is set, the selection is assumed to be a window title. All
matching is done in uppercase characters.
update: in, optional, type=boolean, default=1
Set this keyword to zero if you do not want the updates to be done immediately
after the properties are changed.
widgetid: in, optional, type=boolean
If this keyword is set, the selection is assumed to be a widget identifier.
xomargin: in, optional, type=intarr(2)
Sets the !X.OMargin system variable when multiple plots are displayed in the window.
yomargin: in, optional, type=intarr(2)
Sets the !Y.OMargin system variable when multiple plots are displayed in the window.

:Examples:
Used to set cgWindow properties::
IDL> cgControl, Background='gray', EraseIt=1
IDL> cgControl, Multi=[0,2,2]

:History:
Change History::
Written, 28 January 2011. DWF.
Added CREATE_PS keyword. 16 Feb 2011. DWF.
Added PS_QUIET, GET_KEYCMDINDEX, GET_KEYWORD, and GET_KEYVALUE keywords. 17 Feb 2011. DWF.
Added im_raster and the create_... raster options. 18 Feb 2011. Jeremy Bailin
Added the ability to set and unset adjustable text size in
cgWindow with ADJUSTSIZE keyword. 24 April 2011. DWF.
Added the ability to set the dimensions of the draw widget programmatically. 14 June 2011.
Added PS_DECOMPOSED keyword to set the PostScript color mode. 30 Aug 2011. DWF.
Added SAVE_VISUALIZATION and RESTORE_VISUALIZATION keywords. 15 Sept 2011. DWF.
Added ASPECT keyword to control window aspect ratio. 9 Nov 2011. DWF.
Added CREATE_PDF, PDF_UNIX_CONVERT_CMD, and PDF_PATH keywords. 11 Dec 2011. DWF.
Added IM_WIDTH keyword. 3 April 2012. DWF.
Added the OUTPUT keyword. 3 April 2012. DWF.

:Copyright:
Copyright (c) 2011-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgcontrol.pro)

CGDEFAULTCOLOR

The purpose of this function is to choose a default color for Coyote Graphics routines.

:Categories:
Graphics

:Returns:
Returns a scalar or vector (depends on the type of the input color) of color
names (strings) to be used as the "color" in Coyote Graphics routines. If the
MODE is 1 and the inputColor is of type LONG, then the return value is an array
or scalar of type LONG.

:Params:
inputcolour: in, optional
The input color. May be undefined, a byte, integer, long, or string. If the
device is in indexed color mode at the time the request is made, then all,
byte, integer, and long values will be treated as indices into the current
color table. The variable may be a vector.

:Keywords:
background: in, optional, type=boolean
If this keyword is set, the color is treated as a background color. Otherwise,
it is treated as a drawing color.
default: in, optional
A color of any type allowed as the `inputColour`. Used if the `inputColour` is undefined.
mode: in, optional, type=boolean
The color mode. A 0 mean indexed color mode. A 1 means decomposed color mode.
If not supplied in the call, the color mode is determined at run-time with `GetDecomposedState`.
The color mode is *always* determined at run time if the current graphics device
is the PostScript device.
traditional: in, optional, type=boolean, default=0
Set this keyword if you are using the traditional color scheme of white foreground
and black background. If this keyword is set, and the current graphics device is
the PostScript device, the colors will be reversed, in the traditional IDL graphics
way.

:Examples:
Use as a device independent way to get a color::
background = cgDefaultColor(bColor, /Background)
color = cgDefaultColor(bColor)
cgPlot, cgDemoData, Background=background, Color=color

:History:
Change History::
Written, 24 December 2011. David W. Fanning.
Modified to make sure a LONG integer in indexed color mode is in the range 0-255. 10 Jan 2012. DWF.
Modified to make sure MODE is always determined at run-time for PostScript device. 14 Jan 2012. DWF.
Allow other data types to be treated as color table index numbers, as long as they are in the
range 0 to 255, and the MODE indicates indexed color. 7 March 2012. DWF.
Modified so that the variable MODE will not change in the calling program program. 8 March 2012. DWF.

:Copyright:
Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgdefaultcolor.pro)

CGDEFCHARSIZE

   Defines a default character size for Coyote Graphics routines (cgPlot, cgContour, etc.)
   IF !P.Charsize is set, the function simply returns !P.Charsize.

 :Categories:
    Graphics, Utilities
    
 :Keywords:
     adjustsize: in, optional, type=boolean, default=0
        If this keyword is set, the output character size is adjusted to
        fit the size of the output graphics window. No adjustment is ever
        done in PostScript. Applies only when !P.Charsize=0.
     font: in, optional, type=integer, default=!P.Font
        The font type: -1 = Hershey, 0 = hardware, 1 = true-type. 
          
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 11 January 2011. DWF.      
        Added an ADJUSTSIZE keyword to allow adjustable sizing of characters
           in resizeable graphics windows. 24 April 2011. DWF.  
        Made sure this program only adjusts text size on devices that support 
           windows. 20 July 2011. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgdefcharsize.pro)

CGDISPLAY

The purpose of cgDisplay is to open a graphics window on the display, or in the
PostScript device, or in the Z-graphics buffer, depending upon the current graphics
device. In PostScript a window of the proper aspect ratio is created with PSWindow.
Using cgDisplay to open "windows" will allow you to more easily write device-independent
IDL programs.

:Categories:
Graphics

:Params:
pxsize: in, optional, type=integer, default=640
The X size of the graphics window created. By default, 640.
pysize: in, optional, type=integer, default=512
The Y size of the graphics window created. By default, 512.

:Keywords:
aspect, in, optional, type=float
Set this keyword to create a window with this aspect ratio (ysize/xsize).
If aspect is greater than 1, then the ysize will be used in the aspect
ratio calculation. If the aspect is less than or equal to 1, then the
xsize will be used in the aspect ratio calculation of the final window size.
If the input to the ASPECT keyword is an image, then the aspect ratio will
be calculated from the image itself.
color: in, optional, type=string/integer, default='white'
If this keyword is a string, the name of the data color. By default, 'white'.
Color names are those used with cgColor. Otherwise, the keyword is assumed
to be a color index into the current color table. The color is not used if
the "window" is opened in PostScript on the Z-graphics buffer.
force: in, optional, type=boolean, default=0
Because of the way cgDisplay is designed to work in many devices and in resizeable
graphics windows, it is sometimes the case that it won't create a window for you.
If you set this keyword, a graphics window will be created while in any device that
supports graphics windows.
free: in, optional, type=boolean, default=0
Set this keyword to open a window with a free or unused window index number.
This keyword applied only to graphics windows created on the computer display.
match: in, optional, type=boolean, default=0
If this keyword is set, the new display window will match the size of the current
display window, if there is one.
wid: in, optional, type=integer, default=0
The window index number of the IDL graphics window to create.
window: in, optional, type=integer, default=0
Because I want to use cgDisplay everywhere, including in resizeable graphics
windows, and I don't want it opening windows then, it first checks to be sure
there are no resizeable graphics windows on the display before it creates a window.
Setting this keyword will overrule this check and create a normal IDL graphics window
on the display. This will allow you to open a normal graphics window at the same
time a resizeable graphics window exists on the display.
xsize: in, optional, type=integer, default=640
The X size of the graphics window created. By default, 640. The PXSIZE parameter
is used in preference to the XSIZE keyword value.
ysize: in, optional, type=integer, default=512
The Y size of the graphics window created. By default, 512. The PYSIZE parameter
is used in preference to the YSIZE keyword value.
_extra: in, optional, type=any
Any keywords supported by the WINDOW command are allowed.

:Examples:
Use like the IDL WINDOW command::
IDL> cgDisplay, XSIZE=500 YSIZE=400
IDL> cgDisplay, 500, 500, WID=1, COLOR='gray'

:History:
Change History::
Written, 15 November 2010. DWF.
Changes so that color variables don't change type. 23 Nov 2010. DWF.
Moved the window index argument to the WID keyword. 9 Dec 2010. DWF.
Modified to produce a window in PostScript and the Z-buffer, too. 15 Dec 2010. DWF.
Added the FREE keyword. 3 January 2011. DWF.
I made a change that allows you to call cgDisplay inside a program that is
going to be added to a cgWindow. The program will not open a graphics window
if the current graphics window ID is found in a list of cgWindow window IDs.
It is now possible to use cgDisplay in any graphics program, even those that
will be run in cgWindow. 17 Nov 2011. DWF.
Added ASPECT keyword. 18 Nov 2011. DWF.
Allowed the window ASPECT to be set with an image argument. 25 Nov 2011. DWF.
Now use Scope_Level to always create a display when cgDisplay is called from
the main IDL level. 7 Feb 2012. DWF.
Added FORCE and MATCH keywords. 16 Feb 2012. DWF.

:Copyright:
Copyright (c) 2010-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgdisplay.pro)

CGERASE

   Provides a device-independent and color-model-independent way to erase a graphics
   window with a particular color.

 :Categories:
    Graphics
    
 :Params:
    background_color: in, optional, type=string/integer/long, default='white'
         The color to use in erasing the graphics window. Default is "white."
         Color names are those used with cgColor.
       
 :Keywords:
     color: in, optional, type=string/integer/long, default='white'
         An alternative way to specify the color to use in erasing the graphics window.
         Color names are those used with cgColor. This parameter is used in
         preference to the background_color parameter.
     layout: in, optional, type=intarr(3)
         This keyword specifies a grid with a graphics window and determines where the
         graphic should appear. The syntax of LAYOUT is three numbers: [ncolumns, nrows, location].
         The grid is determined by the number of columns (ncolumns) by the number of 
         rows (nrows). The location of the graphic is determined by the third number. The
         grid numbering starts in the upper left (1) and goes sequentually by column and then
         by row. If this keyword is used, only this portion of the window is erased.
     window: in, optional, type=boolean, default=0
         Set this keyword to erase the current cgWindow application. "Erasing" in
         this case means removing all the current commands.
          
 :Examples:
    Used to "erase" various things::
       IDL> cgErase
       IDL> cgErase, 'gray'
       IDL> cgErase, COLOR='charcoal'
       
       IDL> cgPlot, cgDemoData(1), /Window
       IDL> cgErase, /Window
       
       IDL> cgPlot, cgDemoData(17), Layout=[2,2,1]
       IDL> cgPlot, cgDemoData(17), Layout=[2,2,4]
       IDL> cgErase, Layout=[2,2,1]
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 12 November 2010. DWF.
        Modified so that input variables are not changed. 18 Nov 2010. DWF.
        Got my color selection algorithm right. COLOR keyword takes precedence
          over the parameter. 18 Nov 2010. DWF.
        Modified to erase in decomposed color, if possible.
        In some cases, I was turning BYTE values to strings without converting to 
            INTEGERS first. 30 Dec 2010. DWF.   
        Added WINDOW keyword. 26 Jan 2011. DWF. 
        Added LAYOUT keyword. 1 Feb 2011. DWF.    
        Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF

 :Copyright:
     Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgerase.pro)

CGPICKFILE

   This is a utility program for selecting data files. It is a wrapper for DIALOG_PICKFILE, 
   with the additional functionality of being able to "remember" the name and directory of 
   the last file selected by the program. It basically allows you to start the next file 
   selection from the location of the previous file selection.

 :Categories:
    Utility
    
 :Returns:
    The fully-qualified name of the selected file or a null string if the CANCEL 
    button was selected.
    
 :Keywords:
     datadir: in, optional, type=string
         Set this keyword to the name of the data directory. If not set, the program 
         assumes the data directory is rooted in the directory that holds this program 
         file, or the directory directly above it. If it can't find a "data" directory 
         in either of these two locations, the current directory is used as the "data" 
         directory. The data directory is ONLY used if there is no "current" last 
         directory. In other words, it is only used if cgPickfile has not been called 
         in the current IDL session.
     demo: in, optional, type=boolean, default=0 
         If set, starts in the !DIR/examples/data directory.
     jpeg: in, optional, type=boolean, default=0  
         If set, starts in the "jpeg" directory. It assumes the jpeg directory is rooted 
         in the "data" directory.
     hdf: in, optional, type=boolean, default=0 
         If set, starts in the "hdf" directory. It assumes the hdf directory is rooted 
         in the "data" directory.
     last_file: in, optional, type=boolean, default=0  
         If set, the name of the last file opened is placed in the filename widget.
     lidar: in, optional, type=boolean, default=0 
         If set, starts in the "lidar" directory. It assumes the lidar directory is 
         rooted in the "data" directory.
     ncdf: in, optional, type=boolean, default=0 
         If set, starts in the "ncdf" directory. It assumes the ncdf directory is 
         rooted in the "data" directory.
     png: in, optional, type=boolean, default=0 
         If set, starts in the "png" directory. It assumes the png directory is 
         rooted in the "data" directory.
     tiff: in, optional, type=boolean, default=0 
         If set, starts in the "tiff" directory. It assumes the tiff directory is 
         rooted in the "data" directory.
     title: in, optional, type=string, default="Please Select a File"
         The title for the selection dialog window. If the `Write` keyword is set,
         the default title becomes "Please Select a File for Writing".
    write: in, optional, type=boolean, default=0
         Set this keyword to change the default title to "Please Select a File for Writing".
     _ref_extra: in, optional
          Accepts any input keywords to DIALOG_PICKFILE (e.g., FILTER).
          
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Adapted from FSC_PICKFILE to be a Coyote Graphics routine by David W. Fanning, 4 Aug 2011.
        Added keywords TITLE and WRITE to work around a bug in Dialog_Pickfile that clips the
           input filenames. 25 Feb 2012. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgpickfile.pro)

CGPLOT

The purpose of cgPlot is to create a wrapper for the traditional IDL graphics
command, Plot. The primary purpose of this is to create plot commands that work
and look identically both on the display and in PostScript files.

Program default colors will depend on the IDL graphics window. If no windows are currently
open when the program is called, cgDisplay is used to create a window.

The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
to be installed on your machine.

:Categories:
Graphics

:Params:
x: in, required, type=any
If X is provided without Y, a vector representing the dependent values to be
plotted If both X and Y are provided, X is the independent parameter and
Y is the dependent parameter to be plotted.
y: in, optional, type=any
A vector representing the dependent values to be plotted.

:Keywords:
addcmd: in, optional, type=boolean, default=0
Set this keyword to add the command to the resizeable graphics window cgWindow.
aspect: in, optional, type=float, default=none
Set this keyword to a floating point ratio that represents the aspect ratio
(ysize/xsize) of the resulting plot. The plot position may change as a result
of setting this keyword. Note that `Aspect` cannot be used when plotting with
!P.MULTI.
axiscolor: in, optional, type=string/integer, default='opposite'
If this keyword is a string, the name of the axis color.
Otherwise, the keyword is assumed to be a color index into the current color table.
axescolor: in, optional, type=string/integer
Provisions for bad spellers.
background: in, optional, type=string/integer, default='background'
If this keyword is a string, the name of the background color.
Otherwise, the keyword is assumed to be a color index into the current color table.
charsize: in, optional, type=float, default=cgDefCharSize()
The character size for axes annotations. Uses cgDefCharSize to select default
character size, unless !P.Charsize is set, in which case !P.Charsize is always used.
color: in, optional, type=string/integer, default='black'
If this keyword is a string, the name of the data color. By default, 'black'.
Color names are those used with cgColor. Otherwise, the keyword is assumed
to be a color index into the current color table.
font: in, optional, type=integer, default=!P.Font
The type of font desired for axis annotation.
isotropic: in, optional, type=boolean, default=0
A short-hand way of setting the `Aspect` keyword to 1.
layout: in, optional, type=intarr(3)
This keyword specifies a grid with a graphics window and determines where the
graphic should appear. The syntax of LAYOUT is three numbers: [ncolumns, nrows, location].
The grid is determined by the number of columns (ncolumns) by the number of
rows (nrows). The location of the graphic is determined by the third number. The
grid numbering starts in the upper left (1) and goes sequentually by column and then
by row.
nodata: in, optional, type=boolean, default=0
Set this keyword to draw axes, but no data.
noerase: in, optional, type=boolean, default=0
Set this keyword to draw the plot without erasing the display first.
outfilename: in, optional, type=string
If the `Output` keyword is set, the user will be asked to supply an output
filename, unless this keyword is set to a non-null string. In that case, the
value of this keyword will be used as the filename and there will be no dialog
presented to the user.
output: in, optional, type=string, default=""
Set this keyword to the type of output desired. Possible values are these::

:Examples:
Use as you would use the IDL PLOT command::
cgPlot, Findgen(11)
cgPlot, Findgen(11), Aspect=1.0
cgPlot, Findgen(11), Color='olive', AxisColor='red', Thick=2
cgPlot, Findgen(11), Color='blue', SymColor='red', PSym=-16

:History:
Change History::
Written, 12 November 2010. DWF.
Added SYMCOLOR keyword, and allow all 46 symbols from SYMCAT. 15 November 2010. DWF.
Added NODATA keyword. 15 November 2010. DWF.
Now setting decomposition state by calling SetDecomposedState. 16 November 2010. DWF.
Final color table restoration skipped in Z-graphics buffer. 17 November 2010. DWF.
Fixed a problem with overplotting with symbols. 17 November 2010. DWF.
Background keyword now applies in PostScript file as well. 17 November 2010. DWF.
Many changes after BACKGROUND changes to get !P.MULTI working again! 18 November 2010. DWF.
Fixed a small problem with the OVERPLOT keyword. 18 Nov 2010. DWF.
Changes so that color inputs don't change type. 23 Nov 2010. DWF.
Added WINDOW keyword to allow graphic to be displayed in a resizable graphics window. 8 Dec 2010. DWF
Modifications to allow cgPlot to be drop-in replacement for old PLOT commands in
indexed color mode. 24 Dec 2010. DWF.
Previous changes introduced problems with OVERPLOT that have now been fixed. 28 Dec 2010. DWF.
Set NOERASE keyword from !P.NoErase system variable when appropriate. 28 Dec 2010. DWF.
Additional problems with NOERASE discovered and solved. 29 Dec 2010. DWF.
In some cases, I was turning BYTE values to strings without converting to
INTEGERS first. 30 Dec 2010. DWF.
Selecting character size now with cgDefCharSize. 11 Jan 2011. DWF.
Moved setting to decomposed color before color selection process to avoid PostScript
background problems when passed 24-bit color integers. 12 Jan 2011. DWF.
Changed _EXTRA to _REF_EXTRA on procedure definition statement to be able to return
plot keywords such as XGET_TICKS. 13 Jan 2011. DWF.
Added SYMSIZE keyword. 16 Jan 2011. DWF.
Fixed a problem in which I assumed the background color was a string. 18 Jan 2011. DWF.
Added ADDCMD keyword. 26 Jan 2011. DWF.
Added LAYOUT keyword. 28 Jan 2011. DWF.
Made a modification that allows THICK and COLOR keywords apply to symbols, too. 24 Feb 2011. DWF.
Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF
Somehow I had gotten independent and dependent data reversed in the code. Put right. 16 May 2011. DWF.
Allowed ASPECT (and /ISOTROPIC) to take into account input POSITION. 15 June 2011. Jeremy Bailin.
Updated the BACKGROUND color selection from lessons learned in 27 Oct 2011 cgContour
corrections. 27 Oct 2011. DWF.
Added the ability to send the output directly to a file via the OUTPUT keyword. 9 Dec 2011, DWF.
PostScript, PDF, and Imagemagick parameters can now be tailored with cgWindow_SetDefs. 14 Dec 2011. DWF.
Modified to use cgDefaultColor for default color selection. 24 Dec 2011. DWF.
Over-zealous use of _STRICT_EXTRA when overplotting resulted in errors. Now use _EXTRA. 1 Jan 2012. DWF.
Changes to allow better default colors, based on changes to cgColor and cgDefaultColor. 1 Feb 2012. DWF.
Now allowing the user to draw in the "background" color, if the COLOR or AXISCOLOR is "BACKGROUND". 19 March 2012. DWF.
Scalar input parameters are changed to 1-element vectors to avoid annoying error messages from PLOT. 6 April 2012. DWF.

:Copyright:
Copyright (c) 2010-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgplot.pro)

CGPLOTS

The purpose of cgPlotS is to create a wrapper for the traditional IDL graphics
command, PlotS. The primary purpose of this is to create plot commands that work
and look identically both on the display and in PostScript files.

The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
to be installed on your machine.

:Categories:
Graphics

:Params:
X: in, required, type=any
A vector or scalar argument providing the X components of the points to be
drawn or connected. May be a 2xN or 3xN array, if Y and Z parameters are
not used.
Y: in, optional, type=any
A vector or scalar argument providing the Y components of the points to be
drawn or connected.
Z: in, optional, type=any
A vector or scalar argument providing the Z components of the points to be
drawn or connected.

:Keywords:
addcmd: in, optional, type=boolean, default=0
Set this keyword to add the command to an cgWindow display.
color: in, optional, type=string/integer, default='opposite'
If this keyword is a string, the name of the data color.
Color names are those used with cgColor. Otherwise, the keyword is assumed
to be a color index into the current color table. May be a vector of the same
length as X.
map_object: in, optional, type=object
If you are drawing on a map projection set up with Map_Proj_Init
and using projected meter space, rather than lat/lon space, then you can use this
keyword to provide a cgMap object that will allow you to convert the `x` and `y`
parameters from longitude and latitude, respectively, to projected meter space
before drawing. X and Y must both be present.
psym: in, optional, type=integer
Any normal IDL PSYM values, plus any value supported by the Coyote Library
routine SYMCAT. An integer between 0 and 46.
symcolor: in, optional, type=string/integer/vector, default=COLOR
If this keyword is a string, the name of the symbol color. By default, same as COLOR.
Otherwise, the keyword is assumed to be a color index into the current color table.
May be a vector of the same length as X.
symsize: in, optional, type=float/vector, default=1.0
A scalar or vector of symbol sizes. Default is 1.0. May be a vector of the same
length as X.
window: in, optional, type=boolean, default=0
Set this keyword to add the command to the current cgWindow application.
_extra: in, optional, type=any
Any keywords supported by the PLOTS command are allowed.

:Examples:
Use like the IDL PLOTS command::
IDL> cgPlot, Findgen(11)
IDL> cgPlotS, !X.CRange, [5,5], LINESTYLE=2, THICK=2, COLOR='red'

:History:
Change History::
Written, 12 November 2010. DWF.
Added SYMCOLOR keyword. PSYM accepts all values from SYMCAT. SYMCOLOR and SYMSIZE
keywords can be vectors the size of x. 15 November 2010. DWF
Added ability to support COLOR keyword as a vector the size of x. 15 November 2010. DWF
Now setting decomposition state by calling SetDecomposedState. 16 November 2010. DWF.
Final color table restoration skipped in Z-graphics buffer. 17 November 2010. DWF.
Changes so that color variables don't change type. 23 Nov 2010. DWF.
Modified to use decomposed color, if possible. 24 Dec 2010. DWF.
Whoops! Programming is like herding cats! 29 Dec 2010. DWF.
In some cases, I was turning BYTE values to strings without converting to
INTEGERS first. 30 Dec 2010. DWF.
Moved setting to decomposed color before color selection process to avoid PostScript
background problems when passed 24-bit color integers. 12 Jan 2011. DWF.
Added WINDOW keyword. 24 Jan 2011. DWF.
Made a modification that allows THICK and COLOR keywords apply to symbols, too. 24 Feb 2011. DWF.
Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF
Fixed a problem in which the colors of the line was not accurate in some cases. 29 November 2011. DWF.
Added the MAP_OBJECT keyword for plotting on map projections. 2 Jan 2012. DWF.

:Copyright:
Copyright (c) 2010-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgplots.pro)

CGPS2PDF

 Converts a PostScript file to a PDF file. This program requires
 the `Ghostscript <http://www.ghostscript.com/download/>` program 
 to be installed on the user's computer, unless you are using a 
 Macintosh computer or an alterntive UNIX command to do the conversion
 for you. If you are on a Macintosh, the supplied pstopdf
 program is used instead. Use the `UNIX_Convert_Cmd` keyword to select
 an alternative UNIX command (e.g., pstopdf or epstopdf).
 
 The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
 to be installed on your machine.

 :Categories:
    Utilities, Graphics
    
 :Params:
     ps_file: in, required, type=string
         The name of the input PostScript file that is being converted to a PDF file.
         If not provided, the user will be asked to select a file.
     pdf_file: in, optional, type=string
         The name of the output PDF file. If not provided, the name is constructed from
         the input PostScript file name.

 :Keywords:
     delete_ps: in, optional, type=boolean, default=0
         If this keyword is set, the PostScript file will be deleted after conversion.
     gs_path: in, optional, type=string
         This program assumes that UNIX users can access Ghostscript with the "gs"
         command. It assumes WINDOWS users have installed Ghostscript in either
         the C:\gs or C:\Program Files\gs directories. If either of these assumptions
         is incorrect, you can specify the directory where the Ghostscript executable
         resides with this keyword. (The Windows 32-bit executable is named gswin32c.exe
         and the 64-bit executable is named gswin64c.exe.)
     pagetype: in, optional, type=string, default="LETTER"
         Set this keyword to the "type" of page. Possible values are::

            "Letter" - 8.5 by 11 inches.
            "Legal" - 8.5 by 14 inches.
            "Ledger" - 11 by 17 inches.
            "A4" - 21.0 by 29.7 centimeters.
            
     showcmd: in, optional, type=boolean, default=0
          Set this keyword to print the command that is spawned in the command output window.
     silent: in, optional, type=boolean, default=0
          Set this keyword to suppress output messages.
     success: out, optional, type=boolean
          Set this keyword to a named variable that on output will contain a 1 to 
          indicate successful completion of the command, or to 0 otherwise.
     unix_convert_cmd: in, optional, type=string
          There are a number of commands on UNIX machines for converting PostScript files
          to PDF files. This program assumes you are using Ghostscript to do the conversion
          for you. The Ghostscript command on most UNIX machines is "gs", which is used if
          this keyword is undefined. However, if you would prefer to use another program to do
          the conversion for you, you can specify the name of the command here. For example,
          "pstopdf" or "epstopdf". In creating the actual command, this command will be
          separated by a space from the input file name. In other words, if the alternative
          conversion command was "pstopdf", the actual command would be "pstopdf" + " " + ps_file.
          Any output filename is ignored. This command does not apply to Macintosh or Windows 
          computers.
     version: out, optional, type=string
         On exit, contains the version of Ghostscipt that was used. Not available on Macs
         or if an alternative UNIX command was used.
          
 :Examples:
    A typical sequence of commands to create a test.pdf file::
    
       PS_Start, Filename='test.ps'
       cgHistoplot, cgDemoData(7), /Fill
       PS_End
       cgPS2PDF, 'test.ps'
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 6 December 2011, from code supplied to me by Paul Krummel. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgps2pdf.pro)

CGQUERY

   Provides information about any cgWindow applications currently on the display. Returns
   the window index numbers of any cgWindow applications current on the display.

 :Categories:
    Graphics
    
 :Keywords:
     count: out, optional, type=long
         The number of cgWindow applications currently on the display.
     current: in, optional, type=boolean
         If set, the current cgWindow application information is returned in the result
         of the function and in the information keywords.
     dimensions: out, optional, type=integer
         The dimensions of the ctWindow application, [xdim, ydim, n].
     objectref: out, optional, type=object
         A vector of FSC_CMDWINDOW object references for each cgWindow application currently 
         on the display.
     title: out, optional, type=string
         A vector of window titles for each cgWindow application currently on the display.
     widgetID: out, optional, type=long
         A vector of widget identifiers of the top-level base widget for each cgWindow
         application currently on the display.
          
 :Returns:
      windowIndexID: out, type=long
          An array of window index numbers for each cgWindow application currently on the display.
          
 :Examples:
    Used as a query routine::
       IDL> wids = cgQuery(TITLE=titles, COUNT=count)
       IDL> index = Where(StrUpCase(titles) EQ 'PLOT WINDOW', tcnt)
       IDL> IF tcnt GT 0 THEN cgSet, wids[index]
       IDL> cgWindow, 'Oplot', thisData, /AddCmd
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 23 January 2011. DWF.
        Added DIMENSIONS keyword to return current dimensions of cgWindows. 24 Feb 2011. DWF.
        Made sure this program only returns information on devices that support windows. 20 July 2011. DWF.
        
 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgquery.pro)

CGSET

   Allows the user to select the cgWindow application to be the "current" application.
   Selection can be made based on window index number, widget identifier, object reference,
   or window title.

 :Categories:
    Graphics
    
 :Params:
    selection: in, optional, type=varies
       Normally, a window index number of an cgWindow application. But, the selection
       can be a widget identifier, an object reference, or a window title, depending on
       which keywords are set. The cgWindow matching the selection is made the "current"
       cgWindow and the application is moved forward on the display.
       
 :Keywords:
     display: in, optional, type=boolean, default=0
         If this keyword is set, the selection is made the "current" application,
         and then the graphics window of the application is made the current graphics
         window. If there is no selection, then the current cgWindow graphics window
         is made the current graphics window.
     object: in, optional, type=boolean
         If this keyword is set, the selection is assumed to be an object reference.
     title: in, optional, type=boolean
         If this keyword is set, the selection is assumed to be a window title. All
         matching is done in uppercase characters.
     widgetid: in, optional, type=boolean
         If this keyword is set, the selection is assumed to be a widget identifier.
          
 :Examples:
    Used with query routine::
       IDL> wids = cgQuery(TITLE=titles, COUNT=count)
       IDL> index = Where(StrUpCase(titles) EQ 'PLOT WINDOW', tcnt)
       IDL> IF tcnt GT 0 THEN cgSet, wids[index]
       IDL> cgWindow, 'Oplot', thisData, /AddCmd
       IDL> cgSet ; Bring current window forwad on display
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 23 January 2011. DWF.
        If selection match isn't provided, as like WShow to bring the current 
           window forward on display. 26 Jan 2011. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgset.pro)

CGSHOW

   Allows the user to select the cgWindow application to be the brought forward on the display.
   Selection can be made based on window index number, widget identifier, object reference,
   or window title. This is the equivalent of WShow for normal graphics windows.

 :Categories:
    Graphics
    
 :Params:
    selection: in, required, type=varies
       Normally, a window index number of an cgWindow application. But, the selection
       can be a widget identifier, an object reference, or a window title, depending on
       which keywords are set. The cgWindow matching the selection is made the "current"
       cgWindow and the application is moved forward on the display.
       
 :Keywords:
     object: in, optional, type=boolean
         If this keyword is set, the selection is assumed to be an object reference.
     title: in, optional, type=boolean
         If this keyword is set, the selection is assumed to be a window title. All
         matching is done in uppercase characters.
     widgetid: in, optional, type=boolean
         If this keyword is set, the selection is assumed to be a widget identifier.
          
 :Examples:
    Used with query routine::
       IDL> wids = cgQuery(TITLE=titles, COUNT=count)
       IDL> index = Where(StrUpCase(titles) EQ 'PLOT WINDOW', tcnt)
       IDL> IF tcnt GT 0 THEN cgSet, wids[index]
       IDL> cgWindow, 'Oplot', thisData, /AddCmd
       IDL> cgShow ; Bring current window forwad on display
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 1 February 2011. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgshow.pro)

CGSNAPSHOT

To get accurate screen dumps with the IDL command TVRD on 24-bit
PC and Macintosh computers, you have to be sure to set color
decomposition on. This program adds that capability automatically.
In addition, the program will optionally write BMP, GIF, JPEG,
PICT, PNG, and TIFF color image files of the screen dump.

:Categories:
Graphics

:Returns:
The returned image will be a 2D image on 8-bit systems and a 24-bit pixel
interleaved true-color image on 24-bit systems. A -1 will be returned if a
file output keyword is used (e.g., JPEG, TIFF, etc.).

:Params:
xstart: in, optional, type=integer, default=0
The starting column index of the rectantular area that is to be copied.
ystart: in, optional, type=integer, default=0
The starting row index of the rectantular area that is to be copied.
ncols: in, optional, type=integer
The number of columns to read in the rectantular area that is to be
copied. By default, !D.X_Size - xstart.
nrows: in, optional, type=integer
The number of rows to read in the rectantular area that is to be
copied. By default, !D.Y_Size - ystart.

:Keywords:
bmp: in, optional, type=boolean, default=0
Set this keyword to write the screen dump as a color BMP file.
cancel: out, optional, type=boolean, default=0
An output keyword set to 1 if the user cancels out of a filename dialog.
Set to 0 otherwise.
colors: in, optional, type=integer, default=256
If a 24-bit image has to be quantized, this will set the number of colors in
the output image. Applies to BMP, GIF, PICT, and PNG formats written from
24-bit displays.(See the COLOR_QUAN documentation for details.)
cube: in, optional, type=integer
If this keyword is set to a value between 2 and 6 the color quantization will
use a cubic method of quantization. Applies to BMP, GIF, PICT, and PNG formats
written from 24-bit displays.(See the COLOR_QUAN documentation for details.)
dither: in, optional, type=boolean, default=0
If this keyword is set the quantized image will be dithered. Applies to BMP,
GIF, PICT, and PNG formats written from 24-bit displays.(See the COLOR_QUAN
documentation for details.)
filename: in, optional, type=string
The name of the output file. If you specify a name with a file extension of the
type of file you want to create (e.g., *.jpg, *.png, etc), then you do not have
to use the file type keywords (e.g., JPEG, PNG, etc.). Otherwise, you can specify
the name of the the file without an extension, use the file keywords, and a file
extension will be added to the filename automatically, depending upon the type of
output file selected.
gif: in, optional, type=boolean, default=0
Set this keyword to write the screen dump as a color GIF file.
jpeg: in, optional, type=boolean, default=0
Set this keyword to write the screen dump as a color JPEG file.
nodialog: in, optional, type=boolean, default=0
Set this keyword if you wish to avoid the DIALOG_PICKFILE dialog that asks you
to name the output file. This keyword should be set, for example, if you are
processing screens in batch mode.
order: in, optional, type=boolean, default=0
Set this keyword to determine the image order for reading the display. Corresponds to
!Order and set to such as the default.
overwrite_prompt: in, optional, type=boolean, default=0
Set this keyword if you would like to get a prompt if you are overwriting a file.
This applies only to operations involving DIALOG_PICKFILE.
pict: in, optional, type=boolean, default=0
Set this keyword to write the screen dump as a color PICT file.
png: in, optional, type=boolean, default=0
Set this keyword to write the screen dump as a color PNG file.
tiff: in, optional, type=boolean, default=0
Set this keyword to write the screen dump as a color TIFF file.
true: in, optional, type=integer, default=1
Set this keyword to the type of interleaving you want. 1 = Pixel interleaved,
2 = row interleaved, 3 = band interleaved.
type: in, optional, type=string
Set this keyword to the type of file to write. Use this instead of
setting BMP, GIF, JPEG, PICT, PNG, or TIFF keywords: TYPE='JPEG'. The
primary purpose of this is to make widget event handlers easier to write.
quality: in, optional, type=integer, default=75
This keyword sets the amount of compression for JPEG images. It should be set to a
value between 0 and 100. (See the WRITE_JPEG documentation for details.)
wid: in, optional, type=integer
The index number of the window to read from. The current graphics window
(!D.Window) is selected by default. An error is issued if no windows are
currently open on a device that supports windows.
_ref_extra: in, optional
Any keywords that are appropriate for the WRITE_*** routines are also accepted via
keyword inheritance.

:Examples:
To obtain an image of the current graphics window::

IDL> image = cgSnapshot()

To create a PNG file, named "test.png", of the current graphics window::

IDL> void = cgSnapshot(FILENAME='test.png')

To obtain the lower quadrant of a 512-by-512 graphics window as a
band interleaved image::

IDL> image = cgSnapshot(0, 0, 256, 256, TRUE=3)

:History:
Change History::
Renamed TVRead to cgSnapshot and retired TVRead. 20 February 2011. DWF.
Added the ability to get the file type from the file name extension. 26 Dec 2011. DWF.

:Copyright:
Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgsnapshot.pro)

CGTEXT

Provides a device-independent and color-model-independent way to write text into
a graphics window. It is a wrapper to the XYOUTS command.

:Categories:
Graphics

:Params:
xloc: in, required, type=depends
The X location of the text.
yloc: in, required, type=depends
The Y location of the text.
text: in, optional, type=string
The text to output. By default, the calling sequence of the program.

:Examples:
Used like the IDL XYOUTS command::
IDL> cgText, 0.5, 0.5, 'This is sample text', ALIGNMENT=0.5, /NORMAL
IDL> cgText, /PLACE, 'Use the cursor to locate this text', COLOR='dodger blue'

:History:
Change History::
Written, 19 November 2010. DWF.
Corrected a problem with setting text color and added PLACE and OUTLOC
keywords. 25 Nov 2010. DWF.
Humm, that text color problem got reset to the old way! Sheesh! Fixed. 9 Dec 2010. DWF.
Modified the way the default color is selected. Drawing with DECOMPOSED
if possible. 30 Dec 2010. DWF.
Keywords collected with _REF_EXTRA so WIDTH can be returned. Added WIDTH keyword. 6 Jan 2011. DWF.
Moved setting to decomposed color before color selection process to avoid PostScript
background problems when passed 24-bit color integers. 12 Jan 2011. DWF.
Added Window keyword. 24 Jan 2011. DWF.
Added ability to return WIDTH from resizeable graphics windows and added ADDCMD
keyword. 24 Feb 2011. DWF.
Modified error handler to restore the entry decomposition state if there is an error. 17 March 2011. DWF
Modified to allow the user to place the text in a resizeable graphics window. 13 Dec 2011. DWF.
Modified to use cgDefaultColor for default color selection. 24 Dec 2011. DWF.
Modifications to the way I obtain the WIDTH when adding the command to a cgWindow. 26 Jan 2012. DWF.

:Copyright:
Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgtext.pro)

CGWINDOW[1]

Creates a resizeable graphics window for IDL traditional commands (Plot, Contour,
Surface, etc. or for Coyote Graphics routines, `cgPlot`, `cgContour`, `cgSurf`, etc.).
In addition, the window contents can be saved as PostScript, PDF, or raster image
files. If ImageMagick is installed on your machine, the raster image files can be
created in very high quality from PostScript files.

The program is designed to work with any IDL traditional graphics routine
that is a procedure and includes no more than three positional parameters.
Any number of keywords can be used to specify properties of the graphical
output. Any number of graphics commands can be "added" the the cgWindow.
Simply use the `AddCmd` keyword to add commands.

If your program does not load its own color tables, the color tables in
effect when cgWindow is first called are used to display the graphics
commands.

To create PostScript output from within cgWindow, your graphics program
has to be written in such a way that it can work properly in the PostScript
device. This means there are no Window commands, WSet commands, and the like
that are not allowed in the PostScript device. Such commands are allowed in
programs, of course, if they are "protected". Usually such protection looks
like this::

IF (!D.Flags AND 256) NE 0 THEN Window, ...

The Coyote Graphics program `cgDisplay` is a good program for opening graphics
"windows", because such PostScript protection is built into the program. In a PostScript
device, cgDisplay produces a "window" with the same aspect ratio as the current
display graphics window, which is an aid in producing PostScript output that
looks like the same output in the display window.

Much better looking raster files can be created from the cgWindow contents,
if the raster files are created by converting PostScript files to the raster
file. If the ImageMagick "convert" command can be found on your machine, you
will have the option to create raster files using this method. I *highly*
recommend doing so, as fonts and other plot annotation will be of much higher
quality using this method.

cgWindow has been designed to work with other Coyote Graphics routines: `cgPlot`,
`cgContour`, `cgSurf`, and so on, although I expect it to work with any IDL
traditional graphics routine, if the routine is well written.

:Categories:
Graphics

:Copyright:
Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgwindow.pro)

CGWINDOW[2]

Creates a resizeable graphics window for IDL traditional commands (Plot, Contour,
Surface, etc. or for Coyote Graphics routines, cgPlot, cgContour, cgSurf, etc.).
In addition, the window contents can be saved as PostScript files or as raster image
files. If ImageMagick is installed on your machine, the raster image files can be
created in very high quality from PostScript files.

:Params:
command: in, required, type=string
The graphics procedure command to be executed. This parameter
must be a string and the the command must be a procedure. Examples
are 'Surface', 'Contour', 'Plot', 'cgPlot', cgContour, etc.
p1: in, optional, type=any
The first positional parameter appropriate for the graphics command.
p2: in, optional, type=any
The second positional parameter appropriate for the graphics command.
p3: in, optional, type=any
The third positional parameter appropriate for the graphics command.
p4: in, optional, type=any
The fourth positional parameter appropriate for the graphics command.

:Keywords:
addcmd: in, optional, type=boolean, default=0
Set this keyword to add an additional graphics command to an cgWindow.
The command is added to the last created cgWindow, unless the WinID
keyword is used to select another cgWindow. Adding a command causes
all the commands in the window to be immediately executed. If this is
not behavior you desire, use the LOADCMD keyword instead. If CMDINDEX
is used to select a command index, the new command is added before
the command currently occuping that index in the command list.
altps_Keywords: in, optional, type=string
A structure containing alternative keyword names (as tags) and values for
those keywords to be used when the current device is the PostScript device.
See http://www.idlcoyote.com/cg_tips/kwexpressions.php and the examples
below for details on how to use this keyword.
altps_Params: in, optional, type=IntArr(3)
A structure containing alternative parameter values to be used when
the current device is the PostScript device. Structure names are restricted
to the names "P1", "P2", "P3" and "P4" to correspond to the equivalent positional
parameter. See http://www.idlcoyote.com/cg_tips/kwexpressions.php and the
examples below for details on how to use this keyword.
cmddelay: in, optional, type=float
If this keyword is set to a value other than zero, there will be a
delay of this many seconds between command execution. This will permit
"movies" of command sequences to be displayed.
cmdindex: in, optional, type=integer
This keyword is used to select which command in an cgWindow to act on
when the AllCmd, DeleteCmd, LoadCmd and ReplaceCmd keywords are used.
See the descriptions of these keywords for details on what happens when
CmdIndex is missing.
deletecmd: in, optional, type=boolean, default=0
Set this keyword to delete a graphics command from an cgWindow.
If CmdIndex is undefined the last command entered into the window is
deleted. It is not possible to delete the last command in the window.
Use WinID to identify the cgWindow you are interested in. If WinID
is undefined, the last cgWindow created is used.
executecmd: in, optional, type=boolean, default=0
Set this keyword to immediate execute all the commands in an cgWindow.
Normally, this is used after commands have been loaded with LOADCMD.
group_leader: in, optional
The identifier of a widget to serve as a group leader for this program.
If the group leader is destroyed, this program is also destroyed. Used
when calling this program from another widget program.
listcmd: in, optional, type=boolean, default=0
If this keyword is set, the commands currently in the cgWindow are
listed. Use WinID to identify the cgWindow you are interested in.
If WinID is undefined, the last cgWindow created is used.
loadcmd: in, optional, type=boolean, default=0
Set this keyword to add an additional graphics command to an cgWindow.
The command is added to the last created cgWindow, unless the WinID
keyword is used to select another cgWindow. Loaded commands are not
automatically executed. Set the EXECUTECMD keyword at the end of loading
to execute the loaded commands. If CMDINDEX is used to select a command
index, the new command is loaded before the command currently occuping
that index in the command list.
method: in, optional, type=boolean, default=0
Set this keyword if the command is an object method call rather than a
procedure call. If this keyword is set, the first positional parameter, p1,
must be present and must be a valid object reference.
replacecmd: in, optional, type=boolean, default=0
Set this keyword to replace a graphics command from an cgWindow.
If CmdIndex is undefined, *all* commands in the window are replaced. Use
WinID to identify the cgWindow you are interested in. If WinID is
undefined, the last cgWindow created is used for the replacement.
waspect: in, optional, type=float, default=normal
Set this keyword to the aspect ratio you would like the window to have.
The aspect ratio is calculated as (ysize/xsize). Must be a float value.
If this keyword is set, the window will maintain this aspect ratio,
even when it is resized.
wbackground: in, optional, type=varies, default=!P.Background
The background color of the window. Specifying a background color
automatically sets the WErase keyword.
werase: in, optional, type=boolean, default=0
Set this keyword to cause the window to be erased before graphics commands
are drawn. This may need to be set, for example, to display images.
winid: in, optional, type=integer
Use this keyword to select the window cgWindow identifier (the number between
the parentheses in the title bar of cgWindow). The AddCmd, ReplaceCmd, ListCmd,
and DeleteCmd keywords will all apply to the commands in the last cgWindow
created unless this keyword is used to select another cgWindow to apply the
commands to.
wmulti: in, optional, type=intarr(5)
Set this keyword in exactly the same way you would set the !P.Multi keyword.
It will allow you to display multi-plots in the cgWindow graphics window.
wobject: out, optional, type=object
cgWindow creates a FSC_CmdWindow object. This object reference is returned
if this keyword is present.
woxmargin: in, optional, type=float
A two-element array indicating the left and right X outside margins for the
graphical display. Used only when doing multiple plots with `WMulti`.
woymargin: in, optional, type=float
A two-element array indicating the bottom and top Y outside margins for the
graphical display. Used only when doing multiple plots with `WMulti`.
wxpos: in, optional, type=integer, default=5
The x offset in device coordinates of the cgWindow from the upper-left corner of the display.
wypos: in, optional, type=integer, default=5
The y offset in device coordinates of the cgWindow from the upper-left corner of the display.
wxsize: in, optional, type=integer, default=640
The x size in device coordinates of the graphics window.
wysize: in, optional, type=integer, default=5
The y size in device coordinates of the the graphics window.
wtitle: in, optional, type=string, default='Resizeable Graphics Window'
The title of the graphics window. A window index number is appended to the
title so multiple cgWindow programs can be selected.

:Examples:
Test code::
data = cgDemoData(17)
cgWindow, 'cgPlot', data, COLOR='red'
cgWindow, 'cgPlot', data, PSYM=2, /Overplot, COLOR='dodger blue', /AddCmd
cgWIndow, 'cgPlot', cgDemoData(17), color='olive', linestyle = 2, /Overplot, /AddCmd
cgWindow, /ListCmd
cgWindow, 'cgPlot', data, COLOR='purple', /ReplaceCMD, CMDINDEX=0

Additional examples can be found here::

http://www.idlcoyote.com/graphics_tips/cgwindow.html

Example using different keyword parameters for the display and PostScript output::

IDL> cgPlot, cgDemoData(1), /WINDOW, $
THICK=1.0, XTITLE='Distance (' + Greek('mu') + 'm)', $
ALTPS_KEYWORDS={THICK:4.0, XTITLE:'Distance (' + Greek('mu', /PS) + 'm)'}

Example using different positional parameters::

IDL> cgText, 0.20, 0.85, /Normal, 'Line of Text', ALIGNMENT=0.0, $
ALTPS_KEYWORDS={ALIGNMENT:1.0}, ALTPS_PARAMS={P1:0.88}, /ADDCMD

Additional examples can be found here::

http://www.idlcoyote.com/cg_tips/kwexpressions.php

:History:
Change History::
Written, 17 January 2011. DWF.
Fixed a problem with the example code, and added EMPTY to end of Draw method
to force UNIX machines to empty the graphics buffer after CALL_PROCEDURE. 20 Jan 2011. DWF.
Improved documentation and error handling. 19 Jan 2011. DWF.
More improved error handling and messages. 26 Jan 2011. DWF.
Made changes to accommodate the new cgControl routine. 27 Jan 2011. DWF.
Added WXOMARGIN and WYOMARGIN keywords. 28 Jan 2011. DWF.
Numerous changes leading up to official release. 4 Feb 2011. DWF.
Added workaround for UNIX bug for draw widget creation. 5 Feb 2011. DWF.
Corrected a window aspect ratio problem with PostScript output by making the
window the current window before calling PS_Start. 17 Feb 2011. DWF.
Added machinery for programmatically generating raster files. 18 Feb 2011. Jeremy Bailin.
Problem with restoring visualizations fixed. 6 March 2011. DWF.
Fixed a problem with CALL_METHOD, which requires one positional parameter. 8 March 2011. DWF.
Added the ability to set and unset adjustable text size in the window. 24 April 2011. DWF.
Fixed a problem in the ReplaceCommand method that had input parameters reversed. 6 May 2011. DWF.
Added the ability to set the dimensions of the draw widget programmatically. 14 June 2011.
Added the keywords EvalKeywords and EvalParams to allow evaluation of command parameters and
keywords at run-time. See http://www.idlcoyote.com/cg_tips/kwexpressions.php for
additional details and explanations of how these keywords should be used. 2 Aug 2011.
Problem dereferencing a null pointer in DRAW method fixed. 3 Aug 2011. DWF.
Changes to handle inability to create raster files from PS encapsulated files in
landscape mode. 26 Aug 2011. DWF.
Added ability to set PostScript color mode. 30 Aug 2011. DWF.
The method I was using for evaluating keyword and argument parameters at run-time
was just WAY too complicated and difficult to use. I have eliminated this
method (along with the EvalKeywords and EvalParams) in favor of a method that
allows the user to supply alternative values to use in the PostScript device.
This uses keywords AltPS_Keywords and AltPS_Params to collect these alternative
arguments in structures that can be used at run-time to supply alternative values.
As before, this is explained in detail at http://www.idlcoyote.com/cg_tips/kwexpressions.php.
1 Sept 2011. DWF.
Missed a couple of places to set decomposition color mode. 7 Sept 2011. DWF.
Fixed a problem with improper filename when creating raster file vis
Imagemagick via cgControl. 10 Oct 2011. DWF.
Added WASPECT keyword to allow window aspect ratio to be set. 9 Nov 2011. DWF.
Added PDF file to the Save As menu. Requires Ghostscript to be installed on some machines. 6 Dec 2011. DWF.
Added modifications to allow PDF files to be programmatically created from cgControl. 11 Dec 2011. DWF.
Added the ability to specify a fourth positional parameter. 6 Jan 2012. DWF.
Separated off the cgCmdWindow part of the code to make an object-widget draw widget. 19 Jan 2012. DWF.
Fixed a small type with the Outside Margin keywords that was preventing these from being used. 19 April 2012. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgwindow.pro)

CGWINDOW_GETDEFS

   Allows the user to get the global defaults for resizeable cgWindow programs.

 :Categories:
    Graphics
    
 :Keywords:
     adjustsize: out, optional, type=boolean
         If set, adjust the default text size to match the display window size.
     aspect: out, optional, type=float
         The aspect ratio of the window.
     background: out, optional, type=string
         The background color of the window.
     delay: out, optional, type=float
          The amount of delay between command execution.
     eraseit: out, optional, type=boolean
         The Erase status of the window.
     im_density: out, optional, type=integer
         The sampling density.
     im_png8: out, optional, type=boolean
         If set, ImageMagick will create 8-bit PNG files, rather than 24-bit.
     im_options: out, optional, type=string
         Current ImageMagick convert options.
     im_raster: out, optional, type=boolean
         The raster via ImageMagick setting.
     im_resize: out, optional, type=integer
         The amount PostScript output is resized.
     im_transparent: out, optional, type=boolean
         The transparent background setting.
     im_width: out, optional, type=integer
         The final width of ImageMagick raster file output.
     multi: out, optional, type=Intarr(5)
         The !P.MULTI setting for the window.
     palette: out, optional, type=byte
         The window color palette.
     pdf_path: out, optional, type=string
         The name of the path to the Ghostscript command for converting PS to PDF.
     pdf_unix_convert_cmd: out, optional, type=string
         The name of an alternative UNIX command to convert PostScript to PDF.
     ps_charsize: out, optional, type=float, default=0.0
         The PostScript character size.
     ps_decomposed: out, optional, type=boolean
         The PostScript decomposed status of the window.
     ps_delete: out, optional, type=boolean
         The delete PostScript file status of the window.
     ps_encapsulated: out, optional, type=boolean
          The PostScript encapsulated status of the window.
     ps_font: out, optional, type=integer
          The font being using for PostScript output.
     ps_metric: out, optional, type=boolean
          The metric status of the window.
     ps_quiet: out, optional, type=boolean
          Set to one of the QUIET keyword is set on PSConfig.
     ps_scale_factor: out, optional, type=float
          The PostScript scale factor.
     ps_tt_font: out, optional, type=string
          The name of the PostScript true-type font in current use.
     title: out, optional, type=boolean
         The window title. 
     xomargin: out, optional, type=intarr(2)
         The !X.OMargin value for multiplots.
     xpos: out, optional, type=integer
         The X offset of the window from the upper-left corner of the display.
     xsize: out, optional, type=integer
         The starting X size of the window.
     yomargin: out, optional, type=intarr(2)
         The !Y.OMargin value for multiplots.
     ypos: out, optional, type=integer
         The Y offset of the window from the upper-left corner of the display.
     ysize: out, optional, type=integer
         The starting Y size of the window.
          
 :Examples:
    Used to get cgWindow global properties::
       IDL> cgWindow_GetDefs, PALETTE=palette, PS_ENCAPSULATED=encap, PS_METRIC=metric
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 29 January 2011. DWF.
        Added PS_QUIET keyword. 17 Feb 2011. DWF.
        Added Raster_IM.  18 Feb 2011. Jeremy Bailin
        Added the ability to set and unset adjustable text size in 
          cgWindow with ADJUSTSIZE keyword. 24 April 2011. DWF.
        Added PS_DECOMPOSED keyword to allow getting/setting of PostScript decomposed 
          value. 30 Aug 2011. DWF.
        Added ASPECT keyword to allow getting/setting of window aspect ratio. 18 Nov 2011. DWF.
        Added PDF_UNIX_CONVERT_CMD and PDF_PATH keywords. 7 Dec 2011. DWF.
        Added IM_WIDTH keyword. 3 April 2012. DWF.
        Added IM_PNG8 keyword. 3 April 2012. DWF.

 :Copyright:
     Copyright (c) 2011-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgwindow_getdefs.pro)

CGWINDOW_SETDEFS

Allows the user to set global defaults for resizeable cgWindow programs.

:Categories:
Graphics

:Keywords:
adjustsize: in, optional, type=boolean, default=0
Set this keyword to have the default text size adjusted to fit the size of the
display window.
aspect: in, optional, type=float, default=0.0
Set the aspect ratio of the window. If set to 0, the normal "default" window
aspect ratio is used and nothing special is done when the window is resize.
If aspect is not 0, then the window is confined to this aspect ratio.
background: in, optional, type=string
The background color of the window. Only use if the ERASEIT property is also set.
delay: in, optional, type=float, default=0
Set this keyword to the amount of delay desired between command execution. 0
eraseit: in, optional, type=boolean
If this property is set, the cgWindow erases with the background color before
displaying the commands in the window's command list.
im_density: in, optional, type=integer, default=300
Set this keyword to the sampling density when ImageMagick creates raster image
file from PostScript outout.
im_options: in, optional, type=string, default=""
Set this keyword to any ImageMagick options you would like to pass along to the
ImageMagick convert command when creating raster image files from PostScript output.
im_raster: in, optional, type=boolean, default=1 (if ImageMagick is found)
When raster files are created programmatically, this keyword determines if the
raster file is created directly in IDL (value =0) or is created from a PostScript
intermediate file via ImageMagick (value =1). The default is via ImageMagick if the
convert program can be found on the machine running the program.
im_resize: in, optional, type=integer, default=25
Set this keyword to percentage that the raster image file created my ImageMagick
from PostScript output should be resized.
im_transparent: in, optional, type=boolean, default=0
Set this keyword to allow ImageMagick to create transparent backgrounds when it
makes raster image files from PostScript output.
im_width: in, optional, type=integer
Set this keyword to the width of the output raster file in pixel units. The height of the raster
file is set to preserve the aspect ratio of the output image. Applies only to raster images (eg
PNG, JPEG, TIFF, etc.) created from PostScript files with ImageMagick.
multi: in, optional, type=Intarr(5)
Set this keyword to the !P.MULTI setting you want to use for the window.
!P.MULTI is set to this setting before command execution, and set back to
it's default value when the commands are finished executing.
palette: in, optional, type=byte
Use this keyword to pass in an N-by-3 (or 3-by-N) byte array containing the
R, G, and B vectors of a color table. It is probably easier to use cgLoadCT or
XCOLORS to load color tables for the window, but this is provided as another option.
pdf_path: out, optional, type=string
Set this keyword to the name of the path to the Ghostscript command for converting PS to PDF.
pdf_unix_convert_cmd: out, optional, type=string
Set this keyword to the name of an alternative UNIX command to convert PostScript to PDF.
ps_charsize: in, optional, type=float, default=0.0
Set this value to the !P.Charsize value to use when creating PostScript output. This
value is not used if !P.Charsize is set to anything other than 0.0.
ps_decomposed: in, optional, type=boolean
If set, use decomposed color in the PostScript device.
ps_delete: in, optional, type=boolean, default=1
Set this keyword to zero if you want to keep the PostScript output ImageMagick creates
when making raster file output.
ps_encapsulated: in, optional, type=boolean, default=0
Set this keyword to configure PSCONFIG to produce encapsulated PostScript output by default.
ps_font: in, optional, type=integer, default=0
Set this to the !P.Font value to use for creating PostScript files.
ps_metric: in, optional, type=boolean, default=0
Set this keyword to configure PSCONFIG to use metric values and A4 page size in its interface.
ps_quiet: in, optional, type=boolean, default=0
Set this keyword to suppress output messages from PS_Start and PS_End.
ps_scale_factor: in, optional, type=float, default=1.0
Set this keyword to the PostScript scale factor you want to use for PostScript output.
ps_tt_font: in, optional, type=string, default="Helvetica"
Set this keyword to the name of the PostScript true-type font to use for PostScript output.
Not used, unless !P.Font=1.
reset: in, optional, type=boolean, default=0
Set this keyword to reset all values to their default values.
title: in, optional, type=boolean
If this keyword is set, the selection is assumed to be a window title. All
matching is done in uppercase characters.
xomargin: in, optional, type=intarr(2)
Set this keyword to set !X.OMargin to this value for multiplots.
xpos: in, optional, type=integer
Set this keyword to the X offset of the window from the upper-left corner of the display.
xsize: in, optional, type=integer, default=640
Set this keyword to the starting X size of the window.
yomargin: in, optional, type=intarr(2)
Set this keyword to set !Y.OMargin to this value for multiplots.
ypos: in, optional, type=integer
Set this keyword to the Y offset of the window from the upper-left corner of the display.
ysize: in, optional, type=integer, default=512
Set this keyword to the starting Y size of the window.

:Examples:
Used to set cgWindow global properties::
IDL> cgLoadCT, 5, RGB_TABLE=palette
IDL> cgWindow_SetDefs, PALETTE=palette, $
ERASEIT=1, XSIZE=800, YSIZE=400, XPOS=100, YPOS=200, $
PS_ENCAPSULATED=1, PS_METRIC=1
IDL> cgImage, cgDemoData(7), /WINDOW, MARGIN=0.1

:History:
Change History::
Written, 29 January 2011. DWF.
Small bug fixes, and addition of PS_QUIET keyword. 17 Feb 2011. DWF.
Added Raster_IM, 18 February 2011. Jeremy Bailin.
Added the ability to set and unset adjustable text size in
cgWindow with ADJUSTSIZE keyword. 24 April 2011. DWF.
Added PS_DECOMPOSED keyword to set the PostScript color mode. 30 Aug 2011. DWF.
Added ASPECT keyword to allow getting/setting of window aspect ratio. 18 Nov 2011. DWF.
Added PDF_UNIX_CONVERT_CMD and PDF_PATH keywords. 7 Dec 2011. DWF.
Added IM_WIDTH keyword. 3 April 2012. DWF.
Added IM_PNG8 keyword. 3 April 2012. DWF.

:Copyright:
Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/cgwindow_setdefs.pro)

CHECKSUM32

 NAME:
       CHECKSUM32

 PURPOSE:
       To compute the 32bit checksum of an array (ones-complement arithmetic)

 EXPLANATION:
       The 32bit checksum is adopted in the FITS Checksum convention
       http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/checksum.html

 CALLING SEQUENCE:
       CHECKSUM32, array, checksum, [/FROM_IEEE, /NoSAVE]

 INPUTS:
       array - any numeric idl array.  If the number of bytes in the array is 
               not a multiple of four then it is padded with zeros internally
               (the array is returned unchanged).   Convert a string array 
               (e.g. a FITS header) to bytes prior to calling CHECKSUM32.

 OUTPUTS:
       checksum - unsigned long scalar, giving sum of array elements using 
                  ones-complement arithmetic
 OPTIONAL INPUT KEYWORD:

      /FROM_IEEE - If this keyword is set, then the input is assumed to be in
           big endian format (e.g. an untranslated FITS array).   This keyword
           only has an effect on little endian machines (e.g. Linux boxes).

      /NoSAVE - if set, then the input array is not saved upon exiting.   Use 
           the /NoSave keyword to save time if the input array is not needed 
           in further computations. 
 METHOD:
       Uses TOTAL() to sum the array into a double precision variable.  The
       overflow bits beyond 2^32 are then shifted back to the least significant
       bits.    Due to the limited precision of a DOUBLE variable, the summing
       is done in chunks determined by MACHAR(). Adapted from FORTRAN code in
      heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/general/checksum/node30.html

      Could probably be done in a cleverer way (similar to the C
      implementation) but then the array-oriented TOTAL() function could not 
      be used.
 RESTRICTIONS:
       (1) Not valid for object or pointer data types
 EXAMPLE:
       Find the 32 bit checksum of the array x = findgen(35)

       IDL> checksum32, x, s    ===> s =  2920022024
 FUNCTION CALLED:
       HOST_TO_IEEE, IS_IEEE_BIG(), N_BYTES()
 MODIFICATION HISTORY:
       Written    W. Landsman          June 2001
       Work correctly on little endian machines, added /FROM_IEEE and /NoSave
                  W. Landsman          November 2002
       Pad with zeros when array size not a multiple of 4 W.Landsman Aug 2003
       Always copy to new array, somewhat slower but more robust algorithm
           especially for Linux boxes   W. Landsman Sep. 2004 
       Sep. 2004 update not implemented correctly (sigh) W. Landsman Dec 2004         
       No need to byteswap 4 byte datatypes on little endian W. L. May 2009
       Use /INTEGER keyword to TOTAL() function W.L. June 2009

(See $IDLUTILS_DIR/goddard/pro/misc/checksum32.pro)

CHECK_FITS

 NAME:
       CHECK_FITS
 PURPOSE:
       Check that keywords in a FITS header array match the associated data  
 EXPLANATION:
       Given a FITS array IM, and a associated FITS header HDR, this
       procedure will check that
               (1) HDR is a string array, and IM is defined and numeric   
               (2) The NAXISi values in HDR are appropriate to the dimensions 
                   of IM
               (3) The BITPIX value in HDR is appropriate to the datatype of IM
       If the /UPDATE keyword is present, then the FITS header will be 
       modified, if necessary, to force agreement with the image array

 CALLING SEQUENCE:
       check_FITS, im, hdr, [ dimen, idltype, /UPDATE, /NOTYPE, /SILENT
                              ERRMSG = ]'

 INPUT PARAMETERS:
       IM -  FITS array, e.g. as read by READFITS
       HDR - FITS header (string array) associated with IM

 OPTIONAL OUTPUTS:
       dimen - vector containing actual array dimensions
       idltype- data type of the FITS array as specified in the IDL SIZE
               function (1 for BYTE, 2 for INTEGER*2, 3 for INTEGER*4, etc.)

 OPTIONAL KEYWORD INPUTS:
       /NOTYPE - If this keyword is set, then only agreement of the array
               dimensions with the FITS header are checked, and not the 
               data type.
       /UPDATE - If this keyword is set then the BITPIX, NAXIS and NAXISi
               FITS keywords will be updated to agree with the array
       /FITS, /SDAS -  these are obsolete keywords that now do nothing 
       /SILENT - If keyword is set and nonzero, the informational messages 
               will not be printed
 OPTIONAL KEYWORD OUTPUT:
       ERRMSG  = If this keyword is present, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.  

 PROCEDURE:
       Program checks the NAXIS and NAXISi keywords in the header to
       see if they match the image array dimensions, and checks whether
       the BITPIX keyword agrees with the array type.

 PROCEDURE CALLS:
       FXADDPAR, FXPAR(), SXDELPAR
 MODIFICATION HISTORY:
       Written, December 1991  W. Landsman Hughes/STX to replace CHKIMHD
       No error returned if NAXIS=0 and IM is a scalar   W. Landsman  Feb 93
       Fixed bug for REAL*8 STSDAS data W. Landsman July 93
       Make sure NAXIS agrees with NAXISi  W. Landsman  October 93
        Converted to IDL V5.0   W. Landsman   September 1997
       Allow unsigned data types   W. Landsman December 1999
       Allow BZERO = 0 for unsigned data types   W. Landsman January 2000
       Added ERRMSG keyword, W. Landsman February 2000
       Use FXADDPAR to put NAXISi in proper order   W. Landsman August 2000
       Improper FXADDPAR call for DATATYPE keyword  W. Landsman December 2000
       Remove explicit setting of obsolete !err W. Landsman February 2004
       Remove SDAS support   W. Landsman       November 2006
       Fix dimension errors introduced Nov 2006
       Work again for null arrays W. Landsman/E. Hivon May 2007
       Use V6.0 notation  W.L.  Feb. 2011

(See $IDLUTILS_DIR/goddard/pro/fits/check_fits.pro)

CIC

 NAME:
       CIC

 PURPOSE:
       Interpolate an irregularly sampled field using Cloud in Cell method

 EXPLANATION:
       This function interpolates an irregularly sampled field to a
       regular grid using Cloud In Cell (nearest grid point gets
       weight 1-dngp, point on other side gets weight dngp, where
       dngp is the distance to the nearest grid point in units of the
       cell size).

 CATEGORY:
       Mathematical functions, Interpolation

 CALLING SEQUENCE:
       Result = CIC, VALUE, POSX, NX[, POSY, NY, POSZ, NZ, 
                     AVERAGE = average, WRAPAROUND =  wraparound,
                     ISOLATED = isolated, NO_MESSAGE = no_message]

 INPUTS:
       VALUE: Array of sample weights (field values). For e.g. a
              temperature field this would be the temperature and the
              keyword AVERAGE should be set. For e.g. a density field
              this could be either the particle mass (AVERAGE should
              not be set) or the density (AVERAGE should be set).
       POSX:  Array of X coordinates of field samples, unit indices: [0,NX>.
       NX:    Desired number of grid points in X-direction.
       
 OPTIONAL INPUTS:
      POSY: Array of Y coordinates of field samples, unit indices: [0,NY>.
      NY:   Desired number of grid points in Y-direction.
      POSZ: Array of Z coordinates of field samples, unit indices: [0,NZ>.
      NZ:   Desired number of grid points in Z-direction.

 KEYWORD PARAMETERS:
       AVERAGE:    Set this keyword if the nodes contain field samples
                   (e.g. a temperature field). The value at each grid
                   point will then be the weighted average of all the
                   samples allocated to it. If this keyword is not
                   set, the value at each grid point will be the
                   weighted sum of all the nodes allocated to it
                   (e.g. for a density field from a distribution of
                   particles). (D=0). 
       WRAPAROUND: Set this keyword if you want the first grid point
                   to contain samples of both sides of the volume
                   (see below).
       ISOLATED:   Set this keyword if the data is isolated, i.e. not
                   periodic. In that case total `mass' is not conserved.
                   This keyword cannot be used in combination with the
                   keyword WRAPAROUND.
       NO_MESSAGE: Suppress informational messages.

 Example of default allocation of nearest grid points: n0=4, *=gridpoint.

     0   1   2   3     Index of gridpoints
     *   *   *   *     Grid points
   |---|---|---|---|   Range allocated to gridpoints ([0.0,1.0> --> 0, etc.)
   0   1   2   3   4   posx

 Example of ngp allocation for WRAPAROUND: n0=4, *=gridpoint.

   0   1   2   3         Index of gridpoints
   *   *   *   *         Grid points
 |---|---|---|---|--     Range allocated to gridpoints ([0.5,1.5> --> 1, etc.)
   0   1   2   3   4=0   posx


 OUTPUTS:
       Prints that a CIC interpolation is being performed of x
       samples to y grid points, unless NO_MESSAGE is set. 

 RESTRICTIONS:
       Field data is assumed to be periodic with the sampled volume
       the basic cell, unless ISOLATED is set.
       All input arrays must have the same dimensions.
       Postition coordinates should be in `index units' of the
       desired grid: POSX=[0,NX>, etc.
       Keywords ISOLATED and WRAPAROUND cannot both be set.

 PROCEDURE:
       Nearest grid point is determined for each sample.
       CIC weights are computed for each sample.
       Samples are interpolated to the grid.
       Grid point values are computed (sum or average of samples).
 NOTES:
       Use tsc.pro for a higher-order interpolation scheme, ngp.pro for a lower
       order interpolation scheme.    A standard reference for these 
       interpolation methods is:   R.W. Hockney and J.W. Eastwood, Computer 
       Simulations Using Particles (New York: McGraw-Hill, 1981).
 EXAMPLE:
       nx=20
       ny=10
       posx=randomu(s,1000)
       posy=randomu(s,1000)
       value=posx^2+posy^2
       field=cic(value,posx*nx,nx,posy*ny,ny,/average)
       surface,field,/lego

 MODIFICATION HISTORY:
       Written by Joop Schaye, Feb 1999.
       Avoid integer overflow for large dimensions P.Riley/W.Landsman Dec. 1999

(See $IDLUTILS_DIR/goddard/pro/math/cic.pro)

CIRRANGE

 NAME:
       CIRRANGE
 PURPOSE:
       To force an angle into the range 0 <= ang < 360.
 CALLING SEQUENCE:
       CIRRANGE, ang, [/RADIANS]

 INPUTS/OUTPUT:
       ang     - The angle to modify, in degrees.  This parameter is
                 changed by this procedure.  Can be a scalar or vector.
                 The type of ANG is always converted to double precision
                 on output.

 OPTIONAL INPUT KEYWORDS:
       /RADIANS - If present and non-zero, the angle is specified in
                 radians rather than degrees.  It is forced into the range
                 0 <= ang < 2 PI.
 PROCEDURE:
       The angle is transformed between -360 and 360 using the MOD operator.   
       Negative values (if any) are then transformed between 0 and 360
 MODIFICATION HISTORY:
       Written by Michael R. Greason, Hughes STX, 10 February 1994.
       Get rid of WHILE loop, W. Landsman, Hughes STX, May 1996
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/cirrange.pro)

CLEANPLOT

 NAME:
       CLEANPLOT
 PURPOSE:
       Reset all plotting system variables (!P,!X,!Y,!Z) to their default values
 EXPLANATION:
       Reset all system variables (!P,!X,!Y,!Z) which are set by the user
       and which affect plotting to their default values.

 CALLING SEQUENCE:
       Cleanplot, [ /Silent, /ShowOnly]

 INPUTS:       
       None

 OPTIONAL KEYWORD INPUT:
       /SHOWONLY - If set, then CLEANPLOT will display the plotting system
                 variables with nondefault values, but it will not reset them.
               
       /SILENT - If set, then CLEANPLOT will not display a message giving the 
                 the system variables tags being reset.    One cannot set 
                  both /SILENT and /SHOWONLY
 OUTPUTS:      
       None

 SIDE EFFECTS: 
       The system variables that concern plotting are reset to their default
       values.  A message is output for each variable changed.
       The !P.CLIP and CRANGE, S, WINDOW, and REGION fields of the
       !X, !Y, and !Z system variables are not checked since these are
       set by the graphics device and not by the user.   

 PROCEDURE:
       This does NOT reset the plotting device.
       This does not change any system variables that don't control plotting.

 RESTRICTIONS:
       If user default values for !P, !X, !Y and !Z are different from
       the defaults adopted below, user should change P_old etc accordingly

 MODIFICATION HISTORY:
       Written IDL Version 2.3.0  W. Landsman & K. Venkatakrishna May '92
       Handle new system variables in V3.0.0     W. Landsman   Dec 92
       Assume user has at least V3.0.0           W. Landsman   August 95
       V5.0 has 60 instead of 30 TICKV values    W. Landsman   Sep. 97
       Change !D.N_COLORS to !D.TABLE_SIZE for 24 bit displays
               W. Landsman  April 1998
       Added silent keyword to supress output & modified X_old to
       handle the new !X and !Y tags in IDL 5.4   S. Penton     July 2000
       Test for visual depth if > V5.1   W. Landsman     July 2000
       Macs can report a visual depth of 32  W. Landsman  March 2001
       Call device,get_visual_depth only for device which allow it 
                W. Landsman  June 2001
       Default !P.color is 16777215 for 16 bit systems 
                       W. Landsman/M. Hadfield   November 2001 
       Added ShowOnly keyword   W. Landsman      April 2002
       Use V6.0 notation W. Landsman April 2011

(See $IDLUTILS_DIR/goddard/pro/plot/cleanplot.pro)

CNTRD

  NAME: 
       CNTRD
  PURPOSE:
       Compute the centroid  of a star using a derivative search 
 EXPLANATION:
       CNTRD uses an early DAOPHOT "FIND" centroid algorithm by locating the 
       position where the X and Y derivatives go to zero.   This is usually a 
       more "robust"  determination than a "center of mass" or fitting a 2d 
       Gaussian  if the wings in one direction are affected by the presence
       of a neighboring star.

  CALLING SEQUENCE: 
       CNTRD, img, x, y, xcen, ycen, [ fwhm , /KEEPCENTER, /SILENT, /DEBUG
                                       EXTENDBOX = ]

  INPUTS:     
       IMG - Two dimensional image array
       X,Y - Scalar or vector integers giving approximate integer stellar 
             center

  OPTIONAL INPUT:
       FWHM - floating scalar; Centroid is computed using a box of half
               width equal to 1.5 sigma = 0.637* FWHM.  CNTRD will prompt
               for FWHM if not supplied

  OUTPUTS:   
       XCEN - the computed X centroid position, same number of points as X
       YCEN - computed Y centroid position, same number of points as Y, 
              floating point

       Values for XCEN and YCEN will not be computed if the computed
       centroid falls outside of the box, or if the computed derivatives
       are non-decreasing.   If the centroid cannot be computed, then a 
       message is displayed and XCEN and YCEN are set to -1.

  OPTIONAL OUTPUT KEYWORDS:
       /SILENT - Normally CNTRD prints an error message if it is unable
               to compute the centroid.   Set /SILENT to suppress this.
       /DEBUG - If this keyword is set, then CNTRD will display the subarray
               it is using to compute the centroid.
       EXTENDBOX = {non-negative positive integer}.   CNTRD searches a box with
              a half width equal to 1.5 sigma  = 0.637* FWHM to find the 
              maximum pixel.    To search a larger area, set EXTENDBOX to 
              the number of pixels to enlarge the half-width of the box.
              Default is 0; prior to June 2004, the default was EXTENDBOX= 3
       /KeepCenter = By default, CNTRD finds the maximum pixel in a box 
              centered on the input X,Y coordinates, and then extracts a new
              box about this maximum pixel.   Set the /KeepCenter keyword  
              to skip then step of finding the maximum pixel, and instead use
              a box centered on the input X,Y coordinates.                          
  PROCEDURE: 
       Maximum pixel within distance from input pixel X, Y  determined 
       from FHWM is found and used as the center of a square, within 
       which the centroid is computed as the value (XCEN,YCEN) at which 
       the derivatives of the partial sums of the input image over (y,x)
       with respect to (x,y) = 0.    In order to minimize contamination from
       neighboring stars stars, a weighting factor W is defined as unity in 
       center, 0.5 at end, and linear in between 

  RESTRICTIONS:
       (1) Does not recognize (bad) pixels.   Use the procedure GCNTRD.PRO
           in this situation. 
       (2) DAOPHOT now uses a newer algorithm (implemented in GCNTRD.PRO) in 
           which centroids are determined by fitting 1-d Gaussians to the 
           marginal distributions in the X and Y directions.
       (3) The default behavior of CNTRD changed in June 2004 (from EXTENDBOX=3
           to EXTENDBOX = 0).
       (4) Stone (1989, AJ, 97, 1227) concludes that the derivative search
           algorithm in CNTRD is not as effective (though faster) as a 
            Gaussian fit (used in GCNTRD.PRO).
  MODIFICATION HISTORY:
       Written 2/25/86, by J. K. Hill, S.A.S.C., following
       algorithm used by P. Stetson in DAOPHOT.
       Allowed input vectors        G. Hennessy       April,  1992
       Fixed to prevent wrong answer if floating pt. X & Y supplied
               W. Landsman        March, 1993
       Convert byte, integer subimages to float  W. Landsman  May 1995
       Converted to IDL V5.0   W. Landsman   September 1997
       Better checking of edge of frame David Hogg October 2000
       Avoid integer wraparound for unsigned arrays W.Landsman January 2001
       Handle case where more than 1 pixel has maximum value W.L. July 2002
       Added /KEEPCENTER, EXTENDBOX (with default = 0) keywords WL June 2004
       Some errrors were returning X,Y = NaN rather than -1,-1  WL Aug 2010

(See $IDLUTILS_DIR/goddard/pro/idlphot/cntrd.pro)

COLOR24

 The purpose of this function is to convert a RGB color triple
 into the equivalent 24-bit long integer. The 24-bit integer
 can be decomposed into the appropriate color by interpreting
 the lowest 8 bits as red, the middle 8 bits as green, and the
 highest 8 bits as blue. This routine was written to be used with 
 device-independent color programs like `cgColor`.
 
 :Categories:
    Graphics, Utilities
    
 :Params:
    color: in, required
       A three-element column or row array representing a color triple. Or an 
       N-by-three element array of color triples. The values of the elements 
       must be between 0 and 255.

 :Examples:
    To convert the color triple for the color YELLOW, (255, 255, 0), to the 
    hexadecimal value '00FFFF'x or the decimal number 65535, type::
    
       color = COLOR24([255, 255, 0])

 :Author:
    FANNING SOFTWARE CONSULTING::
       David W. Fanning 
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written by:  David Fanning, 3 February 96.
        Completely revised the algorithm to accept color arrays. 19 October 2000. DWF.
            
 :Copyright:
     Copyright (c) 1996-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/color24.pro)

COLORSAREIDENTICAL

 :Description:
   Returns a 1 if the two input colors refer to the same color, otherwise returns a 0.

 :Categories:
    Graphics Utility
    
 :Params:
    color_1: in, required, type=string/integer/long
         The first color to compare for "equality".
    color_2: in, required, type=string/integer/long
         The second color to compare for "equality".
       
 :Keywords:
     None.
          
 :Examples:
    Used to compare if two different colors are the same color::
       IDL> Print, ColorsAreIdentical('white', cgColor('white'))
       IDL> Print, ColorsAreIdentical(252, !P.Color)
       IDL> Print, ColorsAreIdentical('white', '255')
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 24 December 2010. DWF.
        Fixed a typo when first color is INTEGER and second color is STRING. 3 Jan 2011. DWF.
        Added error handling for out of bounds color values. 25 May 2011. DWF.

 :Copyright:
     Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/colorsareidentical.pro)

COMPARE_STRUCT

 NAME:
       COMPARE_STRUCT  
 PURPOSE:
       Compare all matching tag names and return differences

 EXPLANATION:
       Compare all matching Tags names (except for "except_Tags")
       between two structure arrays (may have different struct.definitions),
       and return a structured List of fields found different.

       The Exelis contrib library has a faster but less powerful procedure
       struct_equal.pro, see 
       http://www.exelisvis.com/Default.aspx?tabid=1540&id=1175

 CALLING SEQUENCE:
       diff_List = compare_struct( struct_A, struct_B [ EXCEPT=, /BRIEF,
                                    /FULL, /NaN, /RECUR_A, /RECUR_B )
 INPUTS:
       struct_A, struct_B : the two structure arrays to compare.
       Struct_Name : for internal recursion use only.
 OPTIONAL INPUT KEYWORDS:
               EXCEPT = string array of Tag names to ignore (NOT to compare).
               /BRIEF = number of differences found for each matching field
                                               of two structures is printed.
               /FULL = option to print even if zero differences found.
               /NaN = if set, then tag values are considered equal if they
                      are both set to NaN 
               /RECUR_A = option to search for Tag names
                               in sub-structures of struct_A,
                               and then call compare_struct recursively
                               for those nested sub-structures.
               /RECUR_B = search for sub-structures of struct_B,
                               and then call compare_struct recursively
                               for those nested sub-structures.
       Note:
               compare_struct is automatically called recursively
               for those nested sub-structures in both struct_A and struct_B
               (otherwise cannot take difference)
 OUTPUT:
       Returns a structure array describing differences found.   
       which can be examined using print,diff_List or help,/st,diff_List.
       The tags are
       TAG_NUM_A - the tag number in structure A
       TAG_NUM_B - the tag number in structure B
       FIELD - the tag name
       NDIFF - number of differences (always 1 for a scalar tag).
 PROCEDURE:
       Match Tag names and then use where function on tags.
 EXAMPLE:
       Find the tags in the !X system variable which are changed after a 
       simple plot.
       IDL> x = !X              ;Save original values
       IDL> plot, indgen(25)    ;Make a simple plot
       IDL> help,/str,compare_struct(x,!X)    ;See how structure has changed

            and one will see that the tags  !X.crange and !X.S are changed
            by the plot.
 MODIFICATION HISTORY:
       written 1990 Frank Varosi STX @ NASA/GSFC (using copy_struct)
       modif Aug.90 by F.V. to check and compare same # of elements only.
       Added /NaN keyword W. Landsman  March 2004
       Don't test string for NaN values W. Landsman March 2008

(See $IDLUTILS_DIR/goddard/pro/structure/compare_struct.pro)

CONCAT_DIR()

 NAME:   
       CONCAT_DIR()
               
 PURPOSE:     
       To concatenate directory and file names for current OS.
 EXPLANATION:
       The given file name is appended to the given directory name with the 
       format appropriate to the current operating system.

 CALLING SEQUENCE:               
       result = concat_dir( directory, file) 

 INPUTS:
       directory  - the directory path (string)
       file       - the basic file name and extension (string)
                                   can be an array of filenames.

 OUTPUTS:     
       The function returns the concatenated string.  If the file input
       is a string array then the output will be a string array also.
               
 EXAMPLES:         
       IDL> pixfile = concat_dir('$DIR_GIS_MODEL','pixels.dat')

       IDL> file = ['f1.dat','f2.dat','f3.dat']
       IDL> dir = '$DIR_NIS_CAL'
       IDL> 


 RESTRICTIONS: 
               
       The version of CONCAT_DIR available at 
       http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/system/concat_dir.pro
       includes (mostly) additional VMS-specific keywords.

 CATEGORY    
        Utilities, Strings
               
 REVISION HISTORY:
       Prev Hist. : Yohkoh routine by M. Morrison
       Written     : CDS version by C D Pike, RAL, 19/3/93
       Version     : Version 1  19/3/93
       Documentation modified Nov-94   W. Landsman 
       Add V4.0 support for Windows    W. Landsman   Aug 95
       Converted to IDL V5.0   W. Landsman   September 1997
       Changed loops to long integer   W. Landsman   December 1998
       Added Mac support, translate Windows environment variables, 
       & treat case where dirname ends in '/' W. Landsman  Feb. 2000
       Assume since V5.5, remove VMS support W. Landsman  Sep. 2006

(See $IDLUTILS_DIR/goddard/pro/misc/concat_dir.pro)

CONS_DEC

 NAME:
       CONS_DEC
 PURPOSE:
       Obtain the X and Y coordinates of a line of constant declination
 EXPLANATION:
       Returns a set of Y pixels values, given an image with astrometry, and 
            either
       (1)  A set of X pixel values, and a scalar declination value, or
       (2)  A set of declination values, and a scalar X value

       Form (1) can be used to find the (X,Y) values of a line of constant
       declination.  Form (2) can be used to find the Y positions of a set
       declinations, along a line of constant X.

 CALLING SEQUENCE:
       Y = CONS_DEC( DEC, X, ASTR, [ ALPHA ])

 INPUTS:
       DEC - Declination value(s) in DEGREES (-!PI/2 < DEC < !PI/2).  
               If X is a vector, then DEC must be a scalar.
       X -   Specified X pixel value(s) for line of constant declination 
               If DEC is a vector, then X must be a scalar.
       ASTR - Astrometry structure, as extracted from a FITS header by the
               procedure EXTAST
 OUTPUT:
       Y   - Computed set of Y pixel values.  The number of Y values is the
               same as either DEC or X, whichever is greater.

 OPTIONAL OUTPUT:
       ALPHA - the right ascensions (DEGREES) associated with the (X,Y) points

 RESTRICTIONS:
       Implemented only for the TANgent, SIN and CAR projections

 NOTES:
       The algorithm (and notation) is based on AIPS Memo 27 by Eric Greisen,
       with modifications for a coordinate description (CD) matrix as 
       described in Paper II of Greisen & Calabretta (2002, A&A, 395, 1077).
       These documents are available from 
       http://www.cv.nrao.edu/fits/documents/wcs/wcs.html

 REVISION HISTORY:
       Written, Wayne Landsman  STX Co.                          April 1988
       Use new astrometry structure,     W. Landsman    HSTX     Jan. 1994
       Use CD matrix, add SIN projection   W. Landsman  HSTX     April, 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Fix case where DEC is scalar, X is vector   W. Landsman RITSS Feb. 2000
       Fix possible sign error introduced Jan. 2000   W. Landsman  May 2000
       Work for the CARee' projection W. Landsman   May 2003

(See $IDLUTILS_DIR/goddard/pro/astrom/cons_dec.pro)

CONS_RA

 NAME:
       CONS_RA
 PURPOSE:
       Obtain the X and Y coordinates of a line of constant right ascension
 EXPLANATION:
       Return a set of X pixel values given an image with astrometry, 
       and either
       (1) a set of Y pixel values, and a scalar right ascension (or 
           longitude), or
       (2) a set of right ascension values, and a scalar Y value.

       In usage (1), CONS_RA can be used to determine the (X,Y) values
       of a line of constant right ascension.  In usage (2), CONS_RA can
       used to determine the X positions of specified RA values, along a
       line of constant Y.

 CALLING SEQUENCE:
       X = CONS_RA( RA, Y, ASTR, [ DEC] )

 INPUTS:         
       RA -  Right Ascension value in DEGREES (0 < RA < 360.).  If Y is a
               vector, then RA must be a scalar
       Y -   Specified Y pixel value(s) for line of constant right ascension
               If RA is a vector, then Y must be a scalar
       ASTR - Astrometry structure as extracted from a FITS header by the 
               procedure EXTAST
 OUTPUTS
       X   - Computed set of X pixel values.   The number of elements of X
               is the maximum of the number of elements of RA and Y.
 OPTIONAL OUTPUT:
       DEC - Computed set of declinations (in DEGREES) for X,Y, coordinates
 NOTES:
       The algorithm (and notation) is based on AIPS Memo 27 by Eric Greisen,
       with modifications for a coordinate description (CD) matrix as 
       described in Paper II of Calabretta & Greisen (2002, A&A, 395, 1077).
       These documents are available from 
       http://www.cv.nrao.edu/fits/documents/wcs/wcs.html

 RESTRICTIONS:
       Implemented only for the TANgent, SIN and CARtesian projections 

 REVISION HISTORY:
       Written, Wayne Landsman  STX Co.        April, 1988
       Algorithm adapted from AIPS memo No. 27 by Eric Greisen
       New astrometry structure
       Converted to IDL V5.0   W. Landsman   September 1997
       Added SIN projection    W. Landsman   January 2000
       Fix possible sign error introduced Jan. 2000   W. Landsman  May 2000
       Work for the CARee' projection W. Landsman   May 2003
       For TAN projection ensure angles between -90 and 90 W. Landsman Jan 2008

(See $IDLUTILS_DIR/goddard/pro/astrom/cons_ra.pro)

CONVERT_TO_TYPE

 NAME:
       CONVERT_TO_TYPE

 PURPOSE:

       Converts its input argument to a specified data type.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Utilities

 CALLING SEQUENCE:

       result = Convert_To_Type(input, type)

 INPUT_PARAMETERS:

       input:          The input data to be converted.
       type:           The data type. Accepts values as given by Size(var, /TNAME) or Size(var, /TYPE).
                       If converting to integer types, values are truncated (similar to FLOOR keyword below),
                       unless keywords are set.

 OUTPUT_PARAMETERS:

      result:          The input data is converted to specified data type.

 KEYWORDS:

     CEILING:          If set and converting to an integer type, the CEIL function is applied before conversion.

     FLOOR:            If set and converting to an integer type, the FLOOR function is applied before conversion.

     ROUND:            If set and converting to an integer type, the ROUND function is applied before conversion.


 RESTRICTIONS:

     Data types STRUCT, POINTER, and OBJREF are not allowed.

 MODIFICATION HISTORY:

     Written by David W. Fanning, 19 February 2006.
     Typo had "UNIT" instead of "UINT". 23 February 2009. DWF.
     Added CEILING, FLOOR, and ROUND keywords. 1 April 2009. DWF.
     Modified so that the "type" variable is not changed by the program. 5 May 2009. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/convert_to_type.pro)

CONVOLVE

 NAME:
       CONVOLVE
 PURPOSE:
       Convolution of an image with a Point Spread Function (PSF)
 EXPLANATION:
       The default is to compute the convolution using a product of 
       Fourier transforms (for speed).

       The image is padded with zeros so that a large PSF does not
       overlap one edge of the image with the opposite edge of the image.

       This routine is now partially obsolete due to the introduction of  the
       intrinsic CONVOL_FFT() function in IDL 8.1

 CALLING SEQUENCE:

       imconv = convolve( image1, psf, FT_PSF = psf_FT )
  or:
       correl = convolve( image1, image2, /CORREL )
  or:
       correl = convolve( image, /AUTO )

 INPUTS:
       image = 2-D array (matrix) to be convolved with psf
       psf = the Point Spread Function, (size < or = to size of image).

       The PSF *must* be symmetric about the point
       FLOOR((n_elements-1)/2), where n_elements is the number of
       elements in each dimension.  For Gaussian PSFs, the maximum
       of the PSF must occur in this pixel (otherwise the convolution
       will shift everything in the image).

 OPTIONAL INPUT KEYWORDS:

       FT_PSF = passes out/in the Fourier transform of the PSF,
               (so that it can be re-used the next time function is called).
       FT_IMAGE = passes out/in the Fourier transform of image.

       /CORRELATE uses the conjugate of the Fourier transform of PSF,
               to compute the cross-correlation of image and PSF,
               (equivalent to IDL function convol() with NO rotation of PSF)

       /AUTO_CORR computes the auto-correlation function of image using FFT.

       /NO_FT overrides the use of FFT, using IDL function convol() instead.
               (then PSF is rotated by 180 degrees to give same result)

       /NO_PAD - if set, then do not pad the image to avoid edge effects.
               This will improve memory and speed of the computation at the 
               expense of edge effects.   This was the default method prior 
               to October 2009
 METHOD:
       When using FFT, PSF is centered & expanded to size of image.
 HISTORY:
       written, Frank Varosi, NASA/GSFC 1992.
       Appropriate precision type for result depending on input image
                               Markus Hundertmark February 2006
       Fix the bug causing the recomputation of FFT(psf) and/or FFT(image)
                               Sergey Koposov     December 2006
       Fix the centering bug
                               Kyle Penner        October 2009
       Add /No_PAD keyword for better speed and memory usage when edge effects
            are not important.    W. Landsman      March 2010
       Add warning when kernel type does not match integer array
             W. Landsman Feb 2012

(See $IDLUTILS_DIR/goddard/pro/image/convolve.pro)

COPY_STRUCT

 NAME:
	COPY_STRUCT
 PURPOSE:
 	Copy all fields with matching tag names from one structure to another
 EXPLANATION:
       COPY_STRUCT is similar to the intrinisc STRUCT_ASSIGN procedure but 
       has optional keywords to exclude or specify specific tags.
  
	Fields with matching tag names are copied from one structure array to 
	another structure array of different type.
	This allows copying of tag values when equating the structures of
	different types is not allowed, or when not all tags are to be copied.
	Can also recursively copy from/to structures nested within structures.
	Note that the number of elements in the output structure array
	is automatically adjusted to equal the length of input structure array.
	If this not desired then use pro copy_struct_inx which allows
	specifying via subscripts which elements are copied where in the arrays.

 CALLING SEQUENCE:

	copy_struct, struct_From, struct_To, NT_copied
	copy_struct, struct_From, struct_To, EXCEPT=["image","misc"]
	copy_struct, struct_From, struct_To, /RECUR_TANDEM

 INPUTS:
	struct_From = structure array to copy from.
	struct_To = structure array to copy values to.

 KEYWORDS:

	EXCEPT_TAGS = string array of tag names to ignore (to NOT copy).
		Used at all levels of recursion.

	SELECT_TAGS = tag names to copy (takes priority over EXCEPT).
		This keyword is not passed to recursive calls in order
		to avoid the confusion of not copying tags in sub-structures.

	/RECUR_FROM = search for sub-structures in struct_From, and then
		call copy_struct recursively for those nested structures.

	/RECUR_TO = search for sub-structures of struct_To, and then
		call copy_struct recursively for those nested structures.

	/RECUR_TANDEM = call copy_struct recursively for the sub-structures
		with matching Tag names in struct_From and struct_To
		(for use when Tag names match but sub-structure types differ).

 OUTPUTS:
	struct_To = structure array to which new tag values are copied.
	NT_copied = incremented by total # of tags copied (optional)

 INTERNAL:
	Recur_Level = # of times copy_struct calls itself.
		This argument is for internal recursive execution only.
		The user call is 1, subsequent recursive calls increment it,
		and the counter is decremented before returning.
		The counter is used just to find out if argument checking
		should be performed, and to set NT_copied = 0 first call.
 EXTERNAL CALLS:
	pro match	(when keyword SELECT_TAGS is specified)
 PROCEDURE:
	Match Tag names and then use corresponding Tag numbers.
 HISTORY:
	written 1989 Frank Varosi STX @ NASA/GSFC
 	mod Jul.90 by F.V. added option to copy sub-structures RECURSIVELY.
	mod Aug.90 by F.V. adjust # elements in TO (output) to equal
			# elements in FROM (input) & count # of fields copied.
	mod Jan.91 by F.V. added Recur_Level as internal argument so that
			argument checking done just once, to avoid confusion.
			Checked against Except_Tags in RECUR_FROM option.
	mod Oct.91 by F.V. added option SELECT_TAGS= selected field names.
	mod Aug.95 by W. Landsman to fix match of a single selected tag.
	mod Mar.97 by F.V. do not pass the SELECT_TAGS keyword in recursion.
	Converted to IDL V5.0   W. Landsman   September 1997
       mod May 01 by D. Schlegel use long integers

(See $IDLUTILS_DIR/goddard/pro/structure/copy_struct.pro)

COPY_STRUCT_INX

 NAME:
	COPY_STRUCT_INX
 PURPOSE:
	Copy matching tags & specified indices from one structure to another
 EXPLANATION:
 	Copy all fields with matching tag names (except for "except_Tags")
	from one structure array to another structure array of different type.
	This allows copying of tag values when equating the structures of
	different types is not allowed, or when not all tags are to be copied.
	Can also recursively copy from/to structures nested within structures.
	This procedure is same as copy_struct with option to
	specify indices (subscripts) of which array elements to copy from/to.
 CALLING SEQUENCE:

	copy_struct_inx, struct_From, struct_To, NT_copied, INDEX_FROM=subf

	copy_struct_inx, struct_From, struct_To, INDEX_FROM=subf, INDEX_TO=subto

 INPUTS:
	struct_From = structure array to copy from.
	struct_To = structure array to copy values to.

 KEYWORDS:

	INDEX_FROM = indices (subscripts) of which elements of array to copy.
		(default is all elements of input structure array)

	INDEX_TO = indices (subscripts) of which elements to copy to.
		(default is all elements of output structure array)

	EXCEPT_TAGS = string array of Tag names to ignore (to NOT copy).
		Used at all levels of recursion.

	SELECT_TAGS = Tag names to copy (takes priority over EXCEPT).
		This keyword is not passed to recursive calls in order
		to avoid the confusion of not copying tags in sub-structures.

	/RECUR_FROM = search for sub-structures in struct_From, and then
		call copy_struct recursively for those nested structures.

	/RECUR_TO = search for sub-structures of struct_To, and then
		call copy_struct recursively for those nested structures.

	/RECUR_TANDEM = call copy_struct recursively for the sub-structures
		with matching Tag names in struct_From and struct_To
		(for use when Tag names match but sub-structure types differ).

 OUTPUTS:
	struct_To = structure array to which new tag values are copied.
	NT_copied = incremented by total # of tags copied (optional)

 INTERNAL:
	Recur_Level = # of times copy_struct_inx calls itself.
		This argument is for internal recursive execution only.
		The user call is 1, subsequent recursive calls increment it,
		and the counter is decremented before returning.
		The counter is used just to find out if argument checking
		should be performed, and to set NT_copied = 0 first call.
 EXTERNAL CALLS:
	pro match	(when keyword SELECT_TAGS is specified)
 PROCEDURE:
	Match Tag names and then use corresponding Tag numbers,
	apply the sub-indices during = and recursion.
 HISTORY:
	adapted from copy_struct: 1991 Frank Varosi STX @ NASA/GSFC
	mod Aug.95 by F.V. to fix match of a single selected tag.
	mod Mar.97 by F.V. do not pass the SELECT_TAGS keyword in recursion,
		and check validity of INDEX_FROM and INDEX_TO in more detail.
	Converted to IDL V5.0   W. Landsman   September 1997
       Use long integers W. Landsman May 2001

(See $IDLUTILS_DIR/goddard/pro/structure/copy_struct_inx.pro)

CORREL_IMAGES

 NAME:
	CORREL_IMAGES
 PURPOSE:
       Compute the 2-D cross-correlation function of two images
 EXPLANATION:
       Computes the 2-D cross-correlation function of two images for
       a range of (x,y) shifting by pixels of one image relative to the other.

 CALLING SEQUENCE:
       Result = CORREL_IMAGES( image_A, image_B, 
                        [XSHIFT=, YSHIFT=, XOFFSET_B=, YOFFSET_B=, REDUCTION=, 
                        MAGNIFICATION=, /NUMPIX, /MONITOR  )

 INPUTS:
       image_A, image_B = the two images of interest.

 OPTIONAL INPUT KEYWORDS:
       XSHIFT = the + & - shift to be applied in X direction, default=7.
       YSHIFT = the Y direction + & - shifting, default=7.

       XOFFSET_B = initial X pixel offset of image_B relative to image_A.
       YOFFSET_B = Y pixel offset, defaults are (0,0).

       REDUCTION = optional reduction factor causes computation of
                       Low resolution correlation of bin averaged images,
                       thus faster. Can be used to get approximate optimal
                       (x,y) offset of images, and then called for successive
                       lower reductions in conjunction with CorrMat_Analyze
                       until REDUCTION=1, getting offset up to single pixel.

       MAGNIFICATION = option causes computation of high resolution correlation
                       of magnified images, thus much slower.
                       Shifting distance is automatically = 2 + Magnification,
                       and optimal pixel offset should be known and specified.
                       Optimal offset can then be found to fractional pixels
                       using CorrMat_Analyze( correl_images( ) ).

       /NUMPIX - if set, causes the number of pixels for each correlation
                       to be saved in a second image, concatenated to the
                       correlation image, so Result is fltarr( Nx, Ny, 2 ).
       /MONITOR causes the progress of computation to be briefly printed.

 OUTPUTS:
       Result is the cross-correlation function, given as a matrix.

 PROCEDURE:
       Loop over all possible (x,y) shifts, compute overlap and correlation
       for each shift. Correlation set to zero when there is no overlap.

 MODIFICATION HISTORY:
       Written, July,1991, Frank Varosi, STX @ NASA/GSFC
       Use ROUND instead of NINT, June 1995, Wayne Landsman HSTX
       Avoid divide by zero errors, W. Landsman HSTX April 1996
	Remove use of !DEBUG    W. Landsman   June 1997
       Subtract mean of entire image before computing correlation, not just 
          mean of overlap region   H. Ebeling/W. Landsman   June 1998
       Always REBIN() using floating pt arithmetic W. Landsman  Nov 2007

(See $IDLUTILS_DIR/goddard/pro/image/correl_images.pro)

CORREL_OPTIMIZE

 NAME:
	CORREL_OPTIMIZE

 PURPOSE:
	Find the optimal (x,y) pixel offset of image_B relative to image_A
 EXPLANATION"
	Optimal offset is computed by means of maximizing the correlation 
	function of the two images.

 CALLING SEQUENCE:
	CORREL_OPTIMIZE, image_A, image_B, xoffset_optimum, yoffset_optimum 
		[ XOFF_INIT=, YOFF_INIT=, MAGNIFICATION=, /PRINT, /NUMPIX, 
		  /MONITOR, PLATEAU_THRESH=  ]

 INPUTS:
	image_A, image_B = the two images of interest.

 OPTIONAL INPUT KEYWORDS:
	XOFF_INIT = initial X pixel offset of image_B relative to image_A,
	YOFF_INIT = Y pixel offset, (default offsets are 0 and 0).
	MAGNIFICATION = option to determine offsets up to fractional pixels,
			(example: MAG=2 means 1/2 pixel accuracy, default=1).
	/NUMPIX: sqrt( sqrt( # pixels )) used as correlation weighting factor.
	/MONITOR causes the progress of computation to be briefly printed.
	/PRINT causes the results of analysis to be printed.
	PLATEAU_THRESH = threshold used for detecting plateaus in 
		the cross-correlation matrix near maximum, (default=0.01),
		used only if MAGNIFICATION > 1.    Decrease this value for
		high signal-to-noise data

 OUTPUTS:
	xoffset_optimum = optimal X pixel offset of image_B relative to image_A.
	yoffset_optimum = optimal Y pixel offset.

 CALLS:
	function  correl_images( image_A, image_B )
	pro  corrmat_analyze

 PROCEDURE:
	The combination of function correl_images( image_A, image_B ) and
	corrmat_analyze of the result is used to obtain the (x,y) offset
	yielding maximal correlation. The combination is first executed at
	large REDUCTION factors to speed up computation, then zooming in 
	recursively on the optimal (x,y) offset by factors of 2.
	Finally, the MAGNIFICATION option (if specified)
	is executed to determine the (x,y) offset up to fractional pixels.
	
 MODIFICATION HISTORY:
	Written, July,1991, Frank Varosi, STX @ NASA/GSFC
	Added PLATEAU_THRESH keyword  June 1997,  Wayne Landsman  STX   
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/image/correl_optimize.pro)

CORRMAT_ANALYZE

 NAME:
	CORRMAT_ANALYZE 
 PURPOSE:
	Find the optimal (x,y) offset to maximize correlation of 2 images
 EXPLANATION:
	Analyzes the 2-D cross-correlation function of two images
	and finds the optimal(x,y) pixel offsets.
	Intended for use with function CORREL_IMAGES.

 CALLING SEQUENCE:
	corrmat_analyze, correl_mat, xoffset_optimum, yoffset_optimum, 
		max_corr, edge, plateau, [XOFF_INIT=, YOFF_INIT=, REDUCTION=, 
		MAGNIFICATION=, PLATEAU_THRESH=, /PRINT]

 INPUTS:
	correl_mat = the cross-correlation matrix of 2 images.
			(as computed by function CORREL_IMAGES( imA, imB ) ).

 NOTE:
	If correl_mat(*,*,1) is the number of pixels for each correlation,
	(the case when /NUMPIX was specified in call to CORREL_IMAGES)
	then sqrt( sqrt( # pixels )) is used as correlation weighting factor.

 OPTIONAL INPUT KEYWORDS:
	XOFF_INIT = initial X pixel offset of image_B relative to image_A.
	YOFF_INIT = Y pixel offset, (both as specified to correl_images).
	REDUCTION = reduction factor used in call to CORREL_IMAGES.
	MAGNIFICATION = magnification factor used in call to CORREL_IMAGES,
		this allows determination of offsets up to fractions of a pixel.
	PLATEAU_THRESH = threshold used for detecting plateaus in 
		the cross-correlation matrix near maximum, (default=0.01),
		used only if MAGNIFICATION > 1
	/PRINT causes the result of analysis to be printed.

 OUTPUTS:
	xoffset_optimum = optimal X pixel offset of image_B relative to image_A.
	yoffset_optimum = optimal Y pixel offset.
	max_corr = the maximal correlation corresponding to optimal offset.
	edge = 1 if maximum is at edge of correlation domain, otherwise=0.
	plateau = 1 if maximum is in a plateua of correlation function, else=0.

 PROCEDURE:
	Find point of maximum cross-correlation and calc. corresponding offsets.
	If MAGNIFICATION > 1:
	the  correl_mat is checked for plateau near maximum, and if found,
	the center of plateau is taken as point of maximum cross-correlation.

 MODIFICATION HISTORY:
	Written, July-1991, Frank Varosi, STX @ NASA/GSFC
	Use ROUND instead of NINT, June 1995 Wayne Landsman HSTX
	Remove use of non-standard !DEBUG system variable   W.L. HSTX 
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/image/corrmat_analyze.pro)

COSMO_PARAM

 NAME:
     COSMO_PARAM
 PURPOSE:
     Derive full set of cosmological density parameters from a partial set
 EXPLANATION:
     This procedure is called by LUMDIST and GALAGE to allow the user a choice
     in defining any two of four cosmological density parameters.

     Given any two of the four input parameters -- (1) the normalized matter 
     density Omega_m (2) the normalized cosmological constant, Omega_lambda 
     (3) the normalized curvature term, Omega_k and (4) the deceleration 
     parameter q0 --  this  program will derive the remaining two.     Here 
     "normalized" means divided by the closure density so that 
     Omega_m + Omega_lambda + Omega_k = 1.    For a more
     precise definition see Carroll, Press, & Turner (1992, ArAA, 30, 499).     

     If less than two parameters are defined, this procedure sets default 
     values of Omega_k=0 (flat space), Omega_lambda = 0.7, Omega_m = 0.3
     and q0 = -0.55
 CALLING SEQUENCE:
       COSMO_PARAM, Omega_m, Omega_lambda, Omega_k, q0

 INPUT-OUTPUTS:
     Omega_M - normalized matter energy density, non-negative numeric scalar
     Omega_Lambda - Normalized cosmological constant, numeric scalar
     Omega_k - normalized curvature parameter, numeric scalar.   This is zero
               for a flat universe
     q0 - Deceleration parameter, numeric scalar = -R*(R'')/(R')^2
          = 0.5*Omega_m - Omega_lambda
 NOTES:
     If more than two parameters are defined upon input (overspecification), 
     then the first two defined parameters in the ordered list Omega_m, 
     Omega_lambda, Omega_k, q0 are used to define the cosmology.
 EXAMPLE:
     Suppose one has Omega_m = 0.3, and Omega_k = 0.5 then to determine
     Omega_lambda and q0
    
       IDL> cosmo_param, 0.3, omega_lambda, 0.5, q0
   
       which will return omega_lambda = 0.2 and q0 = -2.45
 REVISION HISTORY:
       W. Landsman         Raytheon ITSS         April 2000
       Better Error checking  W. Landsman/D. Syphers   October 2010

(See $IDLUTILS_DIR/goddard/pro/astro/cosmo_param.pro)

COYOTEGRAPHIC

   This simple just identifies a routine as a Coyote Graphic routine. It is written
   primarily so I can identify such routines before I assign a background color to
   a graphics window.

 :Categories:
    Graphics
    
 :Examples:
    Used in graphics programs::
       IDL> IF CoyoteGraphic() THEN background = 'white'
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 18 January 2011. DWF.      

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/coyotegraphic.pro)

CO_ABERRATION

  NAME:
     CO_ABERRATION
 PURPOSE:
     Calculate changes to Ra and Dec due to "the effect of aberration", 
 EXPLANATION:
      as described in Meeus, Chap 23.
 CALLING SEQUENCE:
      co_aberration, jd, ra, dec, d_ra, d_dec, [EPS = ]
 INPUTS
       jd      : Julian Date [scalar or vector]
       ra, dec : Arrays (or scalars) of the ra  and dec's in degrees
   Note: if jd is a vector, ra and dec MUST be vectors of the same length.

 OUTPUTS
       d_ra, d_dec: the corrections to ra and dec due to aberration (must then
                     be added to ra and dec to get corrected values).
 OPTIONAL INPUT KEYWORD:
       eps : set this to the true obliquity of the ecliptic (in radians), or
         it will be set for you if you don't know it (in that case, set it to
                 an empty variable).
 EXAMPLE:
   Compute the change in RA and Dec of Theta Persei (RA = 2h46m,11.331s, Dec =
   49d20',54.54" on 2028 Nov 13.19 TD

      IDL> jdcnv,2028,11,13,.19*24,jd      ;Get Julian date
      IDL> co_aberration,jd,ten(2,46,11.331)*15,ten(49,20,54.54),d_ra,d_dec

      ==> d_ra = 30.045"    d_dec = 6.697"
 NOTES:
  These formula are from Meeus, Chapters 23.  Accuracy is much better than 1 
   arcsecond.

 REVISION HISTORY:
   Written, June 2002,      Chris O'Dell, U. of Wisconsin
   Fix error with vector input   W. Landsman   June 2009

(See $IDLUTILS_DIR/goddard/pro/astro/co_aberration.pro)

CO_NUTATE

  NAME:
     CO_NUTATE
  PURPOSE:
     Calculate changes in RA and Dec due to nutation of the Earth's rotation
 EXPLANATION:
     Calculates necessary changes to ra and dec due to
     the nutation of the Earth's rotation axis, as described in Meeus, Chap 23.
     Uses formulae from Astronomical Almanac, 1984, and does the calculations
     in equatorial rectangular coordinates to avoid singularities at the
     celestial poles.

 CALLING SEQUENCE:
     CO_NUTATE, jd, ra, dec, d_ra, d_dec, [EPS=, D_PSI =, D_EPS = ]
 INPUTS
    JD: Julian Date [scalar or vector]
    RA, DEC : Arrays (or scalars) of the ra and dec's of interest

   Note: if jd is a vector, ra and dec MUST be vectors of the same length.

 OUTPUTS:
    d_ra, d_dec: the corrections to ra and dec due to nutation (must then
                                be added to ra and dec to get corrected values).
 OPTIONAL OUTPUT KEYWORDS:
    EPS: set this to a named variable that will contain the obliquity of the 
             ecliptic.
    D_PSI: set this to a named variable that will contain the nutation in the
           longitude of the ecliptic
    D_EPS: set this to a named variable that will contain the nutation in the
                       obliquity of the ecliptic
 EXAMPLE:
    (1) Example 23a in Meeus: On 2028 Nov 13.19 TD the mean position of Theta
        Persei is 2h 46m 11.331s 49d 20' 54.54".    Determine the shift in 
        position due to the Earth's nutation.
    
        IDL> jd = JULDAY(11,13,2028,.19*24)       ;Get Julian date
        IDL> CO_NUTATE, jd,ten(2,46,11.331)*15.,ten(49,20,54.54),d_ra,d_dec    

              ====> d_ra = 15.843"   d_dec = 6.217"
 PROCEDURES USED:
    NUTATE 
 REVISION HISTORY:
    Written  Chris O'Dell, 2002
    Vector call to NUTATE   W. Landsman   June 2002

(See $IDLUTILS_DIR/goddard/pro/astro/co_nutate.pro)

CO_REFRACT()

 NAME:
   CO_REFRACT()      

 PURPOSE:
   Calculate correction to altitude due to atmospheric refraction.

 DESCRIPTION:
   CO_REFRACT can calculate both apparent altitude from observed altitude and 
   vice-versa.

 CALLING SEQUENCE:
   new_alt  = CO_REFRACT(old_alt, [ ALTITUDE= , PRESSURE= , $
                                  TEMPERATURE= , /TO_OBSERVED , EPSILON= ])

 INPUT:
   old_alt - Observed (apparent) altitude, in DEGREES.  (apparent if keyword 
             /TO_OBSERVED set).    May be scalar or vector.

 OUTPUT: 
     Function returns apparent (observed) altitude, in DEGREES. (observed if 
         keyword /TO_OBSERVED set).    Will be of same type as input 
         altitude(s).

 OPTIONAL KEYWORD INPUTS:
      ALTITUDE :  The height of the observing location, in meters.  This is 
             only used to determine an approximate temperature and pressure, 
             if these are not specified separately. [default=0, i.e. sea level]
      PRESSURE :  The pressure at the observing location, in millibars.
      TEMPERATURE:    The temperature at the observing location, in Kelvin.
      EPSILON:  When keyword /TO_OBSERVED has been set, this is the accuracy 
               to  obtain via the iteration, in arcseconds [default = 0.25 
                arcseconds].
      /TO_OBSERVED:  Set this keyword to go from Apparent->Observed altitude, 
                 using the iterative technique.

       Note, if altitude is set, but temperature or pressure are not, the 
       program will make an intelligent guess for the temperature and pressure.

 DESCRIPTION:

   Because the index of refraction of air is not precisely 1.0, the atmosphere
   bends all incoming light, making a star or other celestial object appear at
   a slightly different altitude (or elevation) than it really is.  It is 
   important to understand the following definitions:

   Observed Altitude:  The altitude that a star is SEEN to BE, with a telescope.
                       This is where it appears in the sky.  This is always 
                       GREATER than the apparent altitude.

   Apparent Altitude:  The altitude that a star would be at, if *there were no
                     atmosphere* (sometimes called "true" altitude). This is 
                     usually calculated from an object's celestial coordinates.
                     Apparent altitude is always LOWER than the observed 
                     altitude.

   Thus, for example, the Sun's apparent altitude when you see it right on the
   horizon is actually -34 arcminutes.

   This program uses couple simple formulae to estimate the effect for most 
   optical and radio wavelengths.  Typically, you know your observed altitude 
   (from an observation), and want the apparent altitude.  To go the other way,
   this program uses an iterative approach.

 EXAMPLE:
    The lower limb of the Sun is observed to have altitude of 0d 30'.   
    Calculate the the true (=apparent) altitude of the Sun's lower limb using 
    mean  conditions of air pressure and temperature

    IDL> print, co_refract(0.5)     ===>  0.025degrees (1.55')
 WAVELENGTH DEPENDENCE:
    This correction is 0 at zenith, about 1 arcminute at 45 degrees, and 34 
    arcminutes at the horizon FOR OPTICAL WAVELENGTHS.  The correction is 
    NON-NEGLIGIBLE at all wavelengths, but is not very easily calculable.  
    These formulae assume a wavelength of 550 nm, and will be accurate to 
    about 4 arcseconds for all visible wavelengths, for elevations of 10 
    degrees and higher.    Amazingly, they are also ACCURATE FOR RADIO 
    FREQUENCIES LESS THAN ~ 100 GHz.

    It is important to understand that these formulae really can't do better 
    than about 30 arcseconds of accuracy very close to the horizon, as 
    variable atmospheric effects become very important.

 REFERENCES:
    1.  Meeus, Astronomical Algorithms, Chapter 15.
    2.  Explanatory Supplement to the Astronomical Almanac, 1992.
    3.  Methods of Experimental Physics, Vol 12 Part B, Astrophysics, 
        Radio Telescopes, Chapter 2.5, "Refraction Effects in the Neutral 
        Atmosphere", by R.K. Crane.


 DEPENDENCIES:
    CO_REFRACT_FORWARD (contained in this file and automatically compiled).

 AUTHOR:
   Chris O'Dell
       Univ. of Wisconsin-Madison
   Observational Cosmology Laboratory
   Email: odell@cmb.physics.wisc.edu

 REVISION HISTORY:
    version 1 (May 31, 2002)
    Update iteration formula,   W. Landsman    June 2002
    Corrected slight bug associated with scalar vs. vector temperature and 
               pressure inputs. 6/10/2002
    Fixed problem with vector input when /TO_OBSERVED set W. Landsman Dec 2005
    Allow arrays with more than 32767 elements W.Landsman/C.Dickinson Feb 2010

(See $IDLUTILS_DIR/goddard/pro/astro/co_refract.pro)

CREATE_STRUCT

 NAME:
       CREATE_STRUCT
 PURPOSE:
       Create an IDL structure from a list of tag names and dimensions
 EXPLANATION:
       Dynamically create an IDL structure variable from list of tag names 
       and data types of arbitrary dimensions.   Useful when the type of
       structure needed is not known until run time.

       Unlike the intrinsic function CREATE_STRUCT(), this procedure does not
       require the user to know the number of tags before run time.   (Note
       there is no name conflict since the intrinsic CREATE_STRUCT is a 
       function, and this file contains a procedure.)
 CALLING SEQUENCE:
       CREATE_STRUCT, STRUCT, strname, tagnames, tag_descript, 
                             [ DIMEN = , /CHATTER, /NODELETE ]

 INPUTS:
       STRNAME -   name to be associated with structure (string)
               Must be unique for each structure created.   Set
               STRNAME = '' to create an anonymous structure

       TAGNAMES -  tag names for structure elements (string or string array)
                Any strings that are not valid IDL tag names (e.g. 'a\2')
                will be converted by IDL_VALIDNAME to a valid tagname by 
                replacing with underscores as necessary (e.g. 'a_2')

       TAG_DESCRIPT -  String descriptor for the structure, containing the
               tag type and dimensions.  For example, 'A(2),F(3),I', would
               be the descriptor for a structure with 3 tags, strarr(2), 
               fltarr(3) and Integer scalar, respectively.
               Allowed types are 'A' for strings, 'B' or 'L' for unsigned byte 
               integers, 'I' for integers, 'J' for longword integers, 
               'K' for 64bit integers, 'F' or 'E' for floating point, 
               'D' for double precision  'C' for complex, and 'M' for double 
               complex.   Uninterpretable characters in a format field are 
               ignored.

               For vectors, the tag description can also be specified by
               a repeat count.  For example, '16E,2J' would specify a 
               structure with two tags, fltarr(16), and lonarr(2)

 OPTIONAL KEYWORD INPUTS:
       DIMEN -    number of dimensions of structure array (default is 1)

       CHATTER -  If set, then CREATE_STRUCT() will display
                  the dimensions of the structure to be created, and prompt
                  the user whether to continue.  Default is no prompt.

       /NODELETE - If set, then the temporary file created
                  CREATE_STRUCT will not be deleted upon exiting.   See below

 OUTPUTS:
       STRUCT -   IDL structure, created according to specifications 

 EXAMPLES: 

       IDL> create_struct, new, 'name',['tag1','tag2','tag3'], 'D(2),F,A(1)'

       will create a structure variable new, with structure name NAME

       To see the structure of new:

       IDL> help,new,/struc
       ** Structure NAME, 3 tags, 20 length:
          TAG1            DOUBLE         Array(2)
          TAG2            FLOAT          0.0
          TAG3            STRING         Array(1)

 PROCEDURE:
       Generates a temporary procedure file using input information with
       the desired structure data types and dimensions hard-coded.
       This file is then executed with CALL_PROCEDURE.

 NOTES:
       If CREATE_STRUCT cannot write a temporary .pro file in the current 
       directory, then it will write the temporary file in the getenv('HOME')
       directory.

       Note that 'L' now specifies a LOGICAL (byte) data type and not a
       a LONG data type for consistency with FITS binary tables

 RESTRICTIONS:
       The name of the structure must be unique, for each structure created.
       Otherwise, the new variable will have the same structure as the 
       previous definition (because the temporary procedure will not be
       recompiled).  ** No error message will be generated  ***

 SUBROUTINES CALLED:
       REPCHR() 

 MODIFICATION HISTORY:
       Version 1.0 RAS January 1992
       Modified 26 Feb 1992 for Rosat IDL Library (GAR)
       Modified Jun 1992 to accept arrays for tag elements -- KLV, Hughes STX
       Accept anonymous structures W. Landsman  HSTX    Sep. 92
       Accept 'E' and 'J' format specifications   W. Landsman Jan 93
       'L' format now stands for logical and not long array
       Accept repeat format for vectors        W. Landsman Feb 93
       Accept complex and double complex (for V4.0)   W. Landsman Jul 95
       Work for long structure definitions  W. Landsman Aug 97
       Write temporary file in HOME directory if necessary  W. Landsman Jul 98
       Use OPENR,/DELETE for OS-independent file removal W. Landsman Jan 99
       Use STRSPLIT() instead of GETTOK() W. Landsman  July 2002
       Assume since V5.3 W. Landsman  Feb 2004
       Added RESOLVE_ROUTINE to ensure recompilation W. Landsman Sep. 2004
       Delete temporary with FILE_DELETE   W. Landsman Sep 2006
       Assume since V5.5, delete VMS reference  W.Landsman Sep 2006
       Added 'K' format for 64 bit integers, IDL_VALIDNAME check on tags
                       W. Landsman  Feb 2007
       Use vector form of IDL_VALIDNAME() if V6.4 or later W.L. Dec 2007
       Suppress compilation mesage of temporary file A. Conley/W.L. May 2009
       Remove FDECOMP, some cleaner coding  W.L. July 2009
       Do not limit string length to 1000 chars   P. Broos,  Feb 2011

(See $IDLUTILS_DIR/goddard/pro/structure/create_struct.pro)

CR_REJECT

 NAME:
     CR_REJECT

 PURPOSE:
     General, iterative cosmic ray rejection using two or more input images.

 EXPLANATION:
     Uses a noise model input by the user, rather than
     determining noise empirically from the images themselves.

     The image returned has the combined exposure time of all the input
     images, unless the bias flag is set, in which case the mean is
     returned.  This image is computed by summation (or taking mean)
     regardless of loop and initialization options (see below).

 CALLING SEQUENCE:
     cr_reject, input_cube, rd_noise_dn, dark_dn, gain, mult_noise, $
        combined_image, combined_npix, combined_noise

 MODIFIED ARGUMENT:
     input_cube - Cube in which each plane is an input image.
                  If the noise model is used (rd_noise_dn, dark_dn,
                  gain), then input_cube must be in units of DN.
                  If an input noise cube is supplied (rd_noise_dn
                  <0), then the units of input_cube and noise_cube
                  merely need to be consistent.  

                  This array is used as a buffer and its contents 
                  are not guaranteed on output (although for now, 
                  weighting=0 with /restore_sky should give you back 
                  your input unaltered).

 INPUT ARGUMENTS:
     rd_noise_dn - Read noise per pixel.  Units are DN.
                   If negative, then the user supplies an error cube
                   via the keyword noise_cube.  In the latter case,
                   mult_noise still applies, since it is basically a fudge.
     dark_dn     - Dark rate in DN per pixel per s.  This can be a scalar,
                   or it can be a dark image divided by the exposure
                   time.
     gain        - Electrons per DN.
     mult_noise  - Coefficient for multiplicative noise term -- helps
                   account for differing PSFs or subpixel image shifts.

 INPUT KEYWORDS:
     exptime    - If the images have different exposure times, pass
                  them in a vector.  You can leave this off for 
                  frames with the same exposure time, but dark counts
                  won't be treated correctly.
     verbose    - If set, lots of output.
     nsig       - Rejection limit in units of pixel-to-pixel noise
                  (sigma) on each input image.  Can be specified as
                  an array, in which case the dimension gives the
                  maximum number of iterations to run.  (Default = 
                  [8, 6, 4]
     dilation   - With dfactor, provides functionality similar to the
                  expansion of the CR with pfactor and radius in STSDAS 
                  crrej.  Dilate gives the size of the border to be
                  tested around each initially detected CR pixel.
                  E.g., dilate=1 searches a 9 X 9 area centered on the
                  original pixel.  If dfactor is set, the default is 1.
     dfactor    - See dilation.  This parameter is equivalent to pfactor
                  in STSDAS crrej.  The current threshold for rejection
                  is multiplied by this factor when doing the search
                  with the dilated mask.  If dilation is set, the default
                  for this parameter is 0.5.
     bias       - Set if combining biases (divides through by number
                  of images at end, since exposure time is 0).
     tracking_set - Subscripts of pixels to be followed through the 
                    computation.
     noskyadjust  - Sky not to be subtracted before rejection tests.  Default
                  is to do the subtraction.
     xmedsky    - Flag.  If set, the sky is computed as a 1-d array
                  which is a column-by-column median.  This is intended
                  for STIS slitless spectra.  If sky adjustment is
                  disabled, this keyword has no effect.
     input_mask - Mask cube input by the user.  Should be byte data
                  because it's boolean.  1 means use the pixel,
                  and 0 means reject the pixel - these rejections
                  are in addition to those done by the CR rejection
                  algorithm as such.

     The following keywords control how the current guess at a CR-free
     "check image" is recomputed on each iteration:

     median_loop  - If set, the check image for each iteration is
                    the pixel-by-pixel median. THE MEAN IS
                    RETURNED in combined_image even if you set
                    this option.  (Default is mean_loop.)
     minimum_loop - If set, the check image for each iteration is
                    the pixel-by-pixel minimum. THE MEAN IS
                    RETURNED in combined_image even if you set
                    this option.  (Default is mean_loop.)
     mean_loop    - If set, the check image for each iteration is
                    the pixel-by-pixel mean.  (Same as the default.)
     noclearmask  - By default, the mask of CR flags is reset before
                    every iteration, and a pixel that has been
                    rejected has a chance to get back in the game
                    if the average migrates toward its value.  If this
                    keyword is set, then any rejected pixel stays 
                    rejected in subsequent iterations.  Note that what 
                    stsdas.hst_calib.wfpc.crrej does is the same
                    as the default.  For this procedure, the default
                    was NOT to clear the flags, until 20 Oct. 1997.
     restore_sky  - Flag.  If set, the routine adds the sky back into
                    input_cube before returning.  Works only if
                    weighting=0.
     null_value   - Value to be used for output pixels to which no
                    input pixels contribute.  Default=0
     weighting    - Selects weighting scheme in final image
                    combination:
                     0 (default) - Poissonian weighting - co-add
                         detected DN from non-CR pixels.  (Pixel-by-
                         pixel scaling up to total exposure time,
                         for pixels in stack where some rejected.)
                         Equivalent to exptime weighting of rates.
                     1 or more - Sky and read noise weighting of rates.
                         Computed as weighted average of DN rates,
                         with total exp time multiplied back in
                         afterward.

                    In all cases, the image is returned as a sum in
                    DN with the total exposure time of the image 
                    stack, and with total sky added back in.

     The following keywords allow the initial guess at a CR-free "check
     image" to be of a different kind from the iterative guesses:

     init_med  - If set, the initial check image is
                 the pixel-by-pixel median.  (Not permitted if
                 input_cube has fewer than 3 planes; default is minimum.)
     init_mean - If set, the initial check image is
                 the pixel-by-pixel mean.  (Default is minimum.)    
     init_min  - If set, the initial check image is
                 the pixel-by-pixel minimum.  (Same as the default.)    
  
 OUTPUT ARGUMENTS::
     combined_image - Mean image with CRs removed.
     combined_npix  - Byte (or integer) image of same dimensions as
                      combined_image, with each element containing
                      the number of non-CR stacked pixels that
                      went into the  result.
     combined_noise - Noise in combined image according to noise model
                      or supplied noise cube.

 OUTPUT KEYWORDS:
     mask_cube      - CR masks for each input image.  1 means
                      good pixel; 0 means CR pixel.
     skyvals        - Sky value array.  For an image cube with N planes,
                      this array is fltarr(N) if the sky is a scalar per
                      image plane, and fltarr(XDIM, N), is the XMEDSKY
                      is set.

 INPUT/OUTPUT KEYWORD:
     noise_cube     - Estimated noise in each pixel of input_cube as
                      returned (if rd_noise_dn ge 0), or input noise
                      per pixel of image_cube (if rd_noise_dn lt 0).
     skybox         - X0, X1, Y0, Y1 bounds of image section used
                      to compute sky.  If supplied by user, this 
                      region is used.  If not supplied, the
                      image bounds are returned.  This parameter might
                      be used (for instance) if the imaging area
                      doesn't include the whole chip.

 COMMON BLOCKS:  none

 SIDE EFFECTS:  none

 METHOD: 
     
     COMPARISON WITH STSDAS

     Cr_reject emulates the crrej routine in stsdas.hst_calib.wfpc.
     The two routines have been verified to give identical results
     (except for some pixels along the edge of the image) under the 
     following conditions:

          no sky adjustment
          no dilation of CRs
          initialization of trial image with minimum
          taking mean for each trial image after first (no choice
             in crrej)
     
     Dilation introduces a difference between crrej and this routine
     around the very edge of the image, because the IDL mask
     manipulation routines don't handle the edge the same way as crrej
     does.  Away from the edge, crrej and cr_reject are the same with
     respect to dilation.

     The main difference between crrej and cr_reject is in the sky
     computation.  Cr_reject does a DAOPHOT I sky computation on a 
     subset of pixels grabbed from the image, whereas crrej searches
     for a histogram mode.

     REMARKS ON USAGE

     The default is that the initial guess at a CR-free image is the
     pixel-by-pixel minimum of all the input images.  The pixels
     cut from each component image are the ones more than nsig(0) sigma
     from this minimum image.  The next iteration is based on the
     mean of the cleaned-up component images, and the cut is taken
     at nsig(1) sigma.  The next iteration is also based on the mean with
     the cut taken at nsig(2) sigma.

     The user can specify an arbitrary sequence of sigma cuts, e.g.,
     nsig=[6,2] or nsig=[10,9,8,7].  The user can also specify that
     the initial guess is the median (/init_med) rather than the
     minimum, or even the mean.  The iterated cleaned_up images after
     the first guess can be computed as the mean or the median
     (/mean_loop or /median_loop).  The minimum_loop option is also
     specified, but this is a trivial case, and you wouldn't want
     to use it except perhaps for testing.

     The routine takes into account exposure time if you want it to, 
     i.e., if the pieces of the CR-split aren't exactly the same.
     For bias frames (exposure time 0), set /bias to return the mean
     rather than the total of the cleaned-up component images.

     The crrej pfactor and radius to propagate the detected CRs
     outward from their initial locations have been implemented
     in slightly different form using the IDL DILATE function.

     It is possible to end up with output pixels to which no valid
     input pixels contribute.  These end up with the value
     NULL_VALUE, and the corresponding pixels of combined_npix are
     also returned as 0.  This result can occur when the pixel is
     very noisy across the whole image stack, i.e., if all the
     values are, at any step of the process, far from the stack
     average at that position even after rejecting the real
     outliers.  Because  pixels are flagged symmetrically N sigma
     above and below the  current combined image (see code), all
     the pixels at a given  position can end up getting flagged.
     (At least, that's how I think it happens.)

 MODIFICATION HISTORY:
      5 Mar. 1997 - Written.  R. S. Hill
     14 Mar. 1997 - Changed to masking approach to keep better
                    statistics and return CR-affected pixels to user.
                    Option to track subset of pixels added.
                    Dilation of initially detected CRs added.
                    Other small changes.  RSH
     17 Mar. 1997 - Arglist and treatment of exposure times fiddled
                    to mesh better with stis_cr.  RSH
     25 Mar. 1997 - Fixed bug if dilation finds nothing.  RSH
      4 Apr. 1997 - Changed name to cr_reject.  RSH
     15 Apr. 1997 - Restyled with emacs, nothing else done.  RSH
     18 Jun. 1997 - Input noise cube allowed.  RSH
     19 Jun. 1997 - Multiplicative noise deleted from final error.  RSH
     20 Jun. 1997 - Fixed error in using input noise cube.  RSH
     12 July 1997 - Sky adjustment option.  RSH
     27 Aug. 1997 - Dilation kernel made round, not square, and
                    floating-point radius allowed.  RSH
     16 Sep. 1997 - Clearmask added.  Intermediate as well as final
                    mean is exptime weighted.  RSH
     17 Sep. 1997 - Redundant zeroes around dilation kernel trimmed.  RSH
      1 Oct. 1997 - Bugfix in preceding.  RSH
     21 Oct. 1997 - Clearmask changed to noclearmask.  Bug in robust
                    array division fixed (misplaced parens).  Sky as
                    a function of X (option).  RSH
     30 Jan. 1998 - Restore_sky keyword added.  RSH
      5 Feb. 1998 - Quick help corrected and updated.  RSH
      6 Feb. 1998 - Fixed bug in execution sequence for tracking_set 
                    option.  RSH
     18 Mar. 1998 - Eliminated confusing maxiter spec.  Added
                    null_value keyword.  RSH
     15 May  1998 - Input_mask keyword.  RSH
     27 May  1998 - Initialization of minimum image corrected. NRC, RSH
      9 June 1998 - Input mask cube processing corrected.  RSH
     21 Sep. 1998 - Weighting keyword added.  RSH
      7 Oct. 1998 - Fixed bug in input_mask processing (introduced
                    in preceding update).  Input_mask passed to
                    skyadj_cube.  RSH
      5 Mar. 1999 - Force init_min for 2 planes.  RSH
      1 Oct. 1999 - Make sure weighting=1 not given with noise cube.  RSH
      1 Dec. 1999 - Corrections to doc; restore_sky needs weighting=0.  RSH
     17 Mar. 2000 - SKYBOX added.  RSH

(See $IDLUTILS_DIR/goddard/pro/image/cr_reject.pro)

CSPLINE

 NAME:
      CSPLINE

 PURPOSE:
      Function to evaluate a natural cubic spline at specified data points
 EXPLANATION:
      Combines the Numerical Recipes functions SPL_INIT and SPL_INTERP

 CALLING SEQUENCE:
      result = cspline( x, y, t, [ DERIV = ])

 INPUTS:
      x - vector of spline node positions, must be monotonic increasing or
          decreasing
      y - vector of node values
      t - x-positions at which to evaluate the spline, scalar or vector

 INPUT-OUTPUT KEYWORD:
      DERIV - values of the second derivatives of the interpolating function 
               at the node points.   This is an intermediate step in the 
               computation of the natural spline that requires only the X and 
               Y vectors.    If repeated interpolation is to be applied to 
               the same (X,Y) pair, then some computation time can be saved 
               by supplying the DERIV keyword on each call.   On the first call
               DERIV will be computed and returned on output.    

 OUTPUT:
       the values for positions t are returned as the function value
       If any of the input variables are double precision, then the output will
       also be double precision; otherwise the output is floating point.

 EXAMPLE:                               
       The following uses the example vectors from the SPL_INTERP documentation

       IDL> x = (findgen(21)/20.0)*2.0*!PI ;X vector
       IDL> y = sin(x)                     ;Y vector
       IDL> t = (findgen(11)/11.0)*!PI     ;Values at which to interpolate 
       IDL> cgplot,x,y,psym=1                ;Plot original grid
       IDL> cgplot, /over, t,cspline(x,y,t),psym=2 ;Overplot interpolated values

 METHOD:
      The "Numerical Recipes" implementation of the natural cubic spline is 
      used, by calling the intrinsic IDL functions SPL_INIT and SPL_INTERP.

 HISTORY:
      version 1  D. Lindler  May, 1989
      version 2  W. Landsman April, 1997
      Rewrite using the intrinsic SPL_INIT & SPL_INTERP functions
      Converted to IDL V5.0   W. Landsman   September 1997
      Work for monotonic decreasing X vector    W. Landsman   February 1999

(See $IDLUTILS_DIR/goddard/pro/math/cspline.pro)

CT2LST

 NAME:
     CT2LST
 PURPOSE:
     To convert from Local Civil Time to Local Mean Sidereal Time.

 CALLING SEQUENCE:
     CT2LST, Lst, Lng, Tz, Time, [Day, Mon, Year] 
                       or
     CT2LST, Lst, Lng, dummy, JD

 INPUTS:
     Lng  - The longitude in degrees (east of Greenwich) of the place for 
            which the local sidereal time is desired, scalar.   The Greenwich 
            mean sidereal time (GMST) can be found by setting Lng = 0.
     Tz  - The time zone of the site in hours, positive East  of the Greenwich
           meridian (ahead of GMT).  Use this parameter to easily account 
           for Daylight Savings time (e.g. -4=EDT, -5 = EST/CDT), scalar
           This parameter is not needed (and ignored) if Julian date is 
           supplied.    ***Note that the sign of TZ was changed in July 2008
           to match the standard definition.*** 
     Time or JD  - If more than four parameters are specified, then this is 
               the time of day of the specified date in decimal hours.  If 
               exactly four parameters are specified, then this is the 
               Julian date of time in question, scalar or vector

 OPTIONAL INPUTS:
      Day -  The day of the month (1-31),integer scalar or vector
      Mon -  The month, in numerical format (1-12), integer scalar or vector
      Year - The 4 digit year (e.g. 2008), integer scalar or vector

 OUTPUTS:
       Lst   The Local Sidereal Time for the date/time specified in hours.

 RESTRICTIONS:
       If specified, the date should be in numerical form.  The year should
       appear as yyyy.

 PROCEDURE:
       The Julian date of the day and time is question is used to determine
       the number of days to have passed since 0 Jan 2000.  This is used
       in conjunction with the GST of that date to extrapolate to the current
       GST; this is then used to get the LST.    See Astronomical Algorithms
       by Jean Meeus, p. 84 (Eq. 11-4) for the constants used.

 EXAMPLE:
       Find the Greenwich mean sidereal time (GMST) on 2008 Jul 30 at 15:53 pm
       in Baltimore, Maryland (longitude=-76.72 degrees).   The timezone is 
       EDT or tz=-4

       IDL> CT2LST, lst, -76.72, -4,ten(15,53), 30, 07, 2008

               ==> lst =  11.356505  hours  (= 11h 21m 23.418s)

       The Web site  http://tycho.usno.navy.mil/sidereal.html contains more
       info on sidereal time, as well as an interactive calculator.
 PROCEDURES USED:
       jdcnv - Convert from year, month, day, hour to julian date

 MODIFICATION HISTORY:
     Adapted from the FORTRAN program GETSD by Michael R. Greason, STX, 
               27 October 1988.
     Use IAU 1984 constants Wayne Landsman, HSTX, April 1995, results 
               differ by about 0.1 seconds  
     Longitudes measured *east* of Greenwich   W. Landsman    December 1998
     Time zone now measure positive East of Greenwich W. Landsman July 2008
     Remove debugging print statement  W. Landsman April 2009

(See $IDLUTILS_DIR/goddard/pro/astro/ct2lst.pro)

CURS

 NAME:
       CURS
 PURPOSE:
       Selects an X windows cursor shape
 CALLING SEQUENCE:
       curs            ;Interactively select a cursor shape.
       curs, sel       ;Make the given CURSOR_STANDARD value the cursor
                        shape.
 OPTIONAL INPUT:
       sel  -  Either an integer giving the CURSOR_STANDARD value (usually an 
               even value between 0 and 152) indicating the cursor shape, or 
               a string from the following menu
       a -- Up arrow              
       b -- Left-angled arrow
       c -- Right-angled arrow
       d -- Crosshair
       e -- Finger pointing left 
       f -- Finger pointing right
       g -- Narrow crosshair
       h -- Cycle through all possible standard cursor shapes
 
       The full list of available cursor values is given in 
      /usr/include/X11/cursorfont.h
 OUTPUTS:
       None.
 RESTRICTIONS:
       Uses the CURSOR_STANDARD keyword of the DEVICE procedure.  Although 
       this keyword is available in Windows IDL, the values
       used by this procedure are specific to the X windows device.

 PROCEDURE:
       If the user supplies a valid cursor shape value, it is set.  Otherwise,
       an interactive command loop is entered; it will continue until a valid
       value is given.
 MODIFICATION HISTORY:
       Converted to VAX 3100 workstations / IDL V2.  M. Greason, STX, May 1990.
       Avoid bad cursor parameter values  W. Landsman   February, 1991
       Don't change value of input param        W. Landsman   August 1995
       Use SIZE(/TNAME) instead of DATATYPE()   W. Landsman  October 2001

(See $IDLUTILS_DIR/goddard/pro/tv/curs.pro)

CURVAL

 NAME:
       CURVAL
 PURPOSE:   
       Cursor controlled display of image intensities and astronomical coords
 EXPLANATION
       CURVAL displays different information depending whether the user 
       supplied an image array, and/or a FITS header array

       Note that in the usual truecolor mode, the byte intensity returned by 
       CURVAL does not correspond to the byte scaled image value but rather 
       returns the maximum value in each color gun.
 CALLING SEQUENCE(S):
       curval          ;Display x,y and byte intensity (inten)
       
       curval, im   ;Display x,y,inten, and also pixel value (from image array)
       
       curval, hdr, [ im, OFFSET= , ZOOM=, FILENAME=, ALT=]        

 OPTIONAL INPUTS:
       Hdr  = FITS Header array
       Im  = Array containing values that are displayed.  Any type.

 OPTIONAL KEYWORD INPUTS:
      ALT - single character 'A' through 'Z' or ' ' specifying an alternate
            astrometry system present in the FITS header.    The default is
            to use the primary astrometry or ALT = ' '.   If /ALT is set,
            then this is equivalent to ALT = 'A'.   See Section 3.3 of
            Greisen & Calabretta (2002, A&A, 395, 1061) for information about
            alternate astrometry keywords.
      OFFSET - 2 element vector giving the location of the image pixel (0,0) 
               on the window display.   OFFSET can be positive (e.g if the 
               image is centered in a larger window) or negative (e.g. if the
               only the central region of an image much larger than the window
               is being displayed. 
               Default value is [0,0], or no offset.
       ZOOM - Scalar specifying the magnification of the window with respect
               to the image variable.    Use, for example, if image has been
               REBINed before display.
       FILENAME  = name of file to where CURVAL data can be saved.
               Data will only be saved if left or center mouse button
               are pressed.

 OUTPUTS:
       None.

 SIDE EFFECTS:
       X and Y values, etc., of the pixel under the cursor are constantly
       displayed.  
       Pressing left or center mouse button prints a line of output, and 
       starts a new line.
       Pressing right mouse button exits the procedure.
       If the keyword FILENAME is defined, the date and time, and a heading 
       will be printed in the file before the data.

 PROCEDURES CALLED:
       ADSTRING(), EXTAST, GSSSXYAD, RADEC, SXPAR(), UNZOOM_XY, XY2AD
 REVISION HISTORY:
       Written,  K. Rhode,  STX  May 1990
       Added keyword FILENAME  D. Alexander  June 1991
       Don't write to Journal file   W. Landsman    March 1993
       Use astrometry structure  W. Landsman      Feb 1994
       Modified for Mac IDL          I.   Freedman     April 1994
       Allow for zoomed or offset image  W. Landsman      Mar 1996
       Proper rounding of zoomed pixel values   W. Landsman/R. Hurt  Dec. 1997
       Remove unneeded calls to obsolete !ERR   W. Landsman   December 2000
       Replace remaining !ERR calls with !MOUSE.BUTTON W. Landsman Jan 2001
       Allow for non-celestial (e.g. Galactic) coordinates W. Landsman Apr 2003
       Work if RA/Dec reversed in CTYPE keyword  W. Landsman Feb. 2004
       Always call UNZOOM_XY for MOUSSE compatibility W. Landsman Sep. 2004
       Added ALT keyword  W. Landsman October 2004 
       Always test if offset/zoom supplied  W. Landsman  Feb 2008

(See $IDLUTILS_DIR/goddard/pro/tv/curval.pro)

DAOERF

 NAME:
	DAOERF
 PURPOSE:         
	Calulates the intensity, and derivatives, of a 2-d Gaussian PSF
 EXPLANATION:
	Corrects for the finite size of a pixel by integrating the Gaussian
	over the size of the pixel.    Used in the IDL-DAOPHOT sequence.   

 CALLING SEQUENCE:
	DAOERF, XIN, YIN, A, F, [ PDER ] 

 INPUTS:
	XIN - input scalar, vector or array, giving X coordinate values
	YIN - input scalar, vector or array, giving Y coordinate values, must 
		have same number of elements as XIN.
	A - 5 element parameter array describing the Gaussian
		A(0) - peak intensity
		A(1) - X position of peak intensity (centroid)
		A(2) - Y position of peak intensity (centroid)
		A(3) - X sigma of the gaussian (=FWHM/2.345)         
		A(4) - Y sigma of gaussian

 OUTPUTS:
	F - array containing value of the function at each (XIN,YIN) 
	    The number of output elements in F and PDER is identical with
		the number of elements in X and Y

 OPTIONAL OUTPUTS:
	PDER - 2 dimensional array of size (NPTS,5) giving the analytic
		derivative at each value of F with respect to each parameter A.

 REVISION HISTORY:
	Written: W. Landsman                October, 1987
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/idlphot/daoerf.pro)

DAO_VALUE

 NAME:
	DAO_VALUE
 PURPOSE:
	Returns the value of a DAOPHOT point-spread function at a set of points.
 EXPLANATION:
	The value of the point-spread function is the sum of a
	two-dimensional integral under a bivariate Gaussian function, and 
	a value obtained by interpolation in a look-up table.  DAO_VALUE will
	optionally compute the derivatives wrt X and Y

 CALLING SEQUENCE:
	Result = DAO_VALUE( xx, yy, gauss, psf, [ dvdx, dvdy ] )

 INPUTS:
	XX,YY   - the real coordinates of the desired point relative 
		to the centroid of the point-spread function.
	GAUSS  -  5 element vector describing the bivariate Gaussian
	GAUSS(0)- the peak height of the best-fitting Gaussian profile.
	GAUSS(1,2) - x and y offsets from the centroid of the point-spread 
		function to the center of the best-fitting Gaussian.
	GAUSS(3,4) - the x and y sigmas of the best-fitting Gaussian.
	PSF  -  a NPSF by NPSF array containing the look-up table.

 OUTPUTS:
    RESULT - the computed value of the point-spread function at
             a position XX, YY relative to its centroid (which 
             coincides with the center of the central pixel of the
             look-up table).

 OPTIONAL OUTPUTS:
       DVDX,DVDY - the first derivatives of the composite point-spread
             function with respect to x and y.

 NOTES
 	although the arguments XX,YY of the function DAO_VALUE
	are relative to the centroid of the PSF, the function RINTER which
	DAO_VALUE calls requires coordinates relative to the corner of the 
	array (see code).

 PROCEDURES CALLED:
	DAOERF, RINTER()
 REVISON HISTORY:
	Adapted to IDL by B. Pfarr, STX, 11/17/87 from 1986 STSDAS version
	of DAOPHOT
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/idlphot/dao_value.pro)

DATE

 NAME:
	DATE
 PURPOSE:
	Convert day-of-year to a DD-MMM-YYYY string

 CALLING SEQUENCE:
	D_String = DATE(Year, day )

 INPUTS:
	Year - Integer scalar specifying the year.   If the year contains only
		two digits, then it is assumed to indicate the number of 
		years after 1900. 

	Day - Integer scalar giving number of days after Jan 0 of the 
		specified year.    Can be larger than 366     

 OUTPUTS:
	D_String - String giving date in format '13-MAR-1986'

 RESTRICTIONS:
	Will not work for years before 100 AD 
 EXAMPLE:
	IDL> print, date(1997,279)
		'6-Oct-1997'

 MODIFICATION HISTORY:
       D.M. fecit  24 October,1983
	Work for years outside of the 19th century  W. Landsman  September 1997
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/date.pro)

DATE_CONV

 NAME:
     DATE_CONV
 PURPOSE:
     Procedure to perform conversion of dates to one of three possible formats.

 EXPLANATION:
     The following date formats are allowed

       format 1: real*8 scalar encoded as:
               year*1000 + day + hour/24. + min/24./60 + sec/24./60/60
               where day is the day of year (1 to 366)
       format 2: Vector encoded as:
               date[0] = year (eg. 2005)
               date[1] = day of year (1 to 366)
               date[2] = hour
               date[3] = minute
               date[4] = second
       format 3: string (ascii text) encoded as
               DD-MON-YEAR HH:MM:SS.SS
               (eg.  14-JUL-2005 15:25:44.23)
            OR
               YYYY-MM-DD HH:MM:SS.SS  (ISO standard)
               (eg.  1987-07-14 15:25:44.23 or 1987-07-14T15:25:44.23)
                   
       format 4: three element vector giving spacecraft time words
       from a Hubble Space Telescope (HST) telemetry packet.   Based on
       total number of secs since midnight, JAN. 1, 1979

       format 5: Julian day. As this is also a scalar, like format 1, 
       	the distinction between the two on input is made based on their
       	value. Numbers > 2300000 are interpreted as Julian days.

 CALLING SEQUENCE
       results = DATE_CONV( DATE, TYPE )

 INPUTS:
       DATE - input date in one of the possible formats. Must be scalar.
       TYPE - type of output format desired.  If not supplied then
               format 3 (real*8 scalar) is used.
                       valid values:
                       'REAL'  - format 1
                       'VECTOR' - format 2
                       'STRING' - format 3
                       'FITS' - YYYY-MM-DDTHH:MM:SS.SS'
                       'JULIAN' - Julian date
                       'MODIFIED' - Modified Julian date (JD-2400000.5)
               TYPE can be abbreviated to the single character strings 'R',
               'V', 'S', 'F', 'J', and 'M'.
               Nobody wants to convert TO spacecraft time (I hope!)
 OUTPUTS:
       The converted date is returned as the function value.

 EXAMPLES:
       IDL> print,date_conv('2006-03-13 19:58:00.00'),f='(f15.5)' 
             2006072.83194 
       IDL> print,date_conv( 2006072.8319444d,'F')
             2006-03-13T19:58:00.00
       IDL> print,date_conv( 2006072.8319444d,'V')
             2006.00      72.0000      19.0000      57.0000      59.9962
       IDL> print,date_conv( 2006072.8319444d,'J'), f='(f15.5)'
             2453808.33194


 HISTORY:
      version 1  D. Lindler  July, 1987
      adapted for IDL version 2  J. Isensee  May, 1990
      Made year 2000 compliant; allow ISO format input  jls/acc Oct 1998
      DJL/ACC Jan 1998, Modified to work with dates such as 6-JAN-1996 where
               day of month has only one digit.
      DJL, Nov. 2000, Added input/output format YYYY-MM-DDTHH:MM:SS.SS
      Replace spaces with '0' in output FITS format  W.Landsman April 2006
      Added Julian date capabilities on input and output.  M.Perrin, July 2007
      Removed spurious /WARN keyword to MESSAGE W.L. Feb 2012

(See $IDLUTILS_DIR/goddard/pro/astro/date_conv.pro)

DAYCNV

 NAME:
       DAYCNV
 PURPOSE:
       Converts Julian dates to Gregorian calendar dates

 CALLING SEQUENCE:
       DAYCNV, XJD, YR, MN, DAY, HR

 INPUTS:
       XJD = Julian date, positive double precision scalar or vector

 OUTPUTS:
       YR = Year (Integer)
       MN = Month (Integer)
       DAY = Day (Integer)
       HR = Hours and fractional hours (Real).   If XJD is a vector,
               then YR,MN,DAY and HR will be vectors of the same length.

 EXAMPLE:
       IDL> DAYCNV, 2440000.D, yr, mn, day, hr    

       yields yr = 1968, mn =5, day = 23, hr =12.   

 WARNING:
       Be sure that the Julian date is specified as double precision to
       maintain accuracy at the fractional hour level.

 METHOD:
       Uses the algorithm of Fliegel and Van Flandern (1968) as reported in
       the "Explanatory Supplement to the Astronomical Almanac" (1992), p. 604
       Works for all Gregorian calendar dates with XJD > 0, i.e., dates after
       -4713 November 23.
 REVISION HISTORY:
       Converted to IDL from Yeoman's Comet Ephemeris Generator, 
       B. Pfarr, STX, 6/16/88
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/daycnv.pro)

DBBUILD

 NAME:
	DBBUILD
 PURPOSE:
	Build a database by appending new values for every item.  
 EXPLANATION:
	The database must be opened for update (with DBOPEN) before calling 
	DBBUILD.     This version for IDL V6.1 or later.

 CALLING SEQUENCE:
	DBBUILD, [ v1, v2, v3, v4......v50, /NOINDEX, /SILENT, STATUS =  ]

 INPUTS:
	v1,v2....v50 - vectors containing values for all items in the database.
         V1 contains values for the first item, V2 for the second, etc.
         The number of vectors supplied must equal the number of items
         (excluding entry number) in the database.  The number of elements 
         in each vector should be the same.   A multiple valued item
         should be dimensioned NVALUE by NENTRY, where NVALUE is the number
         of values, and NENTRY is the number of entries.

 OPTIONAL INPUT KEYWORDS:
	/NOINDEX - If this keyword is supplied and non-zero then DBBUILD will
             *not* create an indexed file.    Useful to save time if
             DBBUILD is to be called several times and the indexed file need
             only be created on the last call

	/SILENT  - If the keyword SILENT is set and non-zero, then DBBUILD
	      will not print a message when the index files are generated

 OPTIONAL OUTPUT KEYWORD:
	STATUS - Returns a status code denoting whether the operation was
	      successful (1) or unsuccessful (0).  Useful when DBBUILD is
	      called from within other applications.

 EXAMPLE:
	Suppose a database named STARS contains the four items NAME,RA,DEC, and 
	FLUX.   Assume that one already has the four vectors containing the
	values, and that the database definition (.DBD) file already exists.

	IDL> !PRIV=2                  ;Writing to database requires !PRIV=2
	IDL> dbcreate,'stars',1,1   ;Create database (.DBF) & index (.DBX) file
	IDL> dbopen,'stars',1         ;Open database for update
	IDL> dbbuild,name,ra,dec,flux ;Write 4 vectors into the database

 NOTES:
	Do not call DBCREATE before DBBUILD if you want to append entries to
	an existing database

	DBBUILD checks that each value vector matches the idl type given in the
	database definition (..dbd) file, and that character strings are the 
	proper length. 
 PROCEDURE CALLS:
       DBCLOSE, DBINDEX, DBXPUT, DBWRT, IS_IEEE_BIG()
 REVISION HISTORY:
	Written          W. Landsman           March, 1989
	Added /NOINDEX keyword           W. Landsman        November, 1992
	User no longer need supply all items   W. Landsman  December, 1992 
	Added STATUS keyword, William Thompson, GSFC, 1 April 1994
	Added /SILENT keyword, William Thompson, GSFC, October 1995
	Allow up to 30 items, fix problem if first item was multiple value
				  W. Landsman    GSFC, July 1996
	Faster build of external databases on big endian machines 
				  W. Landsman    GSFC, November 1997  
       Use SIZE(/TNAME) for error mesage display  W.Landsman   July 2001
       Fix message display error introduced July 2001  W. Landsman   Oct. 2001 
       Make sure error message appears even if !QUIET is set W.L November 2006
       Major rewrite to use SCOPE_VARFETCH, accept 50 input items
                   W. Landsman    November 2006
      Fix warning if parameters have different # of elements W.L.  May 2010
      Fix warning if scalar parameter supplied W.L.  June 2010
      Fix for when first parameter is multi-dimensioned W.L. July 2010
      Check data type of first parameter W.L. Jan 2012

(See $IDLUTILS_DIR/goddard/pro/database/dbbuild.pro)

DBCIRCLE

 NAME:
      DBCIRCLE
 PURPOSE:
      Find sources in a database within specified radius of specified center
 EXPLANATION:
      Database must include items named 'RA' (in hours) and 'DEC' (in degrees)
      and must have previously been opened with DBOPEN

 CALLING SEQUENCE:
     list = DBCIRCLE( ra_cen, dec_cen, [radius, dis, sublist, /SILENT, 
                                /GALACTIC, TO_B1950, /TO_J2000, COUNT= ] )   

 INPUTS:
       RA_CEN - Right ascension of the search center in decimal HOURS, scalar
       DEC_CEN - Declination of the search center in decimal DEGREES, scalar
               RA_CEN and DEC_CEN should be in the same equinox as the 
               currently opened catalog.

 OPTIONAL INPUT:
       RADIUS - Radius of the search field in arc minutes, scalar.
               DBCIRCLE prompts for RADIUS if not supplied.
       SUBLIST - Vector giving entry numbers in currently opened database
               to be searched.  Default is to search all entries

 OUTPUTS:
     LIST - Vector giving entry numbers in the currently opened catalog
            which have positions within the specified search circle
            LIST is set to -1 if no sources fall within the search circle

 OPTIONAL OUTPUT
       DIS -  The distance in arcminutes of each entry specified by LIST
               to the search center (given by RA_CEN and DEC_CEN)

 OPTIONAL KEYWORD INPUT:
       /GALACTIC - if set, then the first two parameters are interpreted as
                 Galactic coordinates in degrees, and is converted internally
                 to J2000 celestial to search the database.   
       /SILENT - If this keyword is set, then DBCIRCLE will not print the 
               number of entries found at the terminal
       /TO_J2000 - If this keyword is set, then the entered coordinates are
               assumed to be in equinox B1950, and will be converted to
               J2000 before searching the database
       /TO_B1950 - If this keyword is set, then the entered coordinates are
               assumed to be in equinox J2000, and will be converted to
               B1950 before searching the database
               NOTE: The user must determine on his own whether the database
               is in B1950 or J2000 coordinates.
 OPTIONAL KEYWORD OUTPUT:
       COUNT - - Integer scalar giving the number of valid matches
 METHOD:
       A DBFIND search is first performed on a square area of given radius.
       The list is the restricted to a circular area by using GCIRC to 
       compute the distance of each object to the field center.

 RESTRICTIONS;
       The database must have items 'RA' (in hours) and 'DEC' (in degrees).
       Alternatively, the database could have items RA_OBJ and DEC_OBJ 
      (both in degrees)
 EXAMPLE:
       Find all Hipparcos stars within 40' of the nucleus of M33
       (at J2000 1h 33m 50.9s 30d 39' 36.7'')

       IDL> dbopen,'hipparcos'
       IDL> list = dbcircle( ten(1,33,50.9), ten(3,39,36.7), 40)

 PROCEDURE CALLS:
       BPRECESS, DBFIND(), DBEXT, DB_INFO(), GCIRC, GLACTC, JPRECESS
 REVISION HISTORY:
      Written W. Landsman     STX           January 1990
      Fixed search when crossing 0h         July 1990
      Spiffed up code a bit     October, 1991
      Leave DIS vector unchanged if no entries found W. Landsman July 1999
      Use maximum declination, rather than declination at field center to
      correct RA for latitude effect    W. Landsman   September 1999
      Added COUNT, GALACTIC keywords  W. Landsman   December 2008
      Fix problem when RA range exceeds 24h  W. Landsman   April 2009
      Work as advertised for RA_OBJ field  W. Landsman June 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbcircle.pro)

DBCLOSE

 NAME:
       DBCLOSE
 PURPOSE:
       procedure to close a data base file

 CALLING SEQUENCE:  
       dbclose

 INPUTS:
       None

 OUTPUTS
       None

 SIDE EFFECTS:
       the data base files currently opened are closed

 PROCEDURE CALLS:
       DB_INFO(), HOST_TO_IEEE
 HISTORY:
       version 2  D. Lindler  Oct. 1987
       For IDL version 2      August 1990
       William Thompson, GSFC/CDS (ARC), 30 May 1994
                Added support for external (IEEE) data format
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/database/dbclose.pro)

DBCOMPARE

NAME:
DBCOMPARE
PURPOSE:
Display two entries in an IDL database side by side in a column format

CALLING SEQUENCE:
dbcompare, list1, list2, [items, TEXTOUT= , /DIFF]

INPUTS:
list1 - Integer scalar giving first entry number to be compared.
list2 - Integer scalar giving second entry number to be compared.

OPTIONAL INPUT-OUTPUT:
items - items to be compared, if not supplied then all items will be
compared. The items can be specified in any of the following ways:

form 1 scalar string giving item(s) as list of names
separated by commas
form 2 string array giving list of item names
form 3 string of form '$filename' giving name
of text file containing items (one item per line) line)
form 4 integer scalar giving single item number or
integer vector list of item numbers
form 5 Null string specifying interactive selection. This
is the default if 'items' is not supplied
form 6 '*' select all items (= default)

If items was undefined or a null string on input, then
on output it will contain the items interactively selected.

OPTIONAL INPUT KEYWORDS:
/DIFF - If this keyword is set and non-zero, then only the items
in the database that differ will be printed

TEXTOUT - Scalar Integer (1-7) Used to determine output device. See
TEXTOPEN for more info.

SYSTEM VARIABLES:
Output device controlled by non-standard system variable !TEXTOUT, if
TEXTOUT keyword is not used.

EXAMPLE:
Display entries 3624 and 3625 in column form showing only the items
that differ.
IDL> dbcompare,3624,3625,/diff

PROCEDURES USED:
DB_INFO(), DB_ITEM, DB_ITEM_INFO(), DBRD, DBXVAL()
TEXTOPEN, TEXTCLOSE
HISTORY:
Written, W. Landsman July 1996
Fix documentation, add Syntax display W. Landsman November 1998
Replace DATATYPE() with size(/TNAME) W. Landsman November 2001
Assume since V5.5, remove VMS call W. Landsman September 2006
Fix problem with multiple values when /DIFF set W. Landsman April 2007

(See $IDLUTILS_DIR/goddard/pro/database/dbcompare.pro)

DBCREATE

 NAME: 
       DBCREATE
 PURPOSE:      
       Create a new data base (.dbf), index (.dbx) or description (.dbh) file
 EXPLANATION:
       A database definition (.dbd) file must already exist in the current
       directory or in a ZDBASE directory.    The new .dbf, .dbx and/or .dbh
       files will be written to the same directory.   So if the .dbd file is 
       in a ZDBASE directory, then the user must have write privilege to that 
       directory

       This version allows record length to be larger than 32767 bytes
 CALLING SEQUENCE:     
       dbcreate, name,[ newindex, newdb, maxitems]  [,/EXTERNAL, MAXENTRY=]  

 INPUTS:       
       name- name of the data base (with no qualifier), scalar string. 
               The description will be read from the file "NAME".dbd 
               Maximum length of name is 19 characters.

 OPTIONAL INPUTS:      
       newindex - if non-zero then a new index file is created,
               otherwise it is assumed that changes do not affect the
               index file. (default=0)
       newdb - if non-zero then a new data base file (.dbf) will
               be created. Otherwise changes are assumed not to affect
               the file's present format.
       maxitems - maximum number of items in data base.
               If not supplied then the number of items is
               limited to 200.

 OUTPUTS:
       NONE.

 OPTIONAL INPUT KEYWORDS:       

       external - If set, then the database is written with an external data
               representation.  This allows the database files to be used on
               any computer platform, e.g. through NFS mounts, but some
               overhead is added to reading the files.  The default is to
               write the data in the native format of the computer being used.

               This keyword is only paid attention to if NEWDB or NEWINDEX
               are nonzero.  Otherwise, the database is opened to find
               out if it uses external representation or not.

               Extreme caution should be used if this keyword is used with
               only NEWINDEX set to a nonzero value.  This mode is allowed so
               that databases written on machines which already use the
               external data representation format, e.g. Sun workstations, to
               be marked external so that other machines can read them.


       MAXENTRY - positive integer giving the maximum number of entries in the
               database (needed to adjust the size of the index file).   This
               keyword can be used to supercede the  #maxentries line in the 
               .dbd file (the larger of the two numbers will be used).
 PROCEDURE CALLS:      
       GETTOK(), FIND_WITH_DEF(), ZPARCHECK

 RESTRICTIONS: 
       If newdb=0 is not specified, the changes to the .dbd file can
       not alter the length of the records in the data base file.
       and may not alter positions of current fields in the file.
       permissible changes are:
               1) utilization of spares to create a item or field
               2) change in field name(s)
               3) respecification of index items
               4) changes in default print formats
               5) change in data base title
               6) changes in pointer specification to other data
                       data bases

       !priv must be 2 or greater to execute this routine.


 SIDE EFFECTS:  
       data base description file ZDBASE:name.dbh is created
       and optionally ZDBASE:name.dbf (data file) and
       ZDBASE.dbx (index file) if it is a new data base.

 REVISION HISTORY:     
       D. Lindler, GSFC/HRS, October 1987
       Modified:  Version 1, William Thompson, GSFC, 29 March 1994
                  Version 2, William Thompson, GSFC/CDS (ARC), 28 May 1994
                  Added EXTERNAL keyword.
       Version 4, William Thompson, GSFC, 3 November 1994
                       Modified to allow ZDBASE to be a path string.
       8/14/95  JKF/ACC - allow EXTERNAL data for newindex OR newdb modes.
       Make sure all databases closed before starting W. Landsman June 1997
       Added new unsigned and 64 bit integer datatypes W. Landsman July 2001
       Make sure to use lowercase filenames on Unix W. Landsman May 2006
       Added MAXENTRY keyword   W. Landsman July 2006
       Assume since V5.5, remove obsolete keywords to OPEN W. Landsman Sep2006
       No longer required to be a ZDBASE directory  W. Landsman Feb 2008
       Fix Feb 2008 bug when files are in current dir W. L.  May 2008
       Fix May 2008 bug when files are not in current dir (sigh) W. L. May 2008
       Warn if database length exceeds 32767 bytes  W.L. Dec 2009
       Remove spurious warning that database name is too long W.L. April 2010
       Support entry lengths larger than 32767 bytes W.L. Oct. 2010
       Better testing for valid print formats W.L. Nov 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbcreate.pro)

DBDELETE

 NAME:
       DBDELETE
 PURPOSE:
       Deletes specified entries from data base

 CALLING SEQUENCE:
       DBDELETE, list, [ name, /DEBUG ]   

 INPUTS:
       list - list of entries to be deleted, scalar or vector
       name - optional name of data base, scalar string.  If not specified
               then the data base file must be previously opened for update 
               by DBOPEN.

 OPERATIONAL NOTES:
       !PRIV must be at least 3 to execute.

 SIDE EFFECTS:
       The data base file (ZDBASE:name.dbf) is modified by removing the
       specified entries and reordering the remaining entry numbers
       accordingly (ie. if you delete entry 100, it will be replaced
       by entry 101 and the database will contain 1 less entry.

 EXAMPLE:
        Delete entries in a database STARS where RA=DEC = 0.0

        IDL> !PRIV= 3                           ;Set privileges
        IDL> dbopen,'STARS',1                   ;Open for update
        IDL> list = dbfind('ra=0.0,dec=0.0')    ;Obtain LIST vector
        IDL> dbdelete, list             ;Delete specified entries from db

 NOTES:
       The procedure is rather slow because the entire database is re-
       created with the specified entries deleted.
 OPTIONAL KEYWORD INPUT:
        DEBUG - if this keyword is set and non-zero, then additional 
               diagnostics will be printed as each entry is deleted.
 COMMON BLOCKS:
       DBCOM
 PROCEDURE CALLS:
       DBINDEX, DB_INFO(), DBOPEN, DBPUT, ZPARCHECK
 HISTORY
       Version 2  D. Lindler  July, 1989
       Updated documentation   W. Landsman    December 1992
       William Thompson, GSFC, 28 February 1995
                       Fixed bug when external representation used.
       Fixed for case where second parameter supplied W. Landsman April 1996
       Use keyword DEBUG rather than !DEBUG   W. Landsman    May 1997
       Don't call DBINDEX if no indexed items  W. Landsman May 2006  
       Use TRUNCATE_LUN if V5.6 or later W. Landsman   Sep 2006 
       Fix problem when deleting last entry   W. Landsman Mar 2007
       Assume since V5.6 so TRUNCATE_LUN is available   W. Landsman

(See $IDLUTILS_DIR/goddard/pro/database/dbdelete.pro)

DBEDIT

 NAME:
      DBEDIT

 PURPOSE:
       Interactively edit specified fields in an IDL database. 
 EXPLANATION:
       The value of each field is displayed, and the user has the option
       of changing or keeping the value.  Widgets will be used if they
       are available.

 CALLING SEQUENCE:
       dbedit, list, [ items ]

 INPUTS:
       list - scalar or vector of database entry numbers.  Set list = 0 to 
       interactively add a new entry to a database.  Set list = -1 to edit 
       all entries.

 OPTIONAL INPUTS:
       items - list of items to be edited.  If omitted, all fields can be 
               edited.      

 KEYWORDS:
       BYTENUM = If set, treat byte variables as numbers instead of
                 characters.

 COMMON BLOCKS:
       DB_COM -- contains information about the opened database.
       DBW_C -- contains information intrinsic to this program.

 SIDE EFFECTS:
       Will update the database files.

 RESTRICTIIONS:
       Database must be opened for update prior to running
       this program.  User must be running DBEDIT from an 
       account that has write privileges to the databases.  

       If one is editing an indexed item, then after all edits are complete,
       DBINDEX will be called to reindex the entire item.    This may
       be time consuming.

       Cannot be used to edit items with multiple values

 EXAMPLE:
       Suppose one had new parallaxes for all stars fainter than 5th magnitude
       in the Yale Bright Star Catalog and wanted to update the PRLAX and
       PRLAX_CODE fields with these new numbers

       IDL> !priv=2                    
       IDL> dbopen, 'yale_bs', 1            ;Open catalog for update
       IDL> list = dbfind( 'v>5')     ;Find fainter than 5th magnitude
       IDL> dbedit, list, 'prlax, prlax_code'   ;Manual entry of new values

 PROCEDURE:
       (1) Use the cursor and point to the value you want to edit.   
       (2) Type the new field value over the old field value.
       (3) When you are done changing all of the field values for each entry
       save the entry to the databases by pressing 'SAVE ENTRY TO DATABASES'.
       Here all of the values will be checked to see if they are the correct
       data type.  If a field value is not of the correct data type, it will
       not be saved.  

       Use the buttons "PREV ENTRY" and "NEXT ENTRY" to move between entry 
       numbers.  You must save each entry before going on to another entry in 
       order for your changes to be saved.

       Pressing "RESET THIS ENTRY" will remove any unsaved changes to the 
       current entry.

REVISION HISTORY:
       Adapted from Landsman's DBEDIT
       added widgets,  Melissa Marsh, HSTX, August 1993
       do not need to press return after entering each entry,
                       fixed layout problem on SUN,
                       Melissa Marsh, HSTX, January 1994
       Only updates the fields which are changed. Joel Offenberg, HSTX, Mar 94
       Corrected test for changed fields  Wayne Landsman  HSTX, Mar 94
       Removed a couple of redundant statements W. Landsman HSTX Jan 96
       Converted to IDL V5.0   W. Landsman   September 1997
       Replace DATAYPE() with size(/TNAME)   W. Landsman   November 2001
       Work for entry numbers > 32767     W. Landsman   December 2001
       Added /BYTENUM  William Thompson        13-Mar-2006
       Use DIALOG_MESSAGE for error messages  W. Landsman  April 2006
       Assume since V5.5, remove VMS support  W. Landsman  Sep 2006

(See $IDLUTILS_DIR/goddard/pro/database/dbedit.pro)

DBEDIT_BASIC

 NAME:
       DBEDIT_BASIC
 PURPOSE:
       Subroutine of DBEDIT_BASIC to edit a database on a dumb terminal.
 EXPLANATION:
       Interactively edit specified fields in a database.  The
       value of each field is displayed, and the user has the option
       of changing or keeping the value.

 CALLING SEQUENCE:
       dbedit_basic, list, [ items ]

 INPUTS:
       list - scalar or vector of database entry numbers.  Set LIST=0
               to interactively add a new entry to a database.

 OPTIONAL INPUTS
       items - list of items to be edited.  If not supplied, then the
               value of every field will be displayed.

 NOTES:
       (1) Database must be opened for update (dbopen,<dbname>,1) before
       calling DBEDIT_BASIC.  User must have write privileges on the database
       files.
       (2) User gets a second chance to look at edited values, before
       they are actually written to the database

 PROMPTS:
       The item values for each entry to be edited are first displayed
       User is the asked "EDIT VALUES IN THIS ENTRY (Y(es), N(o), or Q(uit))?
       If user answers 'Y' or hits RETURN, then each item is displayed
       with its current value, which the user can update.  If user answered
       'N' then DBEDIT_BASIC skips to the next  entry.   If user answers 'Q'
       then DBEDIT will exit, saving all previous changes.

 EXAMPLE:
       Suppose V magnitudes (V_MAG) in a database STARS with unknown values 
       were assigned a value of 99.9.  Once the true values become known, the
       database can be edited

       IDL> !PRIV=2 & dbopen,'STARS',1         ;Open database for update
       IDL> list =  dbfind('V_MAG=99.9')       ;Get list of bad V_MAG values
       IDL> dbedit,list,'V_MAG'       ;Interactively insert good V_MAG values

 REVISION HISTORY:
       Written  W. Landsman     STX        April, 1989
       Rename DBEDIT_BASIC from DBEDIT            July, 1993
       Converted to IDL V5.0   W. Landsman   September 1997
       Change DATATYPE() to size(/TNAME)  W. Landsman   November 2001

(See $IDLUTILS_DIR/goddard/pro/database/dbedit_basic.pro)

DBEXT

 NAME:
       DBEXT
 PURPOSE:
       Extract values of up to 12 items from an IDL database 
 EXPLANATION:
       Procedure to extract values of up to 12 items from
       data base file, and place into IDL variables

 CALLING SEQUENCE:
       dbext,list,items,v1,[v2,v3,v4,v5,v6,v7,v8,v9,v10,v11,v12]

 INPUTS:
       list - list of entry numbers to be printed, vector or scalar
               If list = -1, then all entries will be extracted.
               list may be converted to a vector by DBEXT 
       items - standard item list specification.  See DBPRINT for 
               the 6 different ways that items may be specified. 

 OUTPUTS:
       v1...v12 - the vectors of values for up to 12 items.

 EXAMPLE:
       Extract all RA and DEC values from the currently opened database, and
       place into the IDL vectors, IDLRA and IDLDEC.

               IDL> DBEXT,-1,'RA,DEC',idlra,idldec

 HISTORY
       version 2  D. Lindler  NOV. 1987
       check for INDEXED items   W. Landsman   Feb. 1989
       Converted to IDL V5.0   W. Landsman   September 1997
       Avoid EXECUTE() call for V6.1 or later  W. Landsman   December 2006
       Assume since V6.1   W. Landsman June 2009

(See $IDLUTILS_DIR/goddard/pro/database/dbext.pro)

DBEXT_DBF

 NAME:
       DBEXT_DBF
 PURPOSE:
       Subroutine of DBEXT to extract values of up to 18 items from a database 
 EXPLANATION:
       This is a subroutine of DBEXT, which is the routine a user should 
       normally use.

 CALLING SEQUENCE:
       dbext_dbf,list,dbno,sbyte,nbytes,idltype,nval,v1,[ v2,v3,v4,v5,v6,v7,
                  v8,v9,v10,v11,v12,v13,v14,v15,v16,v17,v18 ITEM_DBNO = ]

 INPUTS:
       list - list of entry numbers to extract desired items.   It is the 
               entry numbers in the primary data base unless dbno is greater 
               than or equal to -1.  In that case it is the entry number in 
               the specified data base.
       dbno - number of the opened db file
               if set to -1 then all data bases are included
       sbyte - starting byte in the entry.  If single data base then it must 
               be the starting byte for that data base only and not the 
               concatenation of db records 
       nbytes - number of bytes in the entry
       idltype - idl data type of each item to be extracted
       nval - number of values per entry of each item to be extracted

 OUTPUTS:
       v1...v18 - the vectors of values for up to 18 items

 OPTIONAL INPUT KEYWORD:
       item_dbno - A vector of the individual database numbers for each item.
               Simplifies the code for linked databases
 PROCEDURE CALLS:
       DB_INFO(), DB_ITEM_INFO(), DBRD, DBXVAL(), IS_IEEE_BIG(), IEEE_TO_HOST
 HISTORY
       version 1  D. Lindler  Nov. 1987
       Extract multiple valued entries    W. Landsman   May 1989
       William Thompson, GSFC/CDS (ARC), 1 June 1994
               Added support for external (IEEE) representation.
       Work with multiple element string items  W. Landsman  August 1995
       Increase speed for external databases on IEEE machines WBL August 1996
       IEEE conversion implemented on blocks of entries using BIG
       Added keyword ITEM_DBNO     R. Schwartz, GSFC/SDAC, August 1996
       Return a vector even if only 1 value W. Thompson  October 1996
       Change variable name of BYTESWAP to BSWAP  W. Thompson Mar 1997
       Use /OVERWRITE with reform   W. Landsman   May 1997
       Increase maximum number of items to 18  W. Landsman  November 1999
       2 May 2003, W. Thompson, Use DBXVAL with BSWAP instead of IEEE_TO_HOST.
       Avoid EXECUTE() for V6.1 or later  W. Landsman Jan 2007 
       Assume since V6.1  W. Landsman June 2009
       Change arrays to LONG to support entries >32767 bytes WL Oct 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbext_dbf.pro)

DBEXT_IND

 NAME:
       DBEXT_IND
 PURPOSE:
       routine to read a indexed item values from index file

 CALLING SEQUENCE:  
       dbext_ind,list,item,dbno,values

 INPUTS:
       list - list of entry numbers to extract values for
               (if it is a scalar, values for all entries are extracted)
       item - item to extract
       dbno - number of the opened data base

 OUTPUT:
       values - vector of values returned as function value
 HISTORY:
       version 1  D. Lindler  Feb 88
       Faster processing of string values    W. Landsman   April, 1992
       William Thompson, GSFC/CDS (ARC), 30 May 1994
               Added support for external (IEEE) data format
       Allow multiple valued (nonstring) index items W. Landsman  November 2000      
       Use 64bit integer index for large databases W. Landsman  February 2001
       Fix sublisting of multiple valued index items W. Landsman  March 2001
       Check whether any supplied entries are valid W. Landsman Jan 2009

(See $IDLUTILS_DIR/goddard/pro/database/dbext_ind.pro)

DBFIND()

 NAME: 
    DBFIND()
 PURPOSE:      
     Search data base for entries with specified characteristics
 EXPLANATION:  
     Function to search data base for entries with specified
     search characteristics.

 CALLING SEQUENCE:     
     result = dbfind(spar,[ listin, /SILENT, /FULLSTRING, ERRMSG=, Count = ])

 INPUTS:       
     spar - search_parameters (string)...each search parameter 
               is of the form:

               option 1) min_val < item_name < max_val
               option 2) item_name = value
               option 3) item_name = [value_1, value_10]
                       Note: option 3 is also the slowest.
               option 4) item_name > value
               option 5) item_name < value
               option 6) item_name = value(tolerance) ;eg. temp=25.0(5.2)
               option 7) item_name                     ;must be non-zero

               Multiple search parameters are separated by a comma.
               eg.     'cam_no=2,14<ra<20'

               Note: < is interpreted as less than or equal.
                     > is interpreted as greater than or equal.
       
               RA and DEC keyfields are stored as floating point numbers 
               in the data base may be entered as HH:MM:SEC and
               DEG:MIN:SEC. Where:

                       HH:MM:SEC   equals  HH + MM/60.0  + SEC/3600.
                       DEG:MIN:SEC equals DEG + MIN/60.0 + SEC/3600.
                       
               For example:
                       40:34:10.5 < dec < 43:25:19 , 8:22:1.0 < ra < 8:23:23.0

               Specially encoded date/time in the data base may
               be entered by  CCYY/DAY:hr:min:sec which is
               interpreted as  
                       CCYY*1000+DAY+hr/24.0+min/24.0/60.+sec/24.0/3600.
               If a two digit year is supplied and YY GE 40 then it is 
               understood to refer to year 1900 +YY;  if YY LT 40 then it is 
               understood to refer to year 2000 +YY

               For example
                       1985/201:10:35:30<date_time<1985/302:10:33:33.4
               would specify all entries between:
                       year 1985 day 201 at 10:35:30 to
                       day 302 at 10:33:33.4
               The date/time may also be encoded as:
                       DD-MMM-YEAR HH::MM:SS.SS        
                       eg.  12-JUL-86 10:23:33.45
               (this is the format of system variable !stime)

               Multiple search parameters may be stored in a string
               array (one parameter per array element) instead of
               concatenating them with commas in a single string.
               Example:
                       input_array = strarr(2)
                       input_array[0] = '14<ra<16'   ; 14-16 hrs of ra.
                       input_array[1] = '8<dec<20'   ; + 8-20 deg. decl.

 OPTIONAL INPUT:       
       listin - gives list of entries to be searched.  If not supplied or 
               set to -1 then all entries are searched.

 OUTPUT:       
       List of ENTRY numbers satisfying search characteristics
               is returned as the function value.

 OPTIONAL INPUT KEYWORDS:      
       /SILENT  - If the keyword SILENT is set and non-zero, then DBFIND
               will not print the number of entries found.

       /FULLSTRING - By default, one has a match if a search string is 
               included in any part of a database value (substring match).   
               But if /FULLSTRING is set, then all characters in the database
               value must match the search string (excluding leading and 
               trailing blanks).    Both types of string searches are case
               insensitive.

       ERRMSG   = If defined and passed, then any error messages will
                  be returned to the user in this parameter rather
                  than depending on the MESSAGE routine in IDL.  If no
                  errors are encountered, then a null string is
                  returned.  In order to use this feature, ERRMSG must
                  be defined first, e.g.

                       ERRMSG = ''
                       DB_ITEM, ERRMSG=ERRMSG, ...
                       IF ERRMSG NE '' THEN ...;

 OPTIONAL OUTPUT KEYWORD:
       COUNT - Integer scalar giving the number of valid matches
 PROCEDURE CALLS:
       DB_INFO, DB_ITEM, DB_ITEM_INFO, DBEXT, DBEXT_IND, DBFIND_ENTRY,
       DBFIND_SORT, DBFPARSE, DBRD, DBSEARCH, ZPARCHECK,IS_IEEE_BIG

 RESTRICTIONS: 
       The data base must be previously opened with DBOPEN.

 SIDE EFFECTS: 
       The obsolete system variable !ERR is set to number of entries found

 REVISION HISTORY:
       Written     :   D. Lindler, GSFC/HRS, November 1987
       Version 2, Wayne Landsman, GSFC/UIT (STX), 1 April 1994
                       Added FULLSTRING keyword.
       Version 3, William Thompson, GSFC, 1 April 1994
                       Added check for empty database
       Version 4, William Thompson, GSFC, 5 April 1994
                       Changed so that !ERR is zero when database is empty,
                       and LISTIN is returned, based on discussion with Wayne
                       Landsman.
       Version 5, Wayne Landsman, GSFC/UIT (STX), 26 May 1994
                       Added error message when database is empty.
       Version 6, William Thompson, GSFC, 14 March 1995
                       Added FULLSTRING keyword to DBFIND_SORT call
       Version 7, Richard Schwartz, GSFC/SDAC 23 August 1996
                       Move external to host conversion from DBRD to
                       operation on extracted values only.
       Version 8, William Thompson, GSFC, 3 December 1996
                       Renamed BYTESWAP variable to BSWAP--appeared to be
                       conflicting with function of same name.
       Version 9, William Thompson, GSFC, 17-Mar-1997
                       Added keyword ERRMSG
       Version 10, July, 1997  W. Landsman, added CATCH errors
       Converted to IDL V5.0   W. Landsman   October 1997
       Update documentation for new Y2K compliant DBFPARSE W. Landsman Nov 1998
       Suppress empty database message with /SILENT, W. Landsman Jan 1999
       Added COUNT keyword, deprecate !ERR        W. Landsman March 2000
       Added new unsigned & 64bit datatypes       W. Landsman July 2001
       Fix possible floating illegand operand error W. Landsman July 2009
       Change arrays to LONG to support entries >32767 bytes W.L. Oct. 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbfind.pro)

DBFIND_ENTRY

 NAME:
       DBFIND_ENTRY
 PURPOSE:
       Subroutine of DBFIND to perform an entry number search 
 EXPLANATION:
       This is a subroutine of dbfind and is not a standalone procedure
       It performs a entry number search.

 CALLING SEQUENCE:
       dbfind_entry, type, svals, nentries, values, [COUNT = ]

 INPUTS: 
       type - type of search (output from dbfparse)
       svals - search values (output from dbfparse)
       values - array of values to search
 OUTPUT:
       good - indices of good values
 OPTIONAL OUTPUT KEYWORD:
       Count - integer scalar giving the number of valid matches
 SIDE EFFECTS"
       The obsolete system variable !err is set to number of good values

 REVISION HISTORY:
       D. Lindler  July,1987
       Fixed test for final entry number  W. Landsman    Sept. 95       
       Converted to IDL V5.0   W. Landsman   September 1997
       Added COUNT keyword, deprecate !ERR  W. Landsman   March 2000
       Better checking of out of range values  W. Landsman February 2002

(See $IDLUTILS_DIR/goddard/pro/database/dbfind_entry.pro)

DBFIND_SORT

 NAME:
       DBFIND_SORT   
 PURPOSE:
       Subroutine of DBFIND to perform a search using sorted values 
 EXPLANATION:
       This is a subroutine of dbfind and is not a standalone procedure
       It is used to limit the search using sorted values  

 CALLING SEQUENCE:
       dbfind_sort, it, type, svals, list, [/FULLSTRING, COUNT = ]

 INPUT: 
       it - item number, scalar
       type - type of search (output from dbfparse)
       svals - search values (output from dbfparse)

 INPUT/OUTPUT:
       list - found entries

 OPTIONAL INPUT KEYWORD:
       /FULLSTRING - By default, one has a match if a search string is 
               included in any part of a database value (substring match).   
               But if /FULLSTRING is set, then all characters in the database
               value must match the search string (excluding leading and 
               trailing blanks).    Both types of string searches are case
               insensitive.
 OPTIONAL OUTPUT KEYWORD
       Count - Integer scalar giving the number of matches found
 SYSTEM VARIABLES:
       The obsolete system variable !err is set to number of good values
       !ERR = -2 for an invalid search
 PROCEDURES CALLED:
       DB_INFO(), DB_ITEM_INFO(), DBSEARCH() 
 REVISION HISTORY:
       D. Lindler  July,1987
       William Thompson, GSFC/CDS (ARC), 30 May 1994
               Added support for external (IEEE) data format
       William Thompson, GSFC, 14 March 1995 Added keyword FULLSTRING
       Minimize use of obsolete !ERR variable   W. Landsman  February 2000
       Added COUNT keyword, deprecate !ERR W. Landsman  March 2000
       Use 64 bit integers V5.2 or later
       Include new IDL unsigned & 64 bit integer datatypes W.Landsman July 2001
       Make sure returned list vector is LONG  W. Landsman August 2001
       Work on string items   W. Landsman November 2009
       Don't use VALUE_LOCATE on a single value  W. Landsman November 2009
       Use VALUE_LOCATE even for equal values W. Landsman December 2009
       Fix bug allowing negative FIRST values, William Thompson, 10 May 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbfind_sort.pro)

DBFPARSE

 NAME:
     DBFPARSE
 PURPOSE:
     Parse the search string supplied to DBFIND.   Not a standalone routine

 CALLING SEQUENCE:
     DBFPARSE, [ spar, items, stype, values ]

 INPUTS:
     spar - search parameter specification, scalar string

 OUTPUTS:
     items - list of items to search on
     stype - search type, numeric scalar
               0    item=values(j,0)
               -1   item>values(j,0)
               -2   item<values(j,1)
               -3   values(j,0)<item<values(j,1)
               -4   item is non zero
               -5   item=values(j,0) within tolerance values(j,1)
               0<   items in list values(j,i) for i=0,stype-1
     values - search values, 20 x 10 string array, can parse a string
               with up to 20 items specifications, each item can have 10
               values

 REVISION HISTORY:  
     D. Lindler NOV, 1987
     Check for valid numeric values before assuming a date string
     W. Landsman                    July, 1993
     Accept four digit years when in ccyy/doy format W. Landsman   October 1998
     Don't do DATE/Time test for string items  W. Landsman   July 2006

(See $IDLUTILS_DIR/goddard/pro/database/dbfparse.pro)

DBGET

 NAME:
       DBGET
 PURPOSE:
       Find entry numbers which contain specified values of a given item.
 EXPLANATION:
       DBGET() is useful as an alternative to DBFIND() when the desired 
       search values are not easily expressed as a string.  

 CALLING SEQUENCE:
       list = dbget( item, values, [ listin ], /SILENT, /FULLSTRING )

 INPUTS:
       item - Item name or number
       values -  scalar or vector containing item values to search for.

 OPTIONAL INPUTS:
       listin - list of entries to be searched.  If not supplied, or
               set to -1, then all entries are searched

 OUTPUT:
       list - vector giving the entry number of entries containing desired
               item values.  The number of elements in  LIST may be different 
               from that of VALUE, since a value might be located zero, once, 
               or many times in the database.  Use the function DBMATCH if a 
               one to one correspondence is desired between VALUES and LIST. 
 OPTIONAL INPUT KEYWORDS:
       /SILENT - If this keyword is set, then DBGET will not display
               the number of entries found
       /FULLSTRING - By default, one has a match if a search string is 
               included in any part of a database value (substring match).   
               But if /FULLSTRING is set, then all characters in the database
               value must match the search string (excluding leading and 
               trailing blanks).    Both types of string searches are case
               insensitive.
 OPTIONAL OUTPUT KEYWORD:
       COUNT - Integer scalar giving the number of valid matches

 RESTRICTIONS:
       When linked databases are opened together, DBGET can only be used to
       search on items in the primary database.
 EXAMPLE:
       Get info on selected HD stars in Bright Star catalogue

       IDL> dbopen, 'YALE_BS' 
       IDL> hdno = [1141,2363,3574,4128,6192,6314,6668]    ;Desired HD numbers
       IDL> list = dbget( 'HD', hdno )        ;Get corresponding entry numbers

 SYSTEM VARIABLES:
       The obsolete system variable !ERR is set to number of entries found
 REVISION HISTORY:
       Written,    W. Landsman      STX     February, 1989
       William Thompson, GSFC, 14 March 1995 Added keyword FULLSTRING
       Converted to IDL V5.0   W. Landsman   September 1997
       Added COUNT keyword, deprecate !ERR        W. Landsman March 2000
       Fix bug introduced March 2000              W. Landsman November 2000
       Fix possible bug when sublist supplied    W. Landsman August 2008

(See $IDLUTILS_DIR/goddard/pro/database/dbget.pro)

DBHELP

 NAME:
     DBHELP
 PURPOSE:
     List available databases or items in the currently open database
 EXPLANATION:
     Procedure to either list available databases (if no database is 
     currently open) or the items in the currently open database.

 CALLING SEQUENCE:  
     dbhelp, [ flag , TEXTOUT=, /SORT ]

 INPUT:
     flag - (optional) if set to nonzero then item or database
             descriptions are also printed
             default=0
             If flag is a string, then it is interpreted as the
             name of a data base (if no data base is opened) or a name 
             of an item in the opened data base.   In this case, help
             is displayed only for the particular item or database

 OUTPUTS:
      None
 OPTIONAL INPUT KEYWORDS:
      TEXTOUT  - Used to determine output device.  If not present, the
                value of !TEXTOUT system variable is used (see TEXTOPEN )

               textout=0       Nowhere
               textout=1       if a TTY then TERMINAL using /more option
                                   otherwise standard (Unit=-1) output
               textout=2       if a TTY then TERMINAL without /more option
                                   otherwise standard (Unit=-1) output
               textout=3       <program>.prt
               textout=4       laser.tmp
               textout=5      user must open file
               textout=7      same as 3 but text is appended to <program>.prt
                               file if it already exists.
               textout = filename (default extension of .prt)

        /SORT - If set and non-zero, then the help items will be displayed
               sorted alphabetically.    If more than one database is open,
               then this keyword does nothing.
 METHOD:
       If no data base is opened then a list of data bases are
       printed, otherwise the items in the open data base are printed.

       If a string is supplied for flag and a data base is opened
       flag is assumed to be an item name.  The information for that
       item is printed along with contents in a optional file
       zdbase:dbname_itemname.hlp
       if a string is supplied for flag and no data base is opened,
       then string is assumed to be the name of a data base file.
       only information for that file is printed along with an
       optional file zdbase:dbname.hlp.
 PROCEDURES USED:
       DB_INFO(),DB_ITEM_INFO(),FIND_WITH_DEF(), TEXTOPEN, TEXTCLOSE, UNIQ()
 IDL VERSION:
       V5.3 or later (uses vectorized FDECOMP)
 HISTORY:
       Version 2  D. Lindler  Nov 1987 (new db format)
       Faster printing of title desc. W. Landsman  May 1989 
       Keyword textout added, J. Isensee, July, 1990
       Modified to work on Unix, D. Neill, ACC, Feb 1991.
       William Thompson, GSFC/CDS (ARC), 1 June 1994
               Added support for external (IEEE) representation.
       William Thompson, GSFC, 3 November 1994
               Modified to allow ZDBASE to be a path string.
       Remove duplicate database names  Wayne Landsman    December 1994
       8/17/95 jkf/acc - force lowercase filenames for .hlp files.
       Added /SORT keyword  J. Sandoval/W. Landsman     October 1998
       V5.3 version use vectorized FDECOMP   W. Landsman   February 2001
       Recognize 64 bit, unsigned integer datatypes W. Landsman September 2001
       Fix display of number of bytes with /SORT W. Landsman February 2002
       Assume since V5.2                 W. Landsman February 2002  
       Assume since V5.5                 W. Landsman

(See $IDLUTILS_DIR/goddard/pro/database/dbhelp.pro)

DBINDEX

 NAME:
       DBINDEX
 PURPOSE:
       Procedure to create index file for data base 

 CALLING SEQUENCE:     
       dbindex, [ items ]

 OPTIONAL INPUT:
       items - names or numbers of items to be index -- if not supplied,
               then all indexed fields will be processed.  

 OUTPUT:
       Index file <name>.dbx is created on disk location ZDBASE:

 OPERATIONAL NOTES:
       (1) Data base must have been previously opened for update
       by DBOPEN 

       (2) Only 18 items can be indexed at one time.   If the database has
       more than 18 items, then two separate calls to DBINDEX are needed.
 PROCEDURES CALLED:
       DBINDEX_BLK, DB_INFO(), DB_ITEM, DB_ITEM_INFO(), IEEE_TO_HOST, 
       IS_IEEE_BIG()
 HISTORY:
       version 2  D. Lindler  Nov 1987 (new db format)
       W. Landsman    added optional items parameter Feb 1989 
       William Thompson, GSFC/CDS (ARC), 30 May 1994
               Added support for external (IEEE) data format
       Test if machine is bigendian  W. Landsman     May, 1996
       Change variable name of BYTESWAP to BSWAP  W. Thompson  Mar, 1997
       Increased number of fields to 15   W. Landsman   June, 1997
       Increase number of items to 18     W. Landsman  November 1999
       Allow multiple valued (nonstring) index items W. Landsman November 2000
       Use 64 bit integers for V5.2 or later  W. Landsman February 2001
       Do not use EXECUTE() for V6.1 or later, improve efficiency 
                W. Landsman   December 2006
       Automatically enlarge .dbx file if needed, fix major bug in last
             update    W. Landsman Dec 2006
       Assume since V6.1    W. Landsman   June 2009
       Allow sorted string items   W. Landsman   October 2009

(See $IDLUTILS_DIR/goddard/pro/database/dbindex.pro)

DBINDEX_BLK

 NAME:
       DBINDEX_BLK
 PURPOSE:
       Subroutine of DBINDEX to create associated variable of correct datatype
 EXPLANATION:
       DBINDEX_BLK will offset into the file by a specified amount in 
       preparation for writing to the file.   V5.2 or later

 CALLING SEQUENCE:
       res = dbindex_blk(unit, nb, bsz, ofb, dtype)

 INPUTS:
       unit   The unit number assigned to the file.
       nb     The number of blocks to offset into the file.
       bsz    The size of each block, in bytes, to offset into the file.
       ofb    The offset into the block, in bytes.
       dtype  The IDL datatype as defined in the SIZE function

 OUTPUTS:
       res    The returned variable.  This is an associated variable.

 RESTRICTIONS:
       The file must have been previously opened.

 MODIFICATION HISTORY:
       Written by Michael R. Greason, STX, 14 June 1990.
       Converted to IDL V5.0   W. Landsman   September 1997
       Use 64 bit integer for very large databases  W. Landsman February 2001
       Added new unsigned & 64bit integer datatypes    W. Landsman July 2001

(See $IDLUTILS_DIR/goddard/pro/database/dbindex_blk.pro)

DBMATCH

 NAME:
       DBMATCH
 PURPOSE:
       Find the entry number in a database for each element of item values
 EXPLANATION:
       DBMATCH() is especially useful for finding a one-to-one 
       correspondence between entries in different databases, and thus to 
       create the vector needed for database pointers.

 CALLING SEQUENCE:
       list = DBMATCH( item, values, [ listin, /FULLSTRING ] )

 INPUTS:
       ITEM - Item name or number, scalar
       VALUES -  scalar or vector containing item values to search for.

 OPTIONAL INPUTS:
       LISTIN - list of entries to be searched.  If not supplied, or
               set to -1, then all entries are searched
 OUTPUT:
       LIST - vector of entry numbers with the same number of elements as 
               VALUES.  Contains a value of 0 wherever the corresponding item
               value was not found.

 OPTIONAL INPUT:
       /FULLSTRING - By default, one has a match if a search string is 
               included in any part of a database value (substring match).   
               But if /FULLSTRING is set, then all characters in the database
               value must match the search string (excluding leading and 
               trailing blanks).    Both types of string searches are case
               insensitive.

 NOTES:
       DBMATCH is meant to be used for items which do not have duplicate values
       in a database (e.g. catalog numbers).  If more than one entry is found
       for a particular item value, then only the first one is stored in LIST.

       When linked databases are opened together, DBMATCH can only be 
       used to search on items in the primary database.

 EXAMPLE:
       Make a vector which points from entries in the Yale Bright Star catalog
       to those in the Hipparcos catalog, using the HD number

       IDL> dbopen, 'yale_bs'            ;Open the Yale Bright star catalog
       IDL> dbext, -1, 'HD', hd          ;Get the HD numbers
       IDL> dbopen, 'hipparcos'          ;Open the Hipparcos catalog
       IDL> list = dbmatch( 'HD', HD)    ;Get entries in Hipparcos catalog 
                                         ;corresponding to each HD number.
 PROCEDURE CALLS:
       DB_ITEM, DB_ITEM_INFO(), DBEXT, DBFIND_SORT()
 REVISION HISTORY:
       Written,    W. Landsman      STX     February, 1990
       Fixed error when list in parameter used May, 1992
       Faster algorithm with sorted item when listin parameter supplied 
       Added keyword FULLSTRING,check for empty database, William Thompson, 
               GSFC, 15 March 1995
       Work for more than 32767 values, added CATCH W. Landsman   July 1997
       Change some loop variables to type LONG,  W. Landsman  July 1999
       Remove loop for substring searches (faster)  W. landsman August 1999
       Replace DATATYPE() with size(/TNAME)  W. Landsman  November 2001
       Fixed typo when search on sorted items W. Landsman February 2002
       Fixed bug from Nov 2001 where /FULLSTRING was always set.  W.L Feb 2007

(See $IDLUTILS_DIR/goddard/pro/database/dbmatch.pro)

DBOPEN

 NAME:
       DBOPEN
 PURPOSE:
       Routine to open an IDL database

 CALLING SEQUENCE:
       dbopen, name, update

 INPUTS:
       name - (Optional) name or names of the data base files to open.
               It has one of the following forms:

               'name'          -open single data base file
               'name1,name2,...,nameN' - open N files which are
                               connected via pointers.
               'name,*'        -Open the data base with all data
                               bases connected via pointers
               ''              -Interactively allow selection of
                               the data base files.

               If not supplied then '' is assumed.
               name may optionally be a string array with one name
               per element.

       update - (Optional) Integer flag specifing openning for update.
               0       - Open for read only
               1       - Open for update
               2       - Open index file for update only
               !PRIV must be 2 or greater to open a file for update.
               If a file is opened for update only a single data base
               can be specified.

 OUTPUTS:
       none

 INPUT-OUTPUT KEYWORD:
       UNAVAIL - If present, a "database doesn't exit" flag is returned
                 through it.  0 = the database exists and was opened (if
                 no other errors arose).  1 = the database doesn't exist.
                 Also if present, the error message for non-existent databases
                 is suppressed.  The action, however, remains the same.  
 SIDE EFFECTS:
       The .DBF and .dbx files are opened using unit numbers obtained by
       GET_LUN.  Descriptions of the files are placed in the common block
       DB_COM.

 PROCEDURES CALLED:
       DBCLOSE, DB_INFO(), SELECT_W, ZPARCHECK
 HISTORY:
       For IDL Version 2  W. Landsman May 1990 -- Will require further 
           modfication once SCREEN_SELECT is working
       Modified to work under Unix, D. Neill, ACC, Feb 1991.
       UNAVAIL keyword added.  M. Greason, Hughes STX, Feb 1993.
       William Thompson, GSFC/CDS (ARC), 1 June 1994
               Added support for external (IEEE) representation.
       William Thompson, GSFC, 3 November 1994
                       Modified to allow ZDBASE to be a path string.
       8/29/95 JKF/ACC - forces lowercase for input database names.
       W. Landsman, Use CATCH to catch errors    July, 1997
       W. Landsman Use vector call to FDECOMP, STRSPLIT()    Sep 2006
       W. Landsman Remove obsolete keywords to OPEN   Sep 2006
       Replace SCREEN_SELECT with SELECT_W, remove IEEE_TO_HOST  WL  Jan 2009
       Fix typos in BYTEORDER introduced Jan 2009 G. Scandariato/W.L.Feb. 2009
       Support new DB format which allows entry lengths > 32767 bytes 
              W.L. October 2010
       William Thompson, fixed bug opening multiple databases Dec 2010
       Fix problem with external databases WL Sep 2011

(See $IDLUTILS_DIR/goddard/pro/database/dbopen.pro)

DBPRINT

 NAME:
     DBPRINT
 PURPOSE:
     Procedure to print specified items from a list of database entries

 CALLING SEQUENCE:     
     dbprint, list, [items, FORMS= , TEXTOUT= , /AdjustFormat, /NoHeader]  

 INPUTS:
     list  - list of entry numbers to be printed, vector or scalar 
               if list = -1, then all entries will be printed.
               An error message is returned if any entry number is larger
               than the number of entries in the database

 OPTIONAL INPUT-OUTPUT:
     items - items to be printed, specified in any of the following ways:

               form 1  scalar string giving item(s) as list of names
                       separated by commas
               form 2  string array giving list of item names
               form 3  string of form '$filename' giving name
                       of text file containing items (one item per
                       line)
               form 4  integer scalar giving single item number or
                         integer vector list of item numbers
               form 5  Null string specifying interactive selection.   This
                       is the default if 'items' is not supplied
               form 6  '*'     select all items, printout will be in
                       table format. 

            If items was undefined or a null string on input, then
            on output it will contain the items interactively selected.

 OPTIONAL INPUT KEYWORDS:
       /ADJUSTFORMAT -  If set, then the format length for string items will
               be adjusted to the maximum length for the entries to be printed.
               This option will slow down DBPRINT because it requires the 
               string items be extracted and their maximum length determined 
               prior to any printing.   However, it enables the display of
               string items without any truncation or wasted space. 

       FORMS - The number of printed lines per page. If forms is not 
               present, output assumed to be in PORTRAIT form, and 
               a heading and 47 lines are printed on each page, with
               a page eject between each page.  For LANDSCAPE form with
               headings on each page, and a page eject between pages, set 
               forms = 34.  For a heading only on the first page, and no
               page eject, set forms = 0.   This is the default for output
               to the terminal.

       TEXTOUT - Integer (0-7) or string used to determine output device (see 
               TEXTOPEN for more info).  If not present, the !TEXTOUT system 
               variable is used.
               textout=0       Nowhere
               textout=1       if a TTY then TERMINAL using /more option
                                   otherwise standard (Unit=-1) output
               textout=2       if a TTY then TERMINAL without /more option
                                   otherwise standard (Unit=-1) output
               textout=3       dbprint.prt (file)
               textout=4       laser.tmp
               textout=5       user must open file
               textout=7      same as 3 but text is appended to <program>.prt
               textout = filename   (default extension of .prt)

       /NOHEADER - If this keyword is set, then the column headers will not
               be printed

 EXAMPLE:
       The following example shows how a multiple valued item DATAMAX can be 
       printed as separate columns.   In the WFPC2 target database, DATAMAX
       is an item with 4 values, one for each of the 4 chips

       IDL> dbopen,'wflog'
       IDL> dbprint,list,'entry,datamax(0),datamax(1),datamax(2),datamax(3)'

 SYSTEM VARIABLES:
       Output device controlled by non-standard system varaible !TEXTOUT, if 
       TEXTOUT keyword is not used.    

 NOTES:
       Users may want to adjust the default lines_per_page value given at
       the beginning of the program for their own particular printer.
 PROCEDURE CALLS:
       db_info(), db_item_info(), dbtitle(), dbxval(), textopen, textclose
       zparcheck
 HISTORY:
       version 2  D. Lindler  Nov. 1987 (new db format)
       Test if user pressed 'Q' in response to /MORE W. Landsman  Sep 1991
       Apply STRTRIM to free form (table) output    W. Landsman   Dec 1992
       Test for string value of TEXTOUT         W. Landsman   Feb 1994
       William Thompson, GSFC, 3 November 1994
                       Modified to allow ZDBASE to be a path string.
       W. Landsman, GSFC, July, 1997, Use CATCH to catch errors
       Removed STRTRIM in table format output to handle byte values April 1999
       Fixed occasional problem when /NOHEADER is supplied   Sep. 1999
       Only byteswap when necessary for improved performance  Feb. 2000
       Change loop index for table listing to type LONG  W. Landsman Aug 2000
       Entry vector can be any integer type   W. Landsman Aug. 2001
       Replace DATATYPE() with size(/TNAME)   W. Landsman  Nov. 2001
       No page eject for TEXTOUT =5           W. Landsman  Nov. 2001
       No initial page eject                  W. Landsman  Jan. 2002
       Added AdjustFormat keyword             W. Landsman  Sep. 2002
       Assume since V5.3 (STRJOIN)            W. Landsman Feb. 2004
       Fix display on GUI terminals           W. Landsman March 2006
       Remove VMS statements                  W. Landsman Sep 2006
       Remove EXECUTE statement               W. Landsman Jan 2007
       Fix display of multi element items     W. Landsman  Aug 2010
       Fix problem with linked databases      W. Landsman Dec 2011

(See $IDLUTILS_DIR/goddard/pro/database/dbprint.pro)

DBPUT

 NAME:
	DBPUT
 PURPOSE:
	Procedure to place a new value for a specified item into
	a data base file entry.  

 CALLING SEQUENCE:	
	dbput, item, val, entry

 INPUTS:
	item - item name or number
	val - item value(s)

 INPUT/OUTPUT:
	entry - entry (byte array) or scalar entry number.
	        if entry is a scalar entry number then the data
	        base file will be updated.  Otherwise the change
	        will be only made to the entry array which must
	        be written latter using DBWRT.

 OPERATIONAL NOTES:
	If entry is a scalar entry number or the input file name
	is supplied, the entry in the data base will be updated
	instead of a supplied entry variable.  In this case, !priv
	must be greater than 1.
 EXAMPLE:
       IDL> dbput,'WAVELEN',1215.6,entry
 PROCEDURES USED:
       DB_ITEM, DBRD, DBXPUT, DBWRT
 HISTORY:
	version 2  D. Lindler  Feb 1988 (new db formats)
	modified to convert blanks into zeros correctly D. Neill Jan 1991
	Converted to IDL V5.0   W. Landsman   September 1997
       V5.2 version support unsigned, 64bit integers W. Landsman  Sep. 2001

(See $IDLUTILS_DIR/goddard/pro/database/dbput.pro)

DBRD

 NAME:
	DBRD
 PURPOSE:
	procedure to read an entry from a data base file or from
	linked multiple databases.

 CALLING SEQUENCE:
	dbrd, enum, entry, [available, dbno, /NoConvert]

 INPUTS:
	enum - entry number to read, integer scalar

 OUTPUT:
	entry - byte array containing the entry

 OPTIONAL OUTPUT:
	available - byte array with length equal to number of data
		bases opened.  available(i) eq 1 if an entry (pointed
		to) is available.  It always equals 1 for the first 
		data base, otherwise it is an error condition.

 OPTIONAL  INPUT:
	dbno - specification of the data base number to return.  If
		supplied, only the record for the requested data base
		number is returned in entry.  Normally this input should
		not be supplied.  dbno is numbered for 0 to n-1 and gives
		the number of the data base opened.  The data bases are 
		numbered in the order supplied to dbopen.  If dbno is supplied 
		then the entry number refers to that data base and not the
		primary or first data base. If set to -1, then it means all
		data bases opened (same as not supplying it)
 OPTIONAL INPUT KEYWORD:
	noconvert - if set then don't convert external to host format.
		Assumes that calling program will take care of this
		requirement.
 OPERATIONAL NOTES:
	If multiple data base files are opened, the records are
	concatenated with each other
 HISTORY
	version 2  D. Lindler  Nov. 1987
	William Thompson, GSFC/CDS (ARC), 1 June 1994
		Added support for external (IEEE) representation.
	Version 3, Richard Schwartz, GSFC/SDAC, 23-Aug-1996
			Add noconvert keyword

	Converted to IDL V5.0   W. Landsman   September 1997
       Version 4, 2 May 2003, W. Thompson
               Use BSWAP keyword to DBXVAL instead of calling IEEE_TO_HOST.

(See $IDLUTILS_DIR/goddard/pro/database/dbrd.pro)

DBSEARCH

 NAME:
	DBSEARCH
 PURPOSE:
	Subroutine of DBFIND() to search a vector for specified values

 CALLING SEQUENCE:
	dbsearch, type, svals, values, good, [ /FULLSTRING, COUNT = ] 

 INPUT: 
	type - type of search (output from dbfparse)
	svals - search values (output from dbfparse)
	values - array of values to search

 OUTPUT:
	good - indices of good values

 OPTIONAL INPUT KEYWORD:
	/FULLSTRING - By default, one has a match if a search string is 
		included in any part of a database value (substring match).   
		But if /FULLSTRING is set, then all characters in the database
		value must match the search string (excluding leading and 
		trailing blanks).    Both types of string searches are case
		insensitive.
 OPTIONAL OUTPUT KEYWORD:
       COUNT  - Integer scalar giving the number of valid matches
  SIDE EFFECTS:
	The obsolete system variable !ERR is set to number of good values
 REVISION HISTORY:
	D. Lindler  July,1987
       Added COUNT keyword, deprecate !ERR   W. Landsman   March 2000
      Some speed improvements W.L. August 2008
       Add compound operators, slightly faster WL November 2009

(See $IDLUTILS_DIR/goddard/pro/database/dbsearch.pro)

DBSORT

 NAME:
       DBSORT
 PURPOSE:
       Routine to sort list of entries in data base

 CALLING SEQUENCE: 
       result = dbsort( list, items , [ REVERSE = ])

 INPUTS:
       list - list of entry numbers to sort
               -1 to sort all entries
       items - list of items to sort (up to 9 items)

 OUTPUT:
       result - numeric vector giving input list sorted by items

 OPTIONAL KEYWORD INPUT:
       REVERSE - scalar or vector with the same number of elements as the
         the number of items to sort.  If the corresponding element of REVERSE 
         is non-zero then that item is sorted in descending rather than 
         ascending order.

 EXAMPLE:
       Sort an astronomical catalog with RA as primary sort, and declination
       as secondary sort (used when RA values are equal)

          IDL> NEWLIST = DBSORT( -1, 'RA,DEC' )

       If for some reason, one wanted the DEC sorted in descending order, but
       the RA in ascending order

          IDL> NEWLIST = DBSORT( -1, 'RA,DEC', REV = [ 0, 1 ] )

 METHOD:
       The list is sorted such that each item is sorted into
       asscending order starting with the last item.
 COMMON BLOCKS:
       DBCOM
 PROCEDURES USED:
       ZPARCHECK, BSORT, DBEXT, DB_ITEM
 HISTORY
       VERSION 1  D. Lindler  Oct. 86
       Added REVERSE keyword   W. Landsman        August, 1991
       Avoid use of EXECUTE() for V6.1 or later   W. Landsman Dec 2006
       Assume since V6.1   W. Landsman   June 2009
       Add TEMPORARY call  W. Lnadsman  July 2009

(See $IDLUTILS_DIR/goddard/pro/database/dbsort.pro)

DBTARGET

 NAME:
      DBTARGET
 PURPOSE:
      Find sources in a database within specified radius of specified target
 EXPLANATION:
      Uses QuerySimbad to translate target name to RA and Dec, and then uses
      DBCIRCLE() to find any entries within specified radius.   Database must 
      include items named 'RA' (in hours) and 'DEC' (in degrees) and must 
      have previously been opened with DBOPEN

 CALLING SEQUENCE:
     list = DBTARGET(target, [radius, sublist, /SILENT, DIS= ,/TO_B1950 ] )   

 INPUTS:
      TARGET - A scalar string giving an astronomical target name, which 
          will be  translated into J2000 celestial coordinates by QuerySimbad 

 OPTIONAL INPUT:
       RADIUS - Radius of the search field in arc minutes, scalar.
                Default is 5 arc minutes
       SUBLIST - Vector giving entry numbers in currently opened database
               to be searched.  Default is to search all entries

 OUTPUTS:
     LIST - Vector giving entry numbers in the currently opened catalog
            which have positions within the specified search circle
            LIST is set to -1 if no sources fall within the search circle
            !ERR is set to the number sources found.

 OPTIONAL OUTPUT
       DIS -  The distance in arcminutes of each entry specified by LIST
               to the search center specified by the target.

 OPTIONAL KEYWORD INPUT:
       /SILENT - If this keyword is set, then DBTARGET will not print the 
               number of entries found at the terminal
       /TO_B1950 - If this keyword is set, then the SIMBAD J2000 coordinates 
               are converted to B1950 before searching the database
               NOTE: The user must determine on his own whether the database
               is in B1950 or J2000 coordinates.

 RESTRICTIONS;
       The database must have items 'RA' (in hours) and 'DEC' (in degrees).
       Alternatively, the database could have items RA_OBJ and DEC_OBJ 
      (both in degrees)
 EXAMPLE:
       (1) Use the HST_CATALOG database to find all  HST observations within 
           5' (the default) of M33

       IDL> dbopen,'hst_catalog'
       IDL> list = dbtarget('M33')

      (2) As above but restrict targets within 2' of the nucleus using the
          WFPC2 camara

       IDL> dbopen,'hst_catalog'
       IDL> sublist = dbfind('config=WFPC2')
       IDL> list = dbtarget('M33',2,sublist)


 PROCEDURE CALLS:
       QuerySimbad, DBCIRCLE()
 REVISION HISTORY:
      Written W. Landsman     SSAI          September 2002
      Propagate /SILENT keyword to QuerySimbad    W. Landsman Oct 2009
      Make sure a database is open  W.L. Oct 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbtarget.pro)

DBTITLE

 NAME:
	DBTITLE
 PURPOSE:
	function to create title line for routine dbprint

 CALLING SEQUENCE:
	result = dbtitle( c, f )

 INPUTS:
	c = string array of titles for each item
	f = field length of each item

 OUTPUT:
	header string returned as function value

 OPERATIONAL NOTES:
	this is a subroutine of DBPRINT.

 HISTORY:
	version 1  D. Lindler  Sept 86
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/database/dbtitle.pro)

DBUPDATE

 NAME:
	DBUPDATE
 PURPOSE:
	Update columns of data in a database  -- inverse of DBEXT
 EXPLANATION:
	Database must be open for update before calling DBUPDATE

 CALLING SEQUENCE:
	dbupdate, list, items, v1, [ v2, v3, v4......v14 ]

 INPUTS:
	list - entries in database to be updated, scalar or vector
		If list=-1 then all entries will be updated
	items -standard list of items that will be updated.  
	v1,v2....v14 - vectors containing values for specified items.  The
		number of vectors supplied must equal the number of items
		specified.   The number of elements in each vector should be
		the same.

 OPTIONAL KEYWORD INPUT:
       /NOINDEX - If set, then DBUPDATE will not update the index file.   This
               keyword is useful to save if additional updates will occur,
               and the index file need only be updated on the last call.
            
 EXAMPLES:
	A database STAR contains RA and DEC in radians, convert to degrees

	IDL> !PRIV=2 & dbopen,'STAR',1          ;Open database for update
	IDL> dbext,-1,'RA,DEC',ra,dec          ;Extract RA and DEC, all entries 
	IDL> ra = ra*!RADEG & dec=dec*!RADEG    ;Convert to degrees
	IDL> dbupdate,-1,'RA,DEC',ra,dec        ;Update database with new values

 NOTES:
	It is quicker to update several items simultaneously rather than use
	repeated calls to DBUPDATE.  
 
	It is possible to update multiple valued items.  In this case, the
	input vector should be of dimension (NVAL,NLIST) where NVAL is the
	number of values per item, and NLIST is the number of entries to be
	updated.  This vector will be temporarily transposed by DBUPDATE but
	will be restored before DBUPDATE exits.

 REVISION HISTORY
	Written W. Landsman      STX       March, 1989
	Work for multiple valued items     May, 1991
	String arrays no longer need to be fixed length      December 1992
	Transpose multiple array items back on output        December 1993
	Faster update of external databases on big endian machines November 1997
	Converted to IDL V5.0   W. Landsman 24-Nov-1997
       Added /NOINDEX keyword  W. Landsman  July 2001

(See $IDLUTILS_DIR/goddard/pro/database/dbupdate.pro)

DBVAL

 NAME:
	DBVAL
 PURPOSE:
	procedure to extract value(s) of the specified item from
	a data base file entry.

 CALLING SEQUENCE:
	result = dbval( entry, item )

 INPUTS:
	entry - byte array containing the entry, or a scalar entry number
	item - name (string) or number (integer) of the item

 OUTPUT:
	the value(s) will be returned as the function value

 EXAMPLE:
	Extract a flux vector from entry 28 of the database FARUV
	==> flux = dbval(28,'FLUX')

 HISTORY:
   version 2  D. Lindler Nov, 1987	(new db format)
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/database/dbval.pro)

DBWRT

 NAME:
	DBWRT
 PURPOSE:
	procedure to update or add a new entry to a data base

 CALLING SEQUENCE:
	dbwrt, entry, [ index, append, /NoConvert ]

 INPUTS:
	entry - entry record to be updated or added if first
		item (entry number=0)

 OPTIONAL INPUTS:
	index - optional integer flag,  if set to non zero then index
		file is  updated. (default=0, do not update index file)
		(Updating the index file is time-consuming, and should
		normally be done after all changes have been made.
	append - optional integer flag, if set to non-zero the record
		is appended as a new entry, regardless of what the
		entry number in the record is.  The entry number will
		be reset to the next entry number in the file.
 OUTPUTS:
	data base file is updated.                    
	If index is non-zero then the index file is updated.
 OPTIONAL INPUT KEYWORD:
	NoConvert - If set then don't convert to host format with an external
		database.    Useful when the calling program decides that
		conversion isn't needed (i.e. on a big-endian machine), or 
		takes care of the conversion itself.
 OPERATIONAL NOTES:
	!PRIV must be greater than 1 to execute
 HISTORY:
	version 2  D. Lindler  Feb. 1988 (new db format)
	converted to IDL Version 2.  M. Greason, STX, June 1990.
	William Thompson, GSFC/CDS (ARC), 28 May 1994
		Added support for external (IEEE) representation.
	Faster handling of byte swapping  W. L.  August 2010

(See $IDLUTILS_DIR/goddard/pro/database/dbwrt.pro)

DBXPUT

 NAME:
	DBXPUT
 PURPOSE:
	routine to replace value of an item in a data base entry

 CALLING SEQUENCE:	
	dbxput, val, entry, idltype, sbyte, nbytes

 INPUT:
	val - value(s) to be placed into entry, string values might be
		truncated to fit number of allowed bytes in item
	entry - entry or entries to be updated
	idltype - idl data type for item (1-7)
	sbyte - starting byte in record
	nbytes - total number of bytes in value added

 OUTPUT:
	entry - (updated)

 OPERATIONAL NOTES:
	This routine assumes that the calling procedure or user knows what he 
	or she is doing.  String items are truncated or padded to the fixed 
	size specified by the database but otherwise no validity checks are 
	made.

 HISTORY:
	version 1, D. Lindler   Aug, 1986
	converted to IDL Version 2.  M. Greason, STX, June 1990.
	Work with multiple element string items   W. Landsman  August 1995
	Really work with multiple element string items   
			R. Bergman/W. Landsman  July 1996
	Work with multiple entries, R. Schwartz, GSFC/SDAC August 1996
	Use /overwrite with REFORM() W. Landsman May 1997
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/database/dbxput.pro)

DBXVAL

 NAME: 
       DBXVAL

 PURPOSE:      
       Quickly return a value of the specified item number     
 EXPLANATION:
       Procedure to quickly return a value of the specified item number
       from the entry.

 CALLING SEQUENCE:     
       result = dbxval( entry, idltype, nvalues, sbyte, nbytes )

 INPUTS        
       entry - entry or entries from data base (bytarr) 
       idltype - idl data type (obtained with db_item_info)
       nvalues - number of values to return (obtained with db_item)
       sbyte - starting byte in the entry (obtained with db_item)
       nbytes - number of bytes (needed only for string type)
                       (obtained with db_item)

 OUTPUTS:      
       function value is value of the specified item in entry

 KEYWORDS:
       bswap - If set, then IEEE_TO_HOST is called.

 RESTRICTIONS: 
       To increase speed the routine assumes that entry and item are
       valid and that the data base is already opened using dbopen.

 REVISION HISTORY:     
       version 0  D. Lindler Nov. 1987  (for new db format)
       Version 1, William Thompson, GSFC, 28 March 1994.
                       Incorporated into CDS library.
       Version 2, Richard Schwartz, GSFC/SDAC, 23 August 1996
                       Allowed Entry to have 2 dimensions
       Version 2.1, 22 Feb 1997, JK Feggans, 
                               avoid reform for strings arrays.
       Version 2.2     Use overwrite with REFORM(),  W. Landsman,  May 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Work for multiple-valued strings   W. Landsman   October 2000
       Add new 64bit & unsigned integer datatypes W.Landsman   July 2001
       Version 3, 2-May-2003, JK Feggans/Sigma, W.T. Thompson
           Added BSWAP keyword to avoid floating errors on some platforms.

(See $IDLUTILS_DIR/goddard/pro/database/dbxval.pro)

DB_ENT2EXT

 NAME:
	DB_ENT2EXT
 PURPOSE:
	Convert a database entry to external (IEEE) data format
 EXPLANATION: 
	Converts a database entry to external (IEEE) data format prior to
	writing it.  Called from DBWRT.

 CALLING SEQUENCE:
	DB_ENT2EXT, ENTRY

 INPUTS:
	ENTRY	= Byte array containing a single record to be written to the
		  database file.

 OUTPUTS:
	ENTRY	= The converted array is returned in place of the input array.

 COMMON BLOCKS:
	DB_COM

 HISTORY:
	Version 1, William Thompson, GSFC/CDS (ARC), 1 June 1994
	Version 2, William Thompson, GSFC/CDS (ARC), 15 September 1995
			Fixed bug where only the first element in a
			multidimensional array was converted.
       Version 2.1 W. Landsman August 2010 Fix for multidimensional strings
       Version 2.2 W. Landsman Sep 2011 Work with new DB format

(See $IDLUTILS_DIR/goddard/pro/database/db_ent2ext.pro)

DB_ENT2HOST

 NAME:
	DB_ENT2HOST
 PURPOSE:
	Converts a database entry from external data format to host format.
 EXPLANATION:
	All items are extracted from the entry, and then converted to host 
	format, and placed back into the entry.  Called from DBRD and DBEXT_DBF.

 CALLING SEQUENCE:
	DB_ENT2HOST, ENTRY, DBNO

 INPUTS:
	ENTRY	= Byte array containing a single record read from the
		  database file.
	DBNO	= Number of the opened database file.

 OUTPUTS:
	ENTRY	= The converted array is returned in place of the input array.

 COMMON BLOCKS:
	DB_COM

 HISTORY:
	Version 1, William Thompson, GSFC/CDS (ARC), 1 June 1994
	Version 2, William Thompson, GSFC/CDS (ARC), 15 September 1995
			Fixed bug where only the first element in a
			multidimensional array was converted.
	Version 3, Richard Schwartz, GSFC/SDAC, 23 August 1996
		Allow 2 dimensional byte arrays for entries to facilitate 
		multiple entry processing.    Pass IDLTYPE onto IEEE_TO_HOST
       Version 4, 2 May 2003, W. Thompson
               Use BSWAP keyword to DBXVAL instead of calling IEEE_TO_HOST.
       Version 4.1 W. Landsman August 2010 Fix for multidimensional strings
       Version 4.2 W. Landsman Sep 2011 Work with new DB format

(See $IDLUTILS_DIR/goddard/pro/database/db_ent2host.pro)

DB_INFO

 NAME:
       DB_INFO
 PURPOSE:
       Function to obtain information on opened data base file(s)

 CALLING SEQUENCES:
       1)  result = db_info(request)
       2)  result = db_info(request,dbname)
 INPUTS (calling sequence 1):

       request - string specifying requested value(s)
               value of request          value returned in result
                       'open'          Flag set to 1 if data base(s) are opened
                       'number'        Number of data base files opened
                       'items'         Total number of items (all db's opened)
                       'update'        update flag (1 if opened for update)
                       'unit_dbf'      Unit number of the .dbf files
                       'unit_dbx'      Unit number of the .dbx files
                       'entries'       Number of entries in the db's
                       'length'        Record lengths for the db's
                       'external'      True if the db's are in external format

 INPUTS (calling sequence 2):

       request - string specifying requested value(s)
                  value of request       value returned in result
                       'name'          Name of the data base
                       'number'        Sequential number of the db
                       'items'         Number of items for this db
                       'item1'         Position of item1 for this db
                                       in item list for all db's
                       'item2'         Position of last item for this db.
                       'pointer'       Number of the item which points
                                       to this db. 0 for first or primary
                                       db.  -1 if link file pointers.
                       'length'        Record length for this db.
                       'title'         Title of the data base
                       'unit_dbf'      Unit number of the .dbf file
                       'unit_dbx'      Unit number of the .dbx file
                       'entries'       Number of entries in the db
                       'seqnum'        Last sequence number used
                       'alloc'         Allocated space (# entries)
                       'update'        1 if data base opened for update
                       'external'      True if data base in external format
                       'newdb'         True if new (post Oct 2010) format 
                                       that allows entries > 32767 bytes

       dbname - data base name or number
 OUTPUTS:
       Requested value(s) are returned as the function value.

 HISTORY:
       version 1  D. Lindler    Oct. 1987
       changed type from 1 to 7 for IDLV2, J. Isensee, Nov., 1990
       William Thompson, GSFC/CDS (ARC), 30 May 1994
               Added EXTERNAL request type.
       Support new DB format, add NEWDB request type W. Landsman Oct 2010

(See $IDLUTILS_DIR/goddard/pro/database/db_info.pro)

DB_ITEM

 NAME: 
       DB_ITEM
 PURPOSE:      
       Returns the item numbers and other info. for an item name.
 EXPLANATION:  
       Procedure to return the item numbers and other information
       of a specified item name

 CALLING SEQUENCE:     
       db_item, items, itnum, ivalnum, idltype, sbyte, numvals, nbytes

 INPUTS:       
       items - item name or number
               form 1  scalar string giving item(s) as list of names
                       separated by commas
               form 2  string array giving list of item names
               form 3  string of form '$filename' giving name
                       of text file containing items (one item per
                       line)
               form 4  integer scalar giving single item number or
                         integer vector list of item numbers
               form 5  Null string specifying interactive selection
                       Upon return items will contain selected items
                       in form 1
               form 6  '*'     select all items

 OUTPUTS:      
       itnum - item number
       ivalnum - value(s) number from multiple valued item
       idltype - data type(s) (1=string,2=byte,4=i*4,...)
       sbyte - starting byte(s) in entry
       numvals - number of data values for item(s)
               It is the full length of a vector item unless
               a subscript was supplied
       nbytes - number of bytes for each value
    All outputs are vectors even if a single item is requested

 OPTIONAL INPUT KEYWORDS:      
       ERRMSG   = If defined and passed, then any error messages will
               be returned to the user in this parameter rather than depending
               on the MESSAGE routine in IDL.  If no errors are encountered, 
               then a null string is returned.  In order to use this feature, 
               ERRMSG must be defined first, e.g.

                               ERRMSG = ''
                               DB_ITEM, ERRMSG=ERRMSG, ...
                               IF ERRMSG NE '' THEN ...

 PROCEDURE CALLS:
       DB_INFO, GETTOK, SELECT_W

 REVISION HISTORY:
       Written:   D. Lindler, GSFC/HRS, October 1987
       Version 2, William Thompson, GSFC, 17-Mar-1997
                       Added keyword ERRMSG
       Use STRSPLIT instead of GETTOK to parse form 1, W. Landsman July 2002
       Assume since V5.4 use FILE_EXPAND_PATH() instead of SPEC_DIR()
               W. Landsman April 2006
       Support new DB format allowing entry lengths > 32767 bytes WL Oct 2010
       Ignore blank lines in .items file WL February 2011

(See $IDLUTILS_DIR/goddard/pro/database/db_item.pro)

DB_ITEM_INFO

 NAME:
	DB_ITEM_INFO
 PURPOSE:
	routine to return information on selected item(s) in the opened
	data bases.

 CALLING SEQUENCE:
	result = db_item_info( request, itnums)
 INPUTS:
	request - string giving the requested information.
		'name'		- item names
		'idltype'	- IDL data type (integers)
				  see documentation of intrinsic SIZE funtion
		'nvalues'	- vector item length (1 for scalar)
		'sbyte'		- starting byte in .dbf record (use bytepos
				  to get starting byte in record returned by
				  dbrd)
		'nbytes'	- bytes per data value
		'index'		- index types
		'description'	- description of the item
		'pflag'		- pointer item flags
		'pointer'	- data bases the items point to
		'format'	- print formats
		'flen'		- print field length
		'headers'	- print headers
		'bytepos'	- starting byte in dbrd record for the items
		'dbnumber'	- number of the opened data base
		'pnumber'	- number of db it points to (if the db is
					opened)
		'itemnumber'	- item number in the file

	itnums -(optional) Item numbers.  If not supplied info on all items
		are returned.
 OUTPUT:
	Requested information is returned as a vector.  Its type depends
	on the item requested.
 HISTORY:
	version 1  D. Lindler  Nov. 1987
	Converted to IDL V5.0   W. Landsman   September 1997
       Support new DB format which allows > 32767 bytes W.L. Oct 2010

(See $IDLUTILS_DIR/goddard/pro/database/db_item_info.pro)

DB_OR

 NAME:
	DB_OR
 PURPOSE:
	Combine two vectors of entry numbers, removing duplicate values.
 EXPLANATION:
	DB_OR can also be used to remove duplicate values from any longword 
	vector

 CALLING SEQUENCE:
	LIST = DB_OR( LIST1 )          ;Remove duplicate values from LIST1
		or
	LIST = DB_OR( LIST1, LIST2 )   ;Concatenate LIST1 and LIST2, remove dups

 INPUTS:
	LIST1, LIST2 - Vectors containing entry numbers, must be non-negative
			integers or longwords.
 OUTPUT:
	LIST - Vector containing entry numbers in either LIST1 or LIST2
  
 METHOD
	DB_OR returns where the histogram of the entry vectors is non-zero

 PROCEDURE CALLS
	ZPARCHECK - checks parameters  
 REVISION HISTORY:
	Written,     W. Landsman             February, 1989
	Check for degenerate values  W.L.    February, 1993
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/database/db_or.pro)

DB_TITLES

 NAME:
	DB_TITLES

 PURPOSE:
	Print database name and title.  Called by DBHELP

 CALLING SEQUENCE:
	db_titles, fnames, titles

 INPUT:
	fnames - string array of data base names

 SIDE EFFECT:
	Database name is printed along with the description in the .dbh file

 HISTORY:
	version 2  W. Landsman May, 1989
	modified to work under Unix, D. Neill, ACC, Feb 1991.
	William Thompson, GSFC/CDS (ARC), 1 June 1994
		Added support for external (IEEE) representation.
	William Thompson, GSFC, 3 November 1994
			Modified to allow ZDBASE to be a path string.
	Converted to IDL V5.0   W. Landsman   September 1997
       Assume since V5.5,      W. Landsman   September 2006

(See $IDLUTILS_DIR/goddard/pro/database/db_titles.pro)

DECOMPOSEDCOLOR

NAME:
DECOMPOSEDCOLOR

PURPOSE:

This function is used to determine, in a device independent way, if the
current graphics device is using color decomposition. The function returns
a 1 if color decomposition is turned on, and a 0 if it is turned off. When
color decomposition is turned on, we say the device is using a true-color
display. If color decomposition is turned off, we say the device is using
an indexed color display.

AUTHOR:

FANNING SOFTWARE CONSULTING
David Fanning, Ph.D.
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: david@idlcoyote.com
Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

CATEGORY:

Utilities

CALLING SEQUENCE:

result = DecomposedColor()

RETURN VALUE:

result: A 1 if color decomposition is turned on. A 0 if color decomposition is turned off.

ARGUMENTS:

device: The IDL graphics device whose color decomposition state you wish to know the
current value of. If undefined, the current graphics device is used.

KEYWORDRS:

DEPTH: An output keyword that returns the depth of the graphics device. Normally,
either 8 for index color devices, with color decomposition turned off, or 24
for true-color devices with color decomposition turned on.

EXAMPLE:

IDL> Print, DecomposedColor() ; Color decomposition state of current graphics device.
1
IDL> Print, DecomposedColor('PS') ; Color decomposition state of PostScript graphics device.
0

MODIFICATION HISTORY:

Written by: David W. Fanning, May 24, 2009.
Modified the way decomposition was obtained for PostScript devices IDL 7.1 and higher. 12 Dec 2010. DWF.
Fixed a problem in the CASE statement with ELSE clause and added a NULL device segment. 4 Jan 2011. DWF.
It now appears 24-bit PostScript support was added in IDL 7.1, although the Get_Decomposed keyword
didn't work until IDL 7.1.1. 13 January 2011. DWF

(See $IDLUTILS_DIR/goddard/pro/coyote/decomposedcolor.pro)

DELVARX

 NAME: 
	DELVARX
 PURPOSE: 
 	Delete up to 10 variables for memory management (can call from routines) 
 EXPLANATION:
	Like intrinsic DELVAR function, but can be used from any calling level
   
       Modified in January 2012 to always free memory associated with
       pointers/objects and remove the use EXECUTE()
 CALLING SEQUENCE:
 	DELVARX,  p0, [p1, p2......p9]

 INPUTS: 
	p0, p1...p9 - variables to delete

 OBSOLETE KEYWORD:
       /FREE_MEM -  formerly freed memory associated with pointers 
                   and objects.  Since this is now the DELVARX default this 
                   keyword does nothing.   
           
 METHOD: 
	Uses HEAP_FREE and PTR_NEW(/NO_COPY) to delete variables and free
       memory   

 REVISION HISTORY:
	Copied from the Solar library, written by slf, 25-Feb-1993
	Added to Astronomy Library,  September 1995
       Modified, 26-Mar-2003, Zarro (EER/GSFC) 26-Mar-2003
       - added FREE_MEM to free pointer/objects
       Modified, 28-Jan-2012, E. Rykoff (SLAC), W. Landsman - 
               replace EXECUTE calls with SCOPE_VARFETCH.

(See $IDLUTILS_DIR/goddard/pro/misc/delvarx.pro)

DEREDD

 NAME:
     DEREDD

 PURPOSE:
     Deredden stellar Stromgren parameters given for a value of E(b-y)
 EXPLANATION:
     See the procedure UVBYBETA for more info.

  CALLING SEQUENCE:
     deredd, eby, by, m1, c1, ub, by0, m0, c0, ub0, /UPDATE

  INPUTS:
     Eby - color index E(b-y),scalar  (E(b-y) = 0.73*E(B-V) )
     by - b-y color (observed)
     m1 - Stromgren line blanketing parameter (observed)
     c1 - Stromgren Balmer discontinuity parameter (observed)
     ub - u-b color (observed)

     These input values are unaltered unless the /UPDATE keyword is set
  OUTPUTS:
     by0 - b-y color (dereddened)
     m0 - Line blanketing index (dereddened)
     c0 - Balmer discontinuity parameter (dereddened)
     ub0 - u-b color (dereddened)

  OPTIONAL INPUT KEYWORDS:
     /UPDATE - If set, then input parameters are updated with the dereddened
           values (and output parameters are not used).
  REVISION HISTORY:
     Adapted from FORTRAN routine DEREDD by T.T. Moon 
     W. Landsman          STX Co.        April, 1988
     Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/deredd.pro)

DETABIFY

 NAME:
	DETABIFY
 PURPOSE:
	Replaces tabs in character strings with appropriate number of spaces
 EXPLANATION:
	The number of space characters inserted is calculated to space
	out to the next effective tab stop, each of which is eight characters
	apart.

 CALLING SEQUENCE:
	Result = DETABIFY( CHAR_STR )

 INPUT PARAMETERS:
	CHAR_STR = Character string variable (or array) to remove tabs from.

 OUTPUT:
	Result of function is CHAR_STR with tabs replaced by spaces.

 RESTRICTIONS:
	CHAR_STR must be a character string variable.

 MODIFICATION HISTORY:
	William Thompson, Feb. 1992.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/detabify.pro)

DIST_CIRCLE

 NAME: 
      DIST_CIRCLE
 PURPOSE:      
      Form a square array where each value is its distance to a given center.
 EXPLANATION:
      Returns a square array in which the value of each element is its 
      distance to a specified center. Useful for circular aperture photometry.

 CALLING SEQUENCE:
      DIST_CIRCLE, IM, N, [ XCEN, YCEN,  /DOUBLE ]

 INPUTS:
      N = either  a scalar specifying the size of the N x N square output
               array, or a 2 element vector specifying the size of the
               N x M rectangular output array.

 OPTIONAL INPUTS:
      XCEN,YCEN = Scalars designating the X,Y pixel center.  These need
               not be integers, and need not be located within the
               output image.   If not supplied then the center of the output
               image is used (XCEN = YCEN = (N-1)/2.).

 OUTPUTS:
       IM  - N by N (or M x N) floating array in which the value of each 
               pixel is equal to its distance to XCEN,YCEN

 OPTIONAL INPUT KEYWORD:
       /DOUBLE - If this keyword is set and nonzero, the output array will
               be of type DOUBLE rather than floating point.

 EXAMPLE:
       Total the flux in a circular aperture within 3' of a specified RA
       and DEC on an 512 x 512 image IM, with a header H.

       IDL> adxy, H, RA, DEC, x, y       ;Convert RA and DEC to X,Y
       IDL> getrot, H, rot, cdelt        ;CDELT gives plate scale deg/pixel
       IDL> cdelt = cdelt*3600.          ;Convert to arc sec/pixel
       IDL> dist_circle, circle, 512, x, y  ;Create a distance circle image
       IDL> circle = circle*abs(cdelt[0])   ;Distances now given in arcseconds
       IDL> good = where(circle LT 180)  ;Within 3 arc minutes
       IDL> print,total( IM[good] )      ;Total pixel values within 3'

 RESTRICTIONS:
       The speed of DIST_CIRCLE decreases and the the demands on virtual
       increase as the square of the output dimensions.   Users should
       dimension the output array as small as possible, and re-use the
       array rather than re-calling DIST_CIRCLE

 MODIFICATION HISTORY:
       Adapted from DIST    W. Landsman            March 1991
       Allow a rectangular output array   W. Landsman     June 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Add /DOUBLE keyword, make XCEN,YCEN optional  W. Landsman Jun 1998

(See $IDLUTILS_DIR/goddard/pro/image/dist_circle.pro)

DIST_ELLIPSE

 NAME:
       DIST_ELLIPSE
 PURPOSE:
       Create a mask array useful for elliptical aperture photemetry
 EXPLANATION:
       Form an array in which the value of each element is equal to the
       semi-major axis of the ellipse of specified center, axial ratio, and 
       position  angle, which passes through that element.  Useful for 
       elliptical aperture photometry.

 CALLING SEQUENCE:
       DIST_ELLIPSE, IM, N, XC, YC, RATIO, POS_ANG, /DOUBLE

 INPUTS:
       N = either  a scalar specifying the size of the N x N square output
               array, or a 2 element vector specifying the size of the
               M x N rectangular output array.
       XC,YC - Scalars giving the position of the ellipse center.   This does
               not necessarily have to be within the image
       RATIO - Scalar giving the ratio of the major to minor axis.   This 
               should be greater than 1 for postion angle to have its 
               standard meaning.

 OPTIONAL INPUTS:
       POS_ANG - Position angle of the major axis, measured counter-clockwise
               from the Y axis.  For an image in standard orientation 
               (North up, East left) this is the astronomical position angle.

 OPTIONAL INPUT KEYWORD:
       /DOUBLE - If this keyword is set and nonzero, the output array will
               be of type DOUBLE rather than floating point.

 OUTPUT:
       IM - REAL*4 elliptical mask array, of size M x N.  THe value of each 
               pixel is equal to the semi-major axis of the ellipse of center
                XC,YC, axial ratio RATIO, and position angle POS_ANG, which 
               passes through the pixel.

 EXAMPLE:
       Total the flux in a elliptical aperture with a major axis of 3', an
       axial ratio of 2.3, and a position angle of 25 degrees centered on 
       a specified RA and DEC.   The image array, IM is 200 x 200, and has 
       an associated FITS header H.

       ADXY, H, ra, dec, x, y       ;Get X and Y corresponding to RA and Dec
       GETROT, H, rot, cdelt        ;CDELT gives plate scale degrees/pixel
       cdelt = abs( cdelt)*3600.    ;CDELT now in arc seconds/pixel
       DIST_ELLIPSE, ell, 200, x, y, 2.3, 25  ;Create a elliptical image mask
       ell = ell*cdelt(0)           ;Distances now given in arcseconds
       good = where( ell lt 180 )   ;Within 3 arc minutes
       print,total( im(good) )      ;Total pixel values within 3'

 RESTRICTIONS:
       The speed of DIST_ELLIPSE decreases and the the demands on virtual
       increase as the square of the output dimensions.   Users should
       dimension the output array as small as possible, and re-use the
       array rather than re-calling DIST_ELLIPSE

 REVISION HISTORY:
       Written    W. Landsman             April, 1991
       Somewhat faster algorithm          August, 1992
       Allow rectangular output array     June, 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Added /DOUBLE keyword   W. Landsman   July 2000

(See $IDLUTILS_DIR/goddard/pro/image/dist_ellipse.pro)

ECI2GEO

 NAME:
     ECI2GEO

 PURPOSE:
     Convert Earth-centered inertial coordinates to geographic spherical coords
 EXPLANATION:
     Converts from ECI (Earth-Centered Inertial) (X,Y,Z) rectangular 
     coordinates to geographic spherical coordinates (latitude, longitude, 
     altitude).    JD time is also needed as input.

     ECI coordinates are in km from Earth center.
     Geographic coordinates are in degrees/degrees/km
     Geographic coordinates assume the Earth is a perfect sphere, with radius 
     equal to its equatorial radius.

 CALLING SEQUENCE:
     gcoord=eci2geo(ECI_XYZ,JDtime)

 INPUT:
       ECI_XYZ : the ECI [X,Y,Z] coordinates (in km), can be an array [3,n] 
                 of n such coordinates.
       JDtime: the Julian Day time, double precision. Can be a 1-D array of n 
                 such times.

 KEYWORD INPUTS:
       None

 OUTPUT:
       a 3-element array of geographic [latitude,longitude,altitude], or an 
         array [3,n] of n such coordinates, double precision  

 COMMON BLOCKS:
       None

 PROCEDURES USED:
       CT2LST - Convert Local Civil Time to Local Mean Sidereal Time

 EXAMPLE:
       IDL> gcoord=eci2geo([6378.137+600,0,0], 2452343.38982663D)
       IDL> print,gcoord
       0.0000000       232.27096       600.00000

       (The above is the geographic direction of the vernal point on 
       2002/03/09 21:21:21.021, in geographic coordinates. The chosen 
       altitude was 600 km.)

       gcoord can be further transformed into geodetic coordinates (using 
       geo2geodetic.pro) or into geomagnetic coordinates (using geo2mag.pro)

 MODIFICATION HISTORY:
       Written by Pascal Saint-Hilaire (Saint-Hilaire@astro.phys.ethz.ch) on 
              2001/05/13
       Modified on 2002/05/13, PSH : vectorization + use of JD times

(See $IDLUTILS_DIR/goddard/pro/astro/eci2geo.pro)

EQ2HOR

 NAME:
   EQ2HOR

 PURPOSE:
    Convert celestial  (ra-dec) coords to local horizon coords (alt-az).

 CALLING SEQUENCE:

    eq2hor, ra, dec, jd, alt, az, [ha, LAT= , LON= , /WS, OBSNAME= , $
                       /B1950 , PRECESS_= 0, NUTATE_= 0, REFRACT_= 0, $
                       ABERRATION_= 0, ALTITUDE= , /VERBOSE, _EXTRA= ]

 DESCRIPTION:
  This is a nice code to calculate horizon (alt,az) coordinates from equatorial
  (ra,dec) coords.   It is typically accurate to about 1 arcsecond or better (I
  have checked the output against the publicly available XEPHEM software). It
  performs precession, nutation, aberration, and refraction corrections.  The
  perhaps best thing about it is that it can take arrays as inputs, in all
  variables and keywords EXCEPT Lat, lon, and Altitude (the code assumes these
  aren't changing), and uses vector arithmetic in every calculation except
  when calculating the precession matrices.

 INPUT VARIABLES:
       RA   : Right Ascension of object  (J2000) in degrees (FK5); scalar or
              vector.
       Dec  : Declination of object (J2000) in degrees (FK5), scalar or vector.
       JD   : Julian Date [scalar or vector]

       Note: if RA and DEC are arrays, then alt and az will also be arrays.
             If RA and DEC are arrays, JD may be a scalar OR an array of the
             same dimensionality.

 OPTIONAL INPUT KEYWORDS:
       lat   : north geodetic latitude of location in degrees
       lon   : EAST longitude of location in degrees (Specify west longitude
               with a negative sign.)
       /WS    : Set this to get the azimuth measured westward from south (not
               East of North).
       obsname: Set this to a valid observatory name to be used by the
              astrolib OBSERVATORY procedure, which will return the latitude
              and longitude to be used by this program.
       /B1950 : Set this if your ra and dec are specified in B1950, FK4
              coordinates (instead of J2000, FK5)
       precess_ : Set this to 1 to force precession [default], 0 for no
               precession correction
       nutate_  : Set this to 1 to force nutation [default], 0 for no nutation.
       aberration_ : Set this to 1 to force aberration correction [default],
                     0 for no correction.
       refract_ : Set to 1 to force refraction correction [default], 0 for no
                     correction.
       altitude: The altitude of the observing location, in meters. [default=0].
       verbose: Set this for verbose output.  The default is verbose=0.
       _extra: This is for setting TEMPERATURE or PRESSURE explicitly, which are
               used by CO_REFRACT to calculate the refraction effect of the
               atmosphere. If you don't set these, the program will make an
               intelligent guess as to what they are (taking into account your
               altitude).  See CO_REFRACT for more details.

 OUTPUT VARIABLES: (all double precision)
       alt    : altitude (in degrees)
       az     : azimuth angle (in degrees, measured EAST from NORTH, but see
                keyword WS above.)
       ha     : hour angle (in degrees) (optional)

 DEPENDENCIES:
       NUTATE, PRECESS, OBSERVATORY, SUNPOS, ADSTRING() (from the astrolib)
       CO_NUTATE, CO_ABERRATION, CO_REFRACT, ALTAZ2HADEC

 BASIC STEPS
   Apply refraction correction to find apparent Alt.
   Calculate Local Mean Sidereal Time
   Calculate Local Apparent Sidereal Time
   Do Spherical Trig to find apparent hour angle, declination.
   Calculate Right Ascension from hour angle and local sidereal time.
   Nutation Correction to Ra-Dec
   Aberration correction to Ra-Dec
       Precess Ra-Dec to current equinox.


CORRECTIONS I DO NOT MAKE:
   *  Deflection of Light by the sun due to GR. (typically milliarcseconds,
        can be arseconds within one degree of the sun)
   *  The Effect of Annual Parallax (typically < 1 arcsecond)
   *  and more (see below)

 TO DO
    * Better Refraction Correction.  Need to put in wavelength dependence,
    and integrate through the atmosphere.
        * Topocentric Parallax Correction (will take into account elevation of
          the observatory)
    * Proper Motion (but this will require crazy lookup tables or something).
        * Difference between UTC and UT1 in determining LAST -- is this
          important?
        * Effect of Annual Parallax (is this the same as topocentric Parallax?)
    * Polar Motion
        * Better connection to Julian Date Calculator.

 EXAMPLE

  Find the position of the open cluster NGC 2264 at the Effelsburg Radio
  Telescope in Germany, on June 11, 2023, at local time 22:00 (METDST).
  The inputs will then be:

       Julian Date = 2460107.250
       Latitude = 50d 31m 36s
       Longitude = 06h 51m 18s
       Altitude = 369 meters
       RA (J2000) = 06h 40m 58.2s
       Dec(J2000) = 09d 53m 44.0s

  IDL> eq2hor, ten(6,40,58.2)*15., ten(9,53,44), 2460107.250d, alt, az, $
               lat=ten(50,31,36), lon=ten(6,51,18), altitude=369.0, /verb, $
                pres=980.0, temp=283.0

 The program produces this output (because the VERBOSE keyword was set)

 Latitude = +50 31 36.0   Longitude = +06 51 18.0
 Julian Date =  2460107.250000
 Ra, Dec:  06 40 58.2  +09 53 44.0   (J2000)
 Ra, Dec:  06 42 15.7  +09 52 19.2   (J2023.4422)
 Ra, Dec:  06 42 13.8  +09 52 26.9   (fully corrected)
 LMST = +11 46 42.0
 LAST = +11 46 41.4
 Hour Angle = +05 04 27.6  (hh:mm:ss)
 Az, El =  17 42 25.6  +16 25 10.3   (Apparent Coords)
 Az, El =  17 42 25.6  +16 28 22.8   (Observer Coords)

 Compare this with the result from XEPHEM:
 Az, El =  17h 42m 25.6s +16d 28m 21s

 This 1.8 arcsecond discrepancy in elevation arises primarily from slight
 differences in the way I calculate the refraction correction from XEPHEM, and
 is pretty typical.

 AUTHOR:
   Chris O'Dell
       Univ. of Wisconsin-Madison
   Observational Cosmology Laboratory
   Email: odell@cmb.physics.wisc.edu

(See $IDLUTILS_DIR/goddard/pro/astro/eq2hor.pro)

EQPOLE

 NAME:
       EQPOLE
 PURPOSE:
       Convert RA and Dec to X,Y using an equal-area polar projection.
 EXPLANATION:
       The output X and Y coordinates are scaled to be between
       -90 and +90 to go from equator to pole to equator. Output map points 
       can be centered on the north pole or south pole.

 CALLING SEQUENCE:
       EQPOLE, L, B, X, Y, [ /SOUTHPOLE ]

 INPUTS:
       L - longitude - scalar or vector, in degrees
       B - latitude - same number of elements as RA, in degrees

 OUTPUTS:
       X - X coordinate, same number of elements as RA.   X is normalized to
               be between -90 and 90.
       Y - Y coordinate, same number of elements as DEC.  Y is normalized to
               be between -90 and 90.

 KEYWORDS:

       /SOUTHPOLE      - Keyword to indicate that the plot is to be centered 
               on the south pole instead of the north pole.

 REVISION HISTORY:
       J. Bloch        LANL, SST-9     1.1     5/16/91
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/eqpole.pro)

EQPOLE_GRID

 NAME:
       EQPOLE_GRID

 PURPOSE:
       Produce an equal area polar projection grid overlay
 EXPLANATION:
       Grid is written on the current graphics device using the equal area 
       polar projection.   EQPOLE_GRID assumes that the output plot 
       coordinates span the x and y ranges of -90 to 90 for a region that 
       covers the equator to the chosen pole. The grid is assumed to go from 
       the equator to the chosen pole.

 CALLING SEQUENCE:

       EQPOLE_GRID[,DLONG,DLAT,[/SOUTHPOLE, LABEL = , /NEW, _EXTRA=]

 INPUTS:

       DLONG   = Optional input longitude line spacing in degrees. If left
                 out, defaults to 30.
       DLAT    = Optional input lattitude line spacing in degrees. If left
                 out, defaults to 30.

 INPUT KEYWORDS:

       /SOUTHPOLE       = Optional flag indicating that the output plot is
                         to be centered on the south rather than the north
                         pole.
       LABEL           = Optional flag for creating labels on the output
                         grid on the prime meridian and the equator for
                         lattitude and longitude lines. If set =2, then
                         the longitude lines are labeled in hours and minutes.
       CHARSIZE       = If /LABEL is set, then CHARSIZE specifies the size
                         of the label characters (passed to XYOUTS)
       CHARTHICK     =  If /LABEL is set, then CHARTHICK specifies the 
                         thickness of the label characters (passed to XYOUTS)
       /NEW          =   If this keyword is set, then EQPOLE_GRID will create
                         a new plot, rather than overlay an existing plot.

       Any valid keyword to OPLOT such as COLOR, LINESTYLE, THICK can be 
       passed to AITOFF_GRID (though the _EXTRA facility) to to specify the
       color, style, or thickness of the grid lines.
 OUTPUTS:
       Draws grid lines on current graphics device.

 EXAMPLE:
       Create a labeled equal area projection grid of the Galaxy, centered on
       the South pole, and overlay stars at specified Galactic longitudes, 
       glong and latitudes, glat

       IDL> eqpole_grid,/label,/new,/south       ;Create labeled grid
       IDL> eqpole, glong, glat, x,y      ;Convert to X,Y coordinates
       IDL> plots,x,y,psym=2              ;Overplot "star" positions.


 COPYRIGHT NOTICE:

       Copyright 1992, The Regents of the University of California. This
       software was produced under U.S. Government contract (W-7405-ENG-36)
       by Los Alamos National Laboratory, which is operated by the
       University of California for the U.S. Department of Energy.
       The U.S. Government is licensed to use, reproduce, and distribute
       this software. Neither the Government nor the University makes
       any warranty, express or implied, or assumes any liability or
       responsibility for the use of this software.

 AUTHOR AND MODIFICATIONS:

       J. Bloch        1.4     10/28/92
       Converted to IDL V5.0   W. Landsman   September 1997
       Create default plotting coords, if needed   W. Landsman  August 2000
       Added _EXTRA, CHARTHICK, CHARSIZE keywords  W. Landsman  March 2001

(See $IDLUTILS_DIR/goddard/pro/astro/eqpole_grid.pro)

ERROR_MESSAGE

 NAME:
    ERROR_MESSAGE

 PURPOSE:

    The purpose of this function  is to have a device-independent
    error messaging function. The error message is reported
    to the user by using DIALOG_MESSAGE if widgets are
    supported and MESSAGE otherwise.

    In general, the ERROR_MESSAGE function is not called directly.
    Rather, it is used in a CATCH error handler. Errors are thrown
    to ERROR_MESSAGE with the MESSAGE command. A typical CATCH error
    handler is shown below.

       Catch, theError
       IF theError NE 0 THEN BEGIN
          Catch, /Cancel
          void = Error_Message()
          RETURN
       ENDIF

    Error messages would get into the ERROR_MESSAGE function by
    throwing an error with the MESSAGE command, like this:

       IF test NE 1 THEN Message, 'The test failed.'

 AUTHOR:

   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:

    Utility.

 CALLING SEQUENCE:

    ok = Error_Message(the_Error_Message)

 INPUTS:

    the_Error_Message: This is a string argument containing the error
       message you want reported. If undefined, this variable is set
       to the string in the !Error_State.Msg system variable.

 KEYWORDS:

    ERROR: Set this keyword to cause Dialog_Message to use the ERROR
       reporting dialog. Note that a bug in IDL causes the ERROR dialog
       to be used whether this keyword is set to 0 or 1!

    INFORMATIONAL: Set this keyword to cause Dialog_Message to use the
       INFORMATION dialog instead of the WARNING dialog. Note that a bug
       in IDL causes the ERROR dialog to be used if this keyword is set to 0!
       
    NONAME: Normally, the name of the routine in which the error occurs is
       added to the error message. Setting this keyword will suppress this
       behavior.

    TITLE: Set this keyword to the title of the DIALOG_MESSAGE window. By
       default the keyword is set to 'System Error' unless !ERROR_STATE.NAME
       equals "IDL_M_USER_ERR", in which case it is set to "Trapped Error'.

    TRACEBACK: Setting this keyword results in an error traceback
       being printed to standard output with the PRINT command. Set to
       1 (ON) by default. Use TRACEBACK=0 to turn this functionality off.
       
    QUIET: Set this keyword to suppress the DIALOG_MESSAGE pop-up dialog.

 OUTPUTS:

    Currently the only output from the function is the string "OK".

 RESTRICTIONS:

    The WARNING Dialog_Message dialog is used by default.

 EXAMPLE:

    To handle an undefined variable error:

    IF N_Elements(variable) EQ 0 THEN $
       ok = Error_Message('Variable is undefined')

 MODIFICATION HISTORY:

    Written by: David W. Fanning, 27 April 1999.
    Added the calling routine's name in the message and NoName keyword. 31 Jan 2000. DWF.
    Added _Extra keyword. 10 February 2000. DWF.
    Forgot to add _Extra everywhere. Fixed for MAIN errors. 8 AUG 2000. DWF.
    Adding call routine's name to Traceback Report. 8 AUG 2000. DWF.
    Added ERROR, INFORMATIONAL, and TITLE keywords. 19 SEP 2002. DWF.
    Removed the requirement that you use the NONAME keyword with the MESSAGE
      command when generating user-trapped errors. 19 SEP 2002. DWF.
    Added distinctions between trapped errors (errors generated with the
      MESSAGE command) and IDL system errors. Note that if you call ERROR_MESSAGE
      directly, then the state of the !ERROR_STATE.NAME variable is set
      to the *last* error generated. It is better to access ERROR_MESSAGE
      indirectly in a Catch error handler from the MESSAGE command. 19 SEP 2002. DWF.
    Change on 19 SEP 2002 to eliminate NONAME requirement did not apply to object methods.
      Fixed program to also handle messages from object methods. 30 JULY 2003. DWF.
    Removed obsolete STR_SEP and replaced with STRSPLIT. 27 Oct 2004. DWF.
    Made a traceback the default case without setting TRACEBACK keyword. 19 Nov 2004. DWF.
    Added check for window connection specifically for CRON jobs. 6 May 2008. DWF.
    Added QUIET keyword. 18 October 2008. DWF.
    The traceback information was bypassed when in the PostScript device. Not what I
      had in mind. Fixed. 6 July 2009. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/error_message.pro)

EULER

 NAME:
     EULER
 PURPOSE:
     Transform between Galactic, celestial, and ecliptic coordinates.
 EXPLANATION:
     Use the procedure ASTRO to use this routine interactively

 CALLING SEQUENCE:
      EULER, AI, BI, AO, BO, [ SELECT, /FK4, /RADIAN, SELECT = ] 

 INPUTS:
       AI - Input Longitude, scalar or vector.  In DEGREES unless /RADIAN
            is set.  If only two parameters are supplied, then  AI and BI 
             will be modified to contain the output longitude and latitude.
       BI - Input Latitude in DEGREES

 OPTIONAL INPUT:
       SELECT - Integer (1-6) specifying type of coordinate transformation.  

      SELECT   From          To        |   SELECT      From            To
       1     RA-Dec (2000)  Galactic   |     4       Ecliptic      RA-Dec    
       2     Galactic       RA-DEC     |     5       Ecliptic      Galactic  
       3     RA-Dec         Ecliptic   |     6       Galactic      Ecliptic  

      If not supplied as a parameter or keyword, then EULER will prompt for 
      the value of SELECT
      Celestial coordinates (RA, Dec) should be given in equinox J2000 
      unless the /FK4 keyword is set.
 OUTPUTS:
       AO - Output Longitude in DEGREES, always double precision
       BO - Output Latitude in DEGREES, always double precision

 OPTIONAL INPUT KEYWORD:
       /FK4 - If this keyword is set and non-zero, then input and output 
             celestial and ecliptic coordinates should be given in equinox 
             B1950.
       /RADIAN - if set, then all input and output angles are in radians rather
             than degrees.
       SELECT  - The coordinate conversion integer (1-6) may alternatively be 
              specified as a keyword
 EXAMPLE:
       Find the Galactic coordinates of Cyg X-1 (ra=299.590315, dec=35.201604)
       IDL> ra = 299.590315d
       IDL> dec = 35.201604d
       IDL> euler,ra,dec,glong,glat,1 & print,glong,glat 
            71.334990, 3.0668335
 REVISION HISTORY:
       Written W. Landsman,  February 1987
       Adapted from Fortran by Daryl Yentis NRL
       Made J2000 the default, added /FK4 keyword  W. Landsman December 1998
       Add option to specify SELECT as a keyword W. Landsman March 2003
       Use less virtual memory for large input arrays W. Landsman June 2008
       Added /RADIAN input keyword  W. Landsman   Sep 2008

(See $IDLUTILS_DIR/goddard/pro/astro/euler.pro)

EXPAND_TILDE()

 NAME:
      EXPAND_TILDE()
               
 PURPOSE: 
       Expand tilde in UNIX directory names
               
 CALLING SEQUENCE: 
       IDL> output=expand_tilde(input)
    
 INPUTS: 
       INPUT = input file or directory name, scalar string

 OUTPUT:
       Returns expanded filename, scalar string
               
 EXAMPLES: 
       output=expand_tilde('~zarro/test.doc')
               ---> output='/usr/users/zarro'

 NOTES:
       This version of EXPAND_TILDE differs from the version in the Solar
       Library in that it does not call the functions EXIST and IDL_RELEASE.
       However, it should work identically.
 PROCEDURE CALLS:
       None.
 REVISION HISTORY: 
       Version 1,  17-Feb-1997,  D M Zarro.  Written
       Transfered from Solar Library   W. Landsman   Sep. 1997
       Made more robust  D. Zarro/W. Landsman  Sep. 2000
       Made even more robust (since things like ~zarro weren't being expanded)
       Zarro (EITI/GSFC, Mar 2001)

(See $IDLUTILS_DIR/goddard/pro/misc/expand_tilde.pro)

EXTAST

 NAME:
     EXTAST
 PURPOSE:
     Extract ASTrometry parameters from a FITS image header.
 EXPLANATION:
     Extract World Coordinate System information 
     ( http://fits.gsfc.nasa.gov/fits_wcs.html ) from a FITS header and 
     place it into an IDL structure.

 CALLING SEQUENCE:
     EXTAST, hdr, [ astr, noparams, ALT= ]   

 INPUT:
     HDR - variable containing the FITS header (string array)

 OUTPUTS:
     ASTR - Anonymous structure containing astrometry info from the FITS 
             header ASTR always contains the following tags (even though 
             some projections do not require all the parameters)
       .NAXIS - 2 element array giving image size
      .CD   -  2 x 2 array containing the astrometry parameters CD1_1 CD1_2
               in DEGREES/PIXEL                                 CD2_1 CD2_2
      .CDELT - 2 element double vector giving physical increment at the 
                 reference pixel
      .CRPIX - 2 element double vector giving X and Y coordinates of reference 
               pixel (def = NAXIS/2) in FITS convention (first pixel is 1,1)
      .CRVAL - 2 element double precision vector giving R.A. and DEC of 
             reference pixel in DEGREES
      .CTYPE - 2 element string vector giving projection types, default
             ['RA---TAN','DEC--TAN']
      .LONGPOLE - scalar giving native longitude of the celestial pole 
             (default = 180 for zenithal projections) 
      .LATPOLE - scalar giving native latitude of the celestial pole default=0)
      .PV2 - Vector of projection parameter associated with latitude axis
             PV2 will have up to 21 elements for the ZPN projection, up to 3 
             for the SIN projection and no more than 2 for any other 
             projection  
      .DISTORT - optional substructure specifying any distortion parameters
                 currently implemented only for "SIP" (Spitzer Imaging 
                 Polynomial) distortion parameters

       NOPARAMS -  Scalar indicating the results of EXTAST
             -1 = Failure - Header missing astrometry parameters
             1 = Success - Header contains CROTA + CDELT (AIPS-type) astrometry
             2 = Success - Header contains CDn_m astrometry, rec.    
             3 = Success - Header contains PCn_m + CDELT astrometry. 
             4 = Success - Header contains ST  Guide Star Survey astrometry
                           (see gsssextast.pro )
 OPTIONAL INPUT/OUTPUT KEYWORDS:
       ALT -  single character 'A' through 'Z' or ' ' specifying an alternate 
              astrometry system present in the FITS header.    The default is
              to use the primary astrometry or ALT = ' '.   If /ALT is set, 
              then this is equivalent to ALT = 'A'.   See Section 3.3 of 
              Greisen & Calabretta (2002, A&A, 395, 1061) for information about
              alternate astrometry keywords.    If not set on input, then
              ALT is set to ' ' on output.
 PROCEDURE:
       EXTAST checks for astrometry parameters in the following order:

       (1) the CD matrix PC1_1,PC1_2...plus CDELT*, CRPIX and CRVAL
       (2) the CD matrix CD1_1,CD1_2... plus CRPIX and CRVAL.   
       (3) CROTA2 (or CROTA1) and CDELT plus CRPIX and CRVAL.

       All three forms are valid FITS according to the paper "Representations 
       of World Coordinates in FITS by Greisen and Calabretta (2002, A&A, 395,
       1061 http://fits.gsfc.nasa.gov/fits_wcs.html ) although form (1) is 
       preferred.

 NOTES:
       1.  An anonymous structure is created to avoid structure definition
       conflicts.    This is needed because some projection systems
       require additional dimensions (i.e. spherical cube
       projections require a specification of the cube face).

       2,   Some FITS headers (e.g.from HST/ACS) include SIP forward distortion
       coefficients but do not include the reverse coefficients.   Currently,
       EXTAST only gives a warning that the reverse coefficients (RA,Dec to
       X,Y) are not present.   EXTAST should actually compute 
       the inverse coefficients, but this is not yet implemented..
 PROCEDURES CALLED:
      GSSSEXTAST, ZPARCHECK
 REVISION HISTORY
      Written by B. Boothman 4/15/86
      Accept CD001001 keywords               1-3-88
      Accept CD1_1, CD2_1... keywords    W. Landsman    Nov. 92
      Recognize GSSS FITS header         W. Landsman    June 94
      Get correct sign, when converting CDELT* to CD matrix for right-handed
      coordinate system                  W. Landsman   November 1998
      Consistent conversion between CROTA and CD matrix  October 2000
      CTYPE = 'PIXEL' means no astrometry params  W. Landsman January 2001
      Don't choke if only 1 CTYPE value given W. Landsman  August 2001
      Recognize PC00n00m keywords again (sigh...)  W. Landsman December 2001
      Recognize GSSS in ctype also       D. Finkbeiner Jan 2002
      Introduce ALT keyword              W. Landsman June 2003
      Fix error introduced June 2003 where free-format values would be
      truncated if more than 20 characters.  W. Landsman Aug 2003
      Further fix to free-format values -- slash need not be present Sep 2003
      Default value of LATPOLE is 90.0  W. Landsman February 2004
      Allow for distortion substructure, currently implemented only for
          SIP (Spitzer Imaging Polynomial)   W. Landsman February 2004 
      Correct LONGPOLE computation if CTYPE = ['*DEC','*RA'] W. L. Feb. 2004
      Assume since V5.3 (vector STRMID)  W. Landsman Feb 2004
      Yet another fix to free-format values   W. Landsman April 2004
      Introduce PV2 tag to replace PROJP1, PROJP2.. etc.  W. Landsman May 2004
      Convert NCP projection to generalized SIN   W. Landsman Aug 2004
      Add NAXIS tag to output structure  W. Landsman Jan 2007
      .CRPIX tag now Double instead of Float   W. Landsman  Apr 2007
      If duplicate keywords use the *last* value W. Landsman Aug 2008
      Fix typo for AZP projection, nonzero longpole N. Cunningham Feb 2009
      Give warning if reverse SIP coefficient not present  W. Landsman Nov 2011
      Allow obsolete CD matrix representations W. Landsman May 2012

(See $IDLUTILS_DIR/goddard/pro/astrom/extast.pro)

EXTGRP

 NAME:
	EXTGRP
 PURPOSE:
	Extract the group parameter information out of SXREAD output
 EXPLANATION:
	This procedure extracts the group parameter information out of a 
	header and parameter variable obtained from SXREAD.  This allows 
	astrometry, photometry and other parameters to be easily SXPARed by 
	conventional methods and allows the image and header to be saved in 
	a SIMPLE format.

 CALLING SEQUENCE:
	ExtGrp, hdr, par

 INPUT:
	HDR - The header which is to be converted (input and output)
	PAR - The Parameter string returned from a call to SXREAD

 OUTPUT:
	HDR -  The converted header, string array

 OTHER PROCEDURES CALLED:
	SXPAR(), SXADDPAR, SXGPAR(), STRN()

 HISTORY:
	25-JUN-90 Version 1 written
	13-JUL-92 Header finally added to this ancient procedure, code spiffed up
	a bit.  Now 3 times faster.  Added PTYPE comment inclusion.  E. Deutsch
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/extgrp.pro)

EXTRAP

 NAME:
       EXTRAP

 PURPOSE:
       This procedure fills in the ends of a one-dimensional array from
       interior portions using polynomial extrapolation.

 CATEGORY:
       Image processing

 CALLING SEQUENCE:
       EXTRAP, Deg, X, Y, Y2

 INPUT POSITIONAL PARAMETERS:
       Deg:   Degree of polynomial
       X:     Independent variable
       Y:     Dependent variable

 KEYWORD PARAMETERS:
       LIMS:  3-element array giving range of X to be used to fit
              polynomial and starting point where extrapolation is
              to be substituted; if not given, you click on a plot;
              order of elements is [xmin, xmax, xstart]; if LIMS is
              specified, then program is silent

 OUTPUT POSITIONAL PARAMETERS:
       Y2:    Dependent variable with extrapolated portion filled in

 SIDE EFFECTS:
     May pop a window for selecting range.

 MODIFICATION HISTORY:
     Written by RSH, RITSS, 14 Aug 98
     Spiffed up for library.  RSH, 6 Oct 98

(See $IDLUTILS_DIR/goddard/pro/image/skyadj_cube.pro)

FACTOR

 NAME:
       FACTOR
 PURPOSE:
       Find prime factors of a given number.
 CATEGORY:
 CALLING SEQUENCE:
       factor, x, p, n
 INPUTS:
       x = Number to factor (>1).       in
 KEYWORD PARAMETERS:
       Keywords:
         /QUIET  means do not print factors.
         /DEBUG  Means list steps as they happen.
         /TRY    Go beyond 20000 primes.
 OUTPUTS:
       p = Array of prime numbers.      out
       n = Count of each element of p.  out
 COMMON BLOCKS:
 NOTES:
       Note: see also prime, numfactors, print_fact.
 MODIFICATION HISTORY:
       R. Sterner.  4 Oct, 1988.
       RES 25 Oct, 1990 --- converted to IDL V2.
       R. Sterner, 1999 Jun 30 --- Improved (faster, bigger).
       R. Sterner, 1999 Jul  7 --- Bigger values (used unsigned).
       R. Sterner, 1999 Jul  9 --- Tried to make backward compatable.
       R. Sterner, 2000 Jan 06 --- Fixed to ignore non-positive numbers.
       Johns Hopkins University Applied Physics Laboratory.

 Copyright (C) 1988, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.

(See $IDLUTILS_DIR/goddard/pro/jhuapl/factor.pro)

FDECOMP

 NAME:
     FDECOMP
 PURPOSE:
     Routine to decompose file name(s) for any operating system.

 CALLING SEQUENCE:
     FDECOMP, filename, disk, dir, name, qual, [OSFamily = ]

 INPUT:
     filename - string file name(s), scalar or vector

 OUTPUTS:
     All the output parameters will have the same number of elements as 
       input filename 

       disk - disk name, always '' on a Unix machine, scalar or vector string
       dir - directory name, scalar or vector string
       name - file name, scalar or vector string 
       qual - qualifier, set equal to the characters beyond the last "."

 OPTIONAL INPUT KEYWORD:
     OSFamily -  scalar string specifying the operating system, must be either
             'Windows' or 'unix'.    If not supplied,
             then !VERSION.OS_FAMILY is used to determine the OS.
 EXAMPLES:
     Consider the following file names 

     unix:    file = '/itt/idl71/avg.pro' 
     Windows: file =  'd:\itt\idl71\avg.pro'
       
     then IDL> FDECOMP,  file, disk, dir, name, qual
       will return the following

                 Disk             Dir          Name        Qual    
       Unix:      ''            '/itt/idl71/'  'avg'       'pro'   
       Windows:    'd:'         \itt\idl71\    'avg'       'pro'   

 NOTES:
     (1) The period is removed between the name and qualifier 
     (2) Unlike the intrinsic FILE_BASENAME() and FILE_DIRNAME() functions,
         one can use FDECOMP to decompose a Windows file name on a Unix machine
         or a Unix filename on a Windows machine.

 ROUTINES CALLED:
     None.
 HISTORY
     version 1  D. Lindler  Oct 1986
     Include VMS DECNET machine name in disk    W. Landsman  HSTX  Feb. 94
     Converted to Mac IDL, I. Freedman HSTX March 1994          
     Major rewrite to accept vector filenames V5.3   W. Landsman June 2000
     Fix cases where disk name not always present  W. Landsman  Sep. 2000
     Make sure version defined for Windows  W. Landsman April 2004
     Include final delimiter in directory under Windows as advertised
                W. Landsman   May 2006
     Remove VMS support, W. Landsman    September 2006
     Remove MacOS branch (same as Unix) W. Landsman  August 2009

(See $IDLUTILS_DIR/goddard/pro/misc/fdecomp.pro)

FILTER_IMAGE

 NAME:
       FILTER_IMAGE

 PURPOSE:
       Identical to MEDIAN or SMOOTH but handle edges and allow iterations.
 EXPLANATION:
       Computes the average and/or median of pixels in moving box,
       replacing center pixel with the computed average and/or median,
       (using the IDL SMOOTH() or MEDIAN() functions).
       The main reason for using this function is the options to
       also process the pixels at edges and corners of image, and,
       to apply iterative smoothing simulating convolution with Gaussian,
       and/or to convolve image with a Gaussian kernel.    Users might also
       look at the function ESTIMATOR_FILTER() introduced in IDL 7.1.

 CALLING SEQUENCE:
       Result = filter_image( image, SMOOTH=width, MEDIAN = width, /ALL_PIXELS
                               /ITERATE, FWHM =,  /NO_FT_CONVOL)

 INPUT:
       image = 2-D array (matrix)

 OPTIONAL INPUT KEYWORDS:
       SMOOTH = scalar (odd) integer specifying the width of a square box 
               for moving average, in # pixels.  /SMOOTH  means use box 
               width = 3 pixels for smoothing.

        MEDIAN = scalar (usually odd) integer specifying the width of square 
               moving box for median filter, in # pixels.   /MEDIAN  means use
               box width = 3 pixels for median filter.
   
       /ALL_PIXELS causes the edges of image to be filtered as well.   This
               is accomplished by reflecting pixels adjacent to edges outward
               (similar to the /EDGE_WRAP keyword in CONVOL).
               Note that this is a different algorithm from the /EDGE_TRUNCATE 
               keyword to SMOOTH or CONVOL, which duplicates the nearest pixel.   

       /ITERATE means apply smooth(image,3) iteratively for a count of
               (box_width-1)/2 times (=radius), when box_width >= 5.
               This is equivalent to convolution with a Gaussian PSF
               of FWHM = 2 * sqrt( radius ) as radius gets large.
               Note that /ALL_PIXELS is automatically applied,
               giving better results in the iteration limit.
               (also, MEDIAN keyword is ignored when /ITER is specified).

       FWHM_GAUSSIAN = Full-width half-max of Gaussian to convolve with image. 
                       FWHM can be a single number (circular beam),
                       or 2 numbers giving axes of elliptical beam.

       /NO_FT_CONVOL causes the convolution to be computed directly,
               with intrinsic IDL CONVOL function.   The default is to use 
               FFT when factors of size are all LE 13.   Note that 
               external function convolve.pro handles both cases)

 OPTIONAL INPUT/OUTPUT KEYWORD:
     PSF = Array containing the PSF used during the convolution.   This 
           keyword is only active if the FWHM_GAUSSIAN keyword is also 
           specified.     If PSF is undefined on input, then upon output it
           contains the Gaussian convolution specified by the FWHM_GAUSSIAN
           keyword.    If the PSF array is defined on input then it is used 
           as the convolution kernel,  the value of the  FWHM_GAUSSIAN keyword
           is ignored.      Typically, on a first call set PSF to an undefined
           variable, which can be reused for subsequent calls to prevent 
           recalculation of the Gaussian PSF.
 RESULT:
       Function returns the smoothed, median filtered, or convolved image.
       If both SMOOTH and MEDIAN are specified, median filter is applied first.
       If only SMOOTH is applied, then output is of same type as input.  If
       either MEDIAN or FWHM_GAUSSIAN is supplied than the output is at least
       floating (double if the input image is double). 

 EXAMPLES:
       To apply 3x3 moving median filter and
       then 3x3 moving average, both applied to all pixels:

               Result = filter_image( image, /SMOOTH, /MEDIAN, /ALL )

       To iteratively apply 3x3 moving average filter for 4 = (9-1)/2 times,
       thus approximating convolution with Gaussian of FWHM = 2*sqrt(4) = 4 :

               Result = filter_image( image, SMOOTH=9, /ITER )

       To convolve all pixels with Gaussian of FWHM = 3.7 x 5.2 pixels:

               Result = filter_image( image, FWHM=[3.7,5.2], /ALL )

 EXTERNAL CALLS:
       function psf_gaussian
       function convolve
       pro factor
       function prime          ;all these called only if FWHM is specified

 PROCEDURE:
       If both /ALL_PIXELS (or /ITERATE)  keywords are set then
       create a larger image by reflecting the edges outward, then call the 
       IDL MEDIAN() or SMOOTH() function on the larger image, and just return 
       the central part (the original size image).

       NAN values are recognized during calls to MEDIAN() or SMOOTH(), but 
       not for convolution with a Gaussian (FWHM keyword supplied). 
 HISTORY:
       Written, 1991, Frank Varosi, NASA/GSFC.
       FV, 1992, added /ITERATE option.
       FV, 1993, added FWHM_GAUSSIAN= option.
       Use /EVEN call to median, recognize NAN values in SMOOTH 
                  W. Landsman   June 2001
       Added PSF keyword,   Bjorn Heijligers/WL, September 2001
       Keep same output data type if /ALL_PIXELS supplied A. Steffl Mar 2011

(See $IDLUTILS_DIR/goddard/pro/image/filter_image.pro)

FIND

 NAME:
	FIND
 PURPOSE:
	Find positive brightness perturbations (i.e stars) in an image 
 EXPLANATION:
	Also returns centroids and shape parameters (roundness & sharpness).
	Adapted from 1991 version of DAOPHOT, but does not allow for bad pixels
       and uses a slightly different centroid algorithm.

       Modified in March 2008 to use marginal Gaussian fits to find centroids       
 CALLING SEQUENCE:
	FIND, image, [ x, y, flux, sharp, round, hmin, fwhm, roundlim, sharplim 
		PRINT= , /SILENT, /MONITOR]

 INPUTS:
	image - 2 dimensional image array (integer or real) for which one
		wishes to identify the stars present

 OPTIONAL INPUTS:
	FIND will prompt for these parameters if not supplied

	hmin -  Threshold intensity for a point source - should generally 
		be 3 or 4 sigma above background RMS
	fwhm  - FWHM (in pixels) to be used in the convolve filter
	sharplim - 2 element vector giving low and high cutoff for the
		sharpness statistic (Default: [0.2,1.0] ).   Change this
		default only if the stars have significantly larger or 
		or smaller concentration than a Gaussian
	roundlim - 2 element vector giving low and high cutoff for the
		roundness statistic (Default: [-1.0,1.0] ).   Change this 
		default only if the stars are significantly elongated.

 OPTIONAL INPUT KEYWORDS:
       /MONITOR - Normally, FIND will display the results for each star 
                only if no output variables are supplied.   Set /MONITOR
                to always see the result of each individual star.
	/SILENT - set /SILENT keyword to suppress all output display 
	PRINT - if set and non-zero then FIND will also write its results to
		a file find.prt.   Also one can specify a different output file 
		name by setting PRINT = 'filename'.

 OPTIONAL OUTPUTS:
	x - vector containing x position of all stars identified by FIND
	y-  vector containing y position of all stars identified by FIND
	flux - vector containing flux of identified stars as determined
		by a Gaussian fit.  Fluxes are NOT converted to magnitudes.
	sharp - vector containing sharpness statistic for identified stars
	round - vector containing roundness statistic for identified stars

 NOTES:
	(1) The sharpness statistic compares the central pixel to the mean of 
       the surrounding pixels.   If this difference is greater than the 
       originally estimated height of the Gaussian or less than 0.2 the height of the
	Gaussian (for the default values of SHARPLIM) then the star will be
	rejected. 

       (2) More recent versions of FIND in DAOPHOT allow the possibility of
       ignoring bad pixels.    Unfortunately, to implement this in IDL
       would preclude the vectorization made possible with the CONVOL function
       and would run extremely slowly.

       (3) Modified in March 2008 to use marginal Gaussian distributions to 
       compute centroid.   (Formerly, find.pro determined centroids by locating
       where derivatives went to zero -- see cntrd.pro for this algorithm.   
       This was the method used in very old (~1984) versions of DAOPHOT. )   
       As discussed in more  detail in the comments to the code, the  centroid
       computation here is  the same as in IRAF DAOFIND but differs slightly 
       from the current DAOPHOT.
 PROCEDURE CALLS:
	GETOPT()
 REVISION HISTORY:
	Written W. Landsman, STX  February, 1987
	ROUND now an internal function in V3.1   W. Landsman July 1993
	Change variable name DERIV to DERIVAT    W. Landsman Feb. 1996
	Use /PRINT keyword instead of TEXTOUT    W. Landsman May  1996
	Changed loop indices to type LONG       W. Landsman Aug. 1997
       Replace DATATYPE() with size(/TNAME)   W. Landsman Nov. 2001
       Fix problem when PRINT= filename   W. Landsman   October 2002
       Fix problems with >32767 stars   D. Schlegel/W. Landsman Sep. 2004
       Fix error message when no stars found  S. Carey/W. Landsman Sep 2007
       Rewrite centroid computation to use marginal Gaussians W. Landsman 
                 Mar 2008
       Added Monitor keyword, /SILENT now suppresses all output 
                   W. Landsman    Nov 2008
       Work when threshold is negative (difference images) W. Landsman May 2010

(See $IDLUTILS_DIR/goddard/pro/idlphot/find.pro)

FINDPRO

 NAME:
     FINDPRO
 PURPOSE:
     Find all locations of a procedure in the IDL !PATH
 EXPLANATION:
     FINDPRO searces for the procedure name (as a .pro or a .sav file) in all 
     IDL libraries or directories given in the !PATH system variable.    This
     differs from the intrinsic FILE_WHICH() function which only finds the 
     first occurence of the procedure name.
               
 CALLING SEQUENCE:
    FINDPRO, [ Proc_Name, /NoPrint, DirList = , ProList = ]

 OPTIONAL INPUT:
     Proc_Name - Character string giving the name of the IDL procedure or 
             function. Do not include the ".pro" extension. If Proc_Name is
             omitted, the program will prompt for PROC_NAME.  "*" wildcards
             are permitted.

 OPTIONAL KEYWORD INPUT:
     /NoPrint - if set, then the file's path is not printed on the screen and
             absolutely no error messages are printed on the screen.  If not
             set, then - since the MESSAGE routine is used - error messages 
             will be printed but the printing of informational messages
             depends on the value of the !Quiet variable.

 OPTIONAL KEYWORD OUTPUTS:
     DirList - The directories in which the file is located are returned in
             the keyword as a string array.
             If the procedure is an intrinsic IDL procedure, then the 
             value of DirList = ['INTRINSIC'].
             If the procedure is not found, the value of DirList = [''].
     ProList - The list (full pathnames) of procedures found.  Useful if you
             are looking for the name of a procedure using wildcards.

     The order of the names in DirList and ProList is identical to the order
     in which the procedure name appears in the !PATH
 PROCEDURE:
     The system variable !PATH is parsed using EXPAND_PATH into individual 
     directories.  FILE_SEARCH() is used to search the directories for
     the procedure name.  If not found in !PATH, then the name is compared 
     with the list of intrinsic IDL procedures given by the ROUTINE_INFO()
     function. 

 EXAMPLE:
     (1) Find the procedure CURVEFIT.  Assume for this example that the user
     also has a copy of the curvefit.pro procedure in her home directory
     on a Unix machine.

       IDL> findpro, 'curvefit', DIRLIST=DirList
       Procedure curvefit.pro found in directory  /home/user/.
       Procedure curvefit.pro found in directory  /home/idl/lib/userlib 
       IDL> help, DirList
       DIRLIST         STRING    = Array(2) 
       IDL> help, DirList[0], DirList[1]
       <Expression>    STRING    = '/home/user'
       <Expression>    STRING    = '/home/idl/lib/userlib' 

     (2) Find all procedures in one's !path containing the characters "zoom" 

       IDL> findpro,'*zoom*'
 RESTRICTIONS:
       User will be unable to find a path for a native IDL function
       or procedure, or for a FORTRAN or C routine added with CALL_EXTERNAL.
       Remember that Unix is case sensitive, and most procedures will be in
       lower case.

 PROCEDURES USED:
       FDECOMP   -- Decompose file name
 REVISION HISTORY:
       Based on code extracted from the GETPRO procedure, J. Parker 1994
       Use the intrinsic EXPAND_PATH function    W. Landsman Nov. 1994
       Use ROUTINE_NAMES() to check for intrinsic procs   W. Landsman Jul 95
       Added Macintosh, WINDOWS compatibility    W. Landsman   Sep. 95
       Removed spurious first element in PROLIST  W. Landsman  March 1997
       Don't include duplicate directories  in !PATH  WL   May 1997
       Use ROUTINE_INFO instead of undocumented ROUTINE_NAMES W.L. October 1998
       Also check for save sets   W. Landsman  October 1999 
       Force lower case check for VMS  W. Landsman January 2000 
       Only return .pro or .sav files in PROLIST   W. Landsman  January 2002 
       Force lower case check for .pro and .sav    D. Swain  September 2002 
       Use FILE_SEARCH() if V5.5 or later   W. Landsman June 2006
       Assume since V55, remove VMS support W. Landsman Sep. 2006
       Assume since V6.0, use file_basename() W.Landsman Feb 2009

(See $IDLUTILS_DIR/goddard/pro/misc/findpro.pro)

FIND_ALL_DIR()

 NAME:
       FIND_ALL_DIR()
 PURPOSE:
       Finds all directories under a specified directory.
 EXPLANATION:
       This routine finds all the directories in a directory tree when the
       root of the tree is specified.  This provides the same functionality as
       having a directory with a plus in front of it in the environment
       variable IDL_PATH.

 CALLING SEQUENCE:
       Result = FIND_ALL_DIR( PATH )

               PATHS = FIND_ALL_DIR('+mypath', /PATH_FORMAT)
               PATHS = FIND_ALL_DIR('+mypath1:+mypath2')

 INPUTS:
       PATH    = The path specification for the top directory in the tree.
               Optionally this may begin with the '+' character but the action
               is the same unless the PLUS_REQUIRED keyword is set.

               One can also path a series of directories separated
               by the correct character ("," for VMS, ":" for Unix)

 OUTPUTS:
       The result of the function is a list of directories starting from the
       top directory passed and working downward from there.   Normally, this
       will be a string array with one directory per array element, but if
       the PATH_FORMAT keyword is set, then a single string will be returned,
       in the correct format to be incorporated into !PATH.

 OPTIONAL INPUT KEYWORDS:
       PATH_FORMAT     = If set, then a single string is returned, in
                                 the format of !PATH.

       PLUS_REQUIRED   = If set, then a leading plus sign is required
                       in order to expand out a directory tree.
                       This is especially useful if the input is a
                       series of directories, where some components
                       should be expanded, but others shouldn't.

       RESET   = Often FIND_ALL_DIR is used with logical names.  It
               can be rather slow to search through these subdirectories.
               The /RESET keyword can be used to redefine an environment
               variable so that subsequent calls don't need to look for the
               subdirectories.

               To use /RESET, the PATH parameter must contain the name of a
               *single* environment variable.  For example

                               setenv,'FITS_DATA=+/datadisk/fits'
                               dir = find_all_dir('FITS_DATA',/reset,/plus)

               The /RESET keyword is usually combined with /PLUS_REQUIRED.

 PROCEDURE CALLS:
       DEF_DIRLIST, FIND_WITH_DEF(), BREAK_PATH()

 RESTRICTIONS:
       PATH must point to a directory that actually exists.

 REVISION HISTORY:
               Version 11, Zarro (SM&A/GSFC), 23-March-00
                       Removed all calls to IS_DIR
               Version 12, William Thompson, GSFC, 02-Feb-2001
                       In Windows, use built-in expand_path if able.
               Version 13, William Thompson, GSFC, 23-Apr-2002
                       Follow logical links in Unix
                       (Suggested by Pascal Saint-Hilaire)
               Version 14, Zarro (EER/GSFC), 26-Oct-2002
                       Saved/restored current directory to protect against
                       often mysterious directory changes caused by 
                       spawning FIND in Unix
               Version 15, William Thompson, GSFC, 9-Feb-2004
                       Resolve environment variables in Windows.

 Version     : Version 16 W. Landsman GSFC Sep 2006
                        Remove VMS support

(See $IDLUTILS_DIR/goddard/pro/misc/find_all_dir.pro)

FIND_WITH_DEF()

 NAME: 
     FIND_WITH_DEF()    
 PURPOSE: 
     Searches for files with a default path and extension. 
 EXPLANATION:
     Finds files using default paths and extensions,   Using this routine
     together with environment variables allows an OS-independent approach
     to finding files.
 CALLING SEQUENCE: 
     Result = FIND_WITH_DEF( FILENAME, PATHS  [, EXTENSIONS ] )

 INPUTS: 
     FILENAME   = Name of file to be searched for.  It may either be a
                    complete filename, or the path or extension could be left
                    off, in which case the routine will attempt to find the
                    file using the default paths and extensions.

     PATHS      = One or more default paths to use in the search in case
                    FILENAME does not contain a path itself.  The individual
                    paths are separated by commas, although in UNIX, colons
                    can also be used.  In other words, PATHS has the same
                    format as !PATH, except that commas can be used as a
                    separator regardless of operating system.  The current
                    directory is always searched first, unless the keyword
                    NOCURRENT is set.

                    A leading $ can be used in any path to signal that what
                    follows is an environmental variable, but the $ is not
                    necessary.  Environmental variables can themselves contain
                    multiple paths.

 OPTIONAL INPUTS: 
     EXTENSIONS = Scalar string giving one or more extensions to append to 
                  end of filename if the filename does not contain one (e.g. 
                   ".dat").  The period is optional.  Multiple extensions can 
                   be separated by commas or colons.
 OUTPUTS: 
     The result of the function is the name of the file if successful, or
     the null string if unsuccessful.
 OPTIONAL INPUT KEYWORDS: 
     NOCURRENT = If set, then the current directory is not searched.

      RESET      = The FIND_WITH_DEF routine supports paths which are
                    preceeded with the plus sign to signal that all
                    subdirectories should also be searched.  Often this is
                    used with logical names.  It can be rather slow to search
                    through these subdirectories.  The /RESET keyword can be
                    used to redefine an environment variable so that
                    subsequent calls don't need to look for the
                    subdirectories.

                    To use /RESET, the PATHS parameter must contain the name
                    of a *single* environment variable.  For example

                     setenv,'FITS_DATA=+/datadisk/fits'
                     file = find_with_def('test.fits','FITS_DATA',/reset)

 EXAMPLE:

       FILENAME = ''
       READ, 'File to open: ', FILENAME
       FILE = FIND_WITH_DEF( FILENAME, 'SERTS_DATA', '.fix' )
       IF FILE NE '' THEN ...


 PROCEDURE CALLS: 
       BREAK_PATH(), FIND_ALL_DIR(), STR_SEP()
 REVISION HISTORY: 
       Version 1, William Thompson, GSFC, 3 May 1993.
               Removed trailing / and : characters.
               Fixed bugs
               Allow for commas within values of logical names.
               Added keyword NOCURRENT.
               Changed to call BREAK_PATH
       Version 2, William Thompson, GSFC, 3 November 1994
               Made EXTENSIONS optional.
       Version 3, William Thompson, GSFC, 30 April 1996
               Call FIND_ALL_DIR to resolve any plus signs.
       Version 4, S.V. Haugan, UiO, 5 June 1996
               Using OPENR,..,ERROR=ERROR to avoid an IDL 3.6
               internal nesting error.
       Version 5, R.A. Schwartz, GSFC, 11 July 1996
               Use SPEC_DIR to interpret PATH under VMS
       Version 6, William Thompson, GSFC, 5 August 1996
               Took out call to SPEC_DIR (i.e., reverted to version 4).  The
               use of SPEC_DIR was required to support logical names defined
               via SETLOG,/CONFINE.  However, it conflicted with the ability
               to use logical names with multiple values.  Removing the
               /CONFINE made it unnecessary to call SPEC_DIR in this routine.
       Version 7, William Thompson, GSFC, 6 August 1996
               Added keyword RESET
       Converted to IDL V5.0   W. Landsman   October 1997
       Use STRTRIM instead of TRIM,   W. Landsman   November 1998
       Use STRSPLIT instead of STR_SEP  W. Landsman  July 2002

(See $IDLUTILS_DIR/goddard/pro/misc/find_with_def.pro)

FITEXY

 NAME:
       FITEXY
 PURPOSE:
       Best straight-line fit to data with errors in both coordinates
 EXPLANATION:
       Linear Least-squares approximation in one-dimension (y = a + b*x),
               when both x and y data have errors

 CALLING EXAMPLE:
       FITEXY, x, y, A, B, X_SIG= , Y_SIG= , [sigma_A_B, chi_sq, q, TOL=]

 INPUTS:
       x = array of values for independent variable.
       y = array of data values assumed to be linearly dependent on x.

 REQUIRED INPUT KEYWORDS:
       X_SIGMA = scalar or array specifying the standard deviation of x data.
       Y_SIGMA = scalar or array specifying the standard deviation of y data.

 OPTIONAL INPUT KEYWORD:
       TOLERANCE = desired accuracy of minimum & zero location, default=1.e-3.

 OUTPUTS:
       A_intercept = constant parameter result of linear fit,
       B_slope = slope parameter, so that:
                       ( A_intercept + B_slope * x ) approximates the y data.
 OPTIONAL OUTPUT:
       sigma_A_B = two element array giving standard deviation of 
                A_intercept and B_slope parameters, respectively.
                The standard deviations are not meaningful if (i) the
                fit is poor (see parameter q), or (ii) b is so large that
                the data are consistent with a vertical (infinite b) line.
                If the data are consistent with *all* values of b, then
                sigma_A_B = [1e33,e33]  
       chi_sq = resulting minimum Chi-Square of Linear fit, scalar
       q - chi-sq probability, scalar (0-1) giving the probability that
              a correct model would give a value equal or larger than the
              observed chi squared.   A small value of q indicates a poor
              fit, perhaps because the errors are underestimated.   As 
              discussed by Tremaine et al. (2002, ApJ, 574, 740) an 
              underestimate of the errors (e.g. due to an intrinsic dispersion)
              can lead to a bias in the derived slope, and it may be worth
              enlarging the error bars to get a reduced chi_sq ~ 1

 COMMON:
       common fitexy, communicates the data for computation of chi-square.

 PROCEDURE CALLS:
       CHISQ_FITEXY()            ;Included in this file
       MINF_BRACKET, MINF_PARABOLIC, ZBRENT    ;In IDL Astronomy Library 
       MOMENT(), CHISQR_PDF()     ;In standard IDL distribution

 PROCEDURE:
       From "Numerical Recipes" column by Press and Teukolsky: 
       in "Computer in Physics",  May, 1992 Vol.6 No.3
       Also see the 2nd edition of the book "Numerical Recipes" by Press et al.

       In order to avoid  problems with data sets where X and Y are of very 
       different order of magnitude the data are normalized before the fitting
       process is started.     The following normalization is used:
       xx = (x - xm) / xs    and    sigx = x_sigma / xs    
                             where xm = MEAN(x) and xs = STDDEV(x)
       yy = (y - ym) / ys    and    sigy = y_sigma / ys    
                             where ym = MEAN(y) and ys = STDDEV(y)


 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC  September 1992.
       Now returns q rather than 1-q   W. Landsman  December 1992
       Use CHISQR_PDF, MOMENT instead of STDEV,CHI_SQR1 W. Landsman April 1998
       Fixed typo for initial guess of slope, this error was nearly
             always insignificant          W. Landsman   March 2000
       Normalize X,Y before calculation (from F. Holland) W. Landsman Nov 2006

(See $IDLUTILS_DIR/goddard/pro/math/fitexy.pro)

FITSDIR

 NAME:
     FITSDIR 
 PURPOSE:
     Display selected FITS keywords from the headers of FITS files.   
 EXPLANATION:

     The values of either user-specified or default FITS keywords are 
     displayed in either the primary header and/or the first extension header.
     Unless the /NOSIZE keyword is set, the data size is also displayed.
     The default keywords are as follows (with keywords in 2nd row used if
     those in the first row not found, and the 3rd row if neither the keywords
     in the first or second rows found:)

     DATE-OBS     TELESCOP   OBJECT    EXPTIME       
     TDATEOBS     TELNAME    TARGNAME  INTEG        ;First Alternative
     DATE         OBSERVAT             EXPOSURE     ;Second Alternative
                  INSTRUME             EXPTIM       ;Third Alternative

      FITSDIR will also recognize gzip compressed files (must have a .gz 
      or FTZ extension).
 CALLING SEQUENCE:
     FITSDIR , [ directory, TEXTOUT =, EXTEN=, KEYWORDS=, /NOSIZE, /NoTELESCOPE
                            ALT1_KEYWORDS= ,ALT2_KEYWORDS = ,ALT3_KEYWORDS =  

 OPTIONAL INPUT PARAMETERS:
     DIRECTORY - Scalar string giving file name, disk or directory to be 
             searched.   Wildcard file names are allowed.    Examples of 
             valid names include 'iraf/*.fits' (Unix), d:\myfiles\f*.fits',
             (Windows) or 'Macintosh HD:Files:*c0f.fits' (Macintosh).  
            
 OPTIONAL KEYWORD INPUT PARAMETER
      KEYWORDS - FITS keywords to display, as either a vector of strings or as
                 a comma delimited scalar string, e.g.'testname,dewar,filter'
                 If not supplied, then the default keywords are 'DATE-OBS',
                 'TELESCOP','OBJECT','EXPTIME'
      ALT1_KEYWORDS - A list (either a vector of strings or a comma delimited
                 strings of alternative keywords to use if the default 
                 KEYWORDS cannot be found.   By default, 'TDATEOBS', is the 
                 alternative to DATE-OBS, 'TELNAME' for 'TELESCOP','TARGNAME'
                 for 'OBJECT', and 'INTEG' for EXPTIME
      ALT2_KEYWORDS - A list (either a vector of strings or a comma delimited
                 strings of alternative keywords to use if neither KEYWORDS 
                 nor ALT1_KEYWORDS can be found.    
      ALT3_KEYWORDS - A list (either a vector of strings or a comma delimited
                 strings of alternative keywords to use if neither KEYWORDS 
                 nor ALT1_KEYWORDS nor ALT2_KEYWORDS can be found.    
      /NOSIZE - if set then information about the image size is not displayed  
      TEXTOUT - Controls output device as described in TEXTOPEN procedure
               textout=1       TERMINAL using /more option
               textout=2       TERMINAL without /more option
               textout=3       <program>.prt
               textout=4       laser.tmp
               textout=5       user must open file
               textout=7       Append to existing <program>.prt file
               textout = filename (default extension of .prt)
       EXTEN - Specifies an extension number (/EXTEN works for first extension)
               which is  checked for the  desired keywords.    
       /NOTELESCOPE - If set, then if the default keywords are used, then the
                TELESCOPE (or TELNAME, OBSERVAT, INSTRUME) keywords are omitted
                to give more room for display other keywords.   The /NOTELESCOP
                 keyword has no effect if the default keywords are not used.
 OUTPUT PARAMETERS:
       None.

 EXAMPLES:  
  (1) Print info on all'*.fits' files in the current  directory using default
          keywords.   Include information from the extension header     
       IDL> fitsdir,/exten

  (2) Write a driver program to display selected keywords in HST/ACS drizzled
       (*drz) images
         pro acsdir
        keywords = 'date-obs,targname,detector,filter1,filter2,exptime'
        fitsdir,'*drz.fits',key=keywords,/exten
        return & end

   (3)  Write info on all *.fits files in the Unix directory /usr2/smith, to a 
       file 'smith.txt' using the default keywords, but don't display the value
        of the TELESCOPE keyword

       IDL> fitsdir ,'/usr2/smith/*.fits',t='smith.txt', /NoTel 

 PROCEDURE:
       FILE_SEARCH()  is used to find the specified FITS files.   The 
       header of each file is read, and the selected keywords are extracted.
       The formatting is adjusted so that no value is truncated on display.        

 SYSTEM VARIABLES:
       TEXTOPEN (called by FITSDIR) will automatically define the following 
       non-standard system variables if they are not previously defined:

       DEFSYSV,'!TEXTOUT',1
       DEFSYSV,'!TEXTUNIT',0

 PROCEDURES USED:
       FDECOMP, FXMOVE, MRD_HREAD, REMCHAR
       TEXTOPEN, TEXTCLOSE
 MODIFICATION HISTORY:
       Written, W. Landsman,  HSTX    February, 1993
       Search alternate keyword names    W.Landsman    October 1998
       Avoid integer truncation for NAXISi >32767  W. Landsman  July 2000
       Don't leave open unit    W. Landsman  July 2000 
       Added EXTEN keyword, work with compressed files, additional alternate
       keywords W. Landsman     December 2000
       Don't assume floating pt. exposure time W. Landsman   September 2001
       Major rewrite, KEYWORD & ALT*_KEYWORDS keywords, no truncation, 
             /NOSIZE keyword     W. Landsman,  SSAI   August 2002
       Assume V5.3 or later W. Landsman November 2002
       Fix case where no keywords supplied  W. Landsman January 2003
       NAXIS* values must be integers W. Landsman SSAI  June 2003
       Trim spaces off of input KEYWORD values W. Landsman March 2004
       Treat .FTZ extension as gzip compressed  W. Landsman September 2004
       Assume since V5.5, file_search() available W. Landsman Aug 2006
       Don't assume all images compressed or uncompressed W. L. Apr 2010
       Use V6.0 notation W.L. Feb 2011

(See $IDLUTILS_DIR/goddard/pro/fits/fitsdir.pro)

FITSRGB_TO_TIFF

 NAME:
       FITSRGB_to_TIFF
 PURPOSE:
       Combine separate red, green, and blue FITS images into TIFF format
 EXPLANATION:
       The output TIFF (class R) file can have colors interleaved either
       by pixel or image.  The colour mix is also adjustable.

 CALLING SEQUENCE:
       FITSRGB_to_TIFF, path, rgb_files, tiff_name [,/BY_PIXEL, /PREVIEW,
                         RED= , GREEN =, BLUE =]

 INPUTS:
       path = file system directory path to the RGB files required.
       rgb_files = string array with three components - the red FITS file
                   filename, the blue FITS file filename and the green FITS
                   file filename

 OUTPUTS:
       tiff_name = string containing name of tiff file to be produced

 OPTIONAL OUTPUT:
       Header = String array containing the header from the FITS file.

 OPTIONAL INPUT KEYWORDS:
       BY_PIXEL = This causes TIFF file RGB to be interleaved by pixel
                  rather than the default of by image.
       PREVIEW  = Allows a 24 bit image to be displayed on the screen
                  to check the colour mix.
       RED = Real number containing the fractional mix of red
       GREEN = Real number containing the fractional mix of green
       BLUE = Real number containing the fractional mix of blue

 EXAMPLE:
       Read three FITS files, 'red.fits', 'blue.fits' and 'green.fits' from
       the directory '/data/images/space' and output a TIFF file named
       'colour.tiff'

               IDL> FITSRGB_to_TIFF, '/data/images/space', ['red.fits', $
                    'blue.fits', 'green.fits'], 'colour.tiff'

       Read three FITS files, 'red.fits', 'blue.fits' and 'green.fits' from
       the current directory and output a TIFF file named '/images/out.tiff'
       In this case, the red image is twice as strong as the green and the
       blue is a third more intense.  A preview on screen is also wanted.

               IDL> FITSRGB_to_TIFF, '.', ['red.fits', $
                    'blue.fits', 'green.fits'], '/images/out.tiff', $
                    /PREVIEW, RED=0.5, GREEN=1.0, BLUE=0.666


 RESTRICTIONS:
       (1) Limited to the ability of the routine READFITS

 NOTES:
       None

 PROCEDURES USED:
     Functions:   READFITS, CONCAT_DIR
     Procedures:  WRITE_TIFF

 MODIFICATION HISTORY:
     16th January 1995 - Written by Carl Shaw, Queen's University Belfast
	27 Jan 1995 - W. Landsman, Add CONCAT_DIR for VMS, Windows compatibility
	Converted to IDL V5.0   W. Landsman   September 1997
    Use WRITE_TIFF instead of obsolete TIFF_WRITE  W. Landsman  December 1998
    Cosmetic changes  W. Landsman    February 2000

(See $IDLUTILS_DIR/goddard/pro/fits/fitsrgb_to_tiff.pro)

FITS_ADD_CHECKSUM

 NAME:
    FITS_ADD_CHECKSUM
 PURPOSE:
    Add or update the CHECKSUM and DATASUM keywords in a FITS header
 EXPLANATION: 
     Follows the 23 May 2002 version of the FITS checksum proposal at 
     http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/checksum.html  
 CALLING SEQUENCE:
     FITS_ADD_CHECKSUM, Hdr, [ Data, /No_TIMESTAMP, /FROM_IEEE ]
 INPUT-OUTPUT:
     Hdr - FITS header (string array), it will be updated with new 
           (or modfied) CHECKSUM and DATASUM keywords 
 OPTIONAL INPUT:
     Data - data array associated with the FITS header.   If not supplied, or
           set to a scalar, then the program checks whether there is a 
           DATASUM keyword already in the FITS header containing the 32bit
           checksum for the data.   if there is no such keyword then there 
           assumed to be no data array associated with the FITS header.
 OPTIONAL INPUT KEYWORDS:
    /FROM_IEEE - If this keyword is set, then the input is assumed to be in 
             big endian format (e.g. an untranslated FITS array).    This 
             keyword only has an effect on little endian machines (e.g. 
             a Linux box).
    /No_TIMESTAMP - If set, then a time stamp is not included in the comment
             field of the CHECKSUM and DATASUM keywords.   Unless the 
             /No_TIMESTAMP keyword is set, repeated calls to FITS_ADD_CHECKSUM
             with the same header and data will yield different values of 
             CHECKSUM (as the date stamp always changes).   However, use of the
             date stamp is recommended in the checksum proposal. 
 PROCEDURES USED:
     CHECKSUM32, FITS_ASCII_ENCODE(), GET_DATE, SXADDPAR, SXPAR()
 REVISION HISTORY:
     W. Landsman    SSAI    December 2002
     Fix problem with images with a multiple of 2880 bytes.  W.L. May 2008
     Avoid conversion error when DATASUM is an empty string  W.L.  June 2008
     Don't update DATASUM if not already present and no data array supplied 
                       W.L. July 2008 
     Make sure input header array has 80 chars/line  W.L. Aug 2009

(See $IDLUTILS_DIR/goddard/pro/fits/fits_add_checksum.pro)

FITS_ASCII_ENCODE()

 NAME:
    FITS_ASCII_ENCODE()
 PURPOSE:
    Encode an unsigned longword as an ASCII string to insert in a FITS header
 EXPLANATION:
     Follows the 23 May 2002 version of the FITS checksum proposal at 
     http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/checksum.html   
 CALLING SEQUENCE:
     result = FITS_ASCII_ENCODE( sum32)
 INPUTS:
     sum32 - 32bit *unsigned longword* (e.g. as returned by CHECKSUM32)
 RESULT:
     A 16 character scalar string suitable for the CHECKSUM keyword
 EXAMPLE:
      A FITS header/data unit has a checksum of 868229149.  Encode the 
      complement of this value (3426738146) into an ASCII string

      IDL> print,FITS_ASCII_ENCODE(3426738146U)
           ===> "hcHjjc9ghcEghc9g"

 METHOD:
      The 32bit value is interpreted as a sequence of 4 unsigned 8 bit 
      integers, and divided by 4.    Add an offset of 48b (ASCII '0'). 
      Remove non-alphanumeric ASCII characters (byte values 58-64 and 91-96)
      by simultaneously incrementing and decrementing the values in pairs.
      Cyclicly shift the string one place to the right.
                  
 REVISION HISTORY:
     Written  W. Landsman  SSAI              December 2002

(See $IDLUTILS_DIR/goddard/pro/fits/fits_ascii_encode.pro)

FITS_CD_FIX

 NAME:
    FITS_CD_FIX

 PURPOSE:
    Update obsolete representations of the CD matrix in a FITS header   

 EXPLANATION:
    According the paper, "Representations of Celestial Coordinates in FITS"
    by Calabretta & Greisen (2002, A&A, 395, 1077, available at 
    http://fits.gsfc.nasa.gov/fits_wcs.html) the rotation of an image from 
    standard coordinates is represented by a coordinate description (CD) 
    matrix.    The standard representation of the CD matrix are PCn_m 
    keywords, but CDn_m keywords (which include the scale factors) are
    also allowed.    However, earliers drafts of the standard allowed the
    keywords forms CD00n00m and PC00n00m.      This procedure will convert
    FITS CD matrix keywords containing zeros into the standard forms 
    CDn_m and PCn_m containing only underscores.

 CALLING SEQUENCE:
    FITS_CD_FIX, Hdr

 INPUT-OUTPUT: 
       HDR - FITS header, 80 x N string array.   If the header does not
           contain 'CD00n00m' or 'PC00n00m' keywords then it is left 
           unmodified.  Otherwise, the keywords containing integers are
           replaced with those containing underscores.
   
 OPTIONAL KEYWORD INPUT
      /REVERSE - this keyword does nothing, but is kept for compatibility with
            earlier versions.
 PROCEDURES USED:
    SXADDPAR, SXDELPAR, SXPAR()
 REVISION HISTORY:
    Written   W. Landsman             Feb 1990
    Major rewrite                     Feb 1994
    Converted to IDL V5.0   W. Landsman   September 1997
    Use double precision formatting of CD matrix   W. Landsman  April 2000
    Major rewrite to convert only to forms recognized by the Greisen
       & Calabretta standard   W. Landsman   July 2003

(See $IDLUTILS_DIR/goddard/pro/astrom/fits_cd_fix.pro)

FITS_CLOSE

 NAME:
      FITS_CLOSE

*PURPOSE:
       Close a FITS data file

*CATEGORY:
       INPUT/OUTPUT

*CALLING SEQUENCE:
       FITS_CLOSE,fcb

*INPUTS:
       FCB: FITS control block returned by FITS_OPEN.

*KEYWORD PARAMETERS:
       /NO_ABORT: Set to return to calling program instead of a RETALL
               when an I/O error is encountered.  If set, the routine will
               return  a non-null string (containing the error message) in the
               keyword MESSAGE.   If /NO_ABORT not set, then FITS_CLOSE will 
               print the message and issue a RETALL
       MESSAGE = value: Output error message
       
*EXAMPLES:
       Open a FITS file, read some data, and close it with FITS_CLOSE

               FITS_OPEN,'infile',fcb
               FITS_READ,fcb,data
               FITS_READ,fcb,moredata
               FITS_CLOSE,fcb

*HISTORY:
       Written by:     D. Lindler      August, 1995
       Converted to IDL V5.0   W. Landsman   September 1997
       Do nothing if fcb an invalid structure D. Schlegel/W. Landsman Oct. 2000
       Return Message='' for to signal normal operation W. Landsman Nov. 2000

(See $IDLUTILS_DIR/goddard/pro/fits/fits_close.pro)

FITS_HELP

 NAME:
       FITS_HELP

 PURPOSE:
       To print a summary of the primary data units and extensions in a
       FITS file.
;
 CALLING SEQUENCE:
       FITS_HELP,filename_or_fcb

 INPUTS:
       FILENAME_OR_FCB - name of the fits file or the FITS Control Block (FCB)
               structure returned by FITS_OPEN.     The  file name is allowed 
               to be gzip compressed (with a .gz  extension)

 OUTPUTS:
       A summary of the FITS file is printed.   For each extension, the values
       of the XTENSION, EXTNAME EXTVER EXTLEVEL BITPIX GCOUNT, PCOUNT NAXIS 
       and NAXIS* keywords are displayed. 
 

 EXAMPLES:
       FITS_HELP,'myfile.fits'

       FITS_OPEN,'anotherfile.fits',fcb
       FITS_HELP,fcb

 PROCEDURES USED:
       FITS_OPEN, FITS_CLOSE
 HISTORY:
       Written by:     D. Lindler      August, 1995
       Converted to IDL V5.0   W. Landsman   September 1997
       Don't truncate EXTNAME values at 10 chars  W. Landsman Feb. 2005
       Use V6.0 notation W. Landsman Jan 2012

(See $IDLUTILS_DIR/goddard/pro/fits/fits_help.pro)

FITS_INFO

 NAME:
     FITS_INFO
 PURPOSE:
     Provide information about the contents of a FITS file
 EXPLANATION:
     Information includes number of header records and size of data array.
     Applies to primary header and all extensions.    Information can be 
     printed at the terminal and/or stored in a common block

     This routine is mostly obsolete, and better results can be usually be
     performed with FITS_HELP (for display) or FITS_OPEN (to read FITS 
     information into a structure)

 CALLING SEQUENCE:
     FITS_INFO, Filename, [ /SILENT , TEXTOUT = , N_ext =, EXTNAME= ]

 INPUT:
     Filename - Scalar string giving the name of the FITS file(s)
               Can include wildcards such as '*.fits', or regular expressions 
               allowed by the FILE_SEARCH() function.     One can also search 
               gzip compressed  FITS files, but their extension must
               end in .gz or .ftz.
 OPTIONAL INPUT KEYWORDS:
     /SILENT - If set, then the display of the file description on the 
                terminal will be suppressed

      TEXTOUT - specifies output device.
               textout=1        TERMINAL using /more option
               textout=2        TERMINAL without /more option
               textout=3        <program>.prt
               textout=4        laser.tmp
               textout=5        user must open file, see TEXTOPEN
               textout=7       append to existing <program.prt> file
               textout = filename (default extension of .prt)

               If TEXTOUT is not supplied, then !TEXTOUT is used
 OPTIONAL OUTPUT KEYWORDS:
       N_ext - Returns an integer scalar giving the number of extensions in
               the FITS file
       extname - returns a list containing the EXTNAME keywords for each
       		extension.

 COMMON BLOCKS
       DESCRIPTOR =  File descriptor string of the form N_hdrrec Naxis IDL_type
               Naxis1 Naxis2 ... Naxisn [N_hdrrec table_type Naxis
               IDL_type Naxis1 ... Naxisn] (repeated for each extension) 
               For example, the following descriptor 
                    167 2 4 3839 4 55 BINTABLE 2 1 89 5
 
               indicates that the  primary header containing 167 lines, and 
               the primary (2D) floating point image (IDL type 4) 
               is of size 3839 x 4.    The first extension header contains
               55 lines, and the  byte (IDL type 1) table array is of size
               89 x 5.

               The DESCRIPTOR is *only* computed if /SILENT is set.
 EXAMPLE:
       Display info about all FITS files of the form '*.fit' in the current
               directory

               IDL> fits_info, '*.fit'

       Any time a *.fit file is found which is *not* in FITS format, an error 
       message is displayed at the terminal and the program continues

 PROCEDURES USED:
       GETTOK(), MRD_SKIP, STRN(), SXPAR(), TEXTOPEN, TEXTCLOSE 

 SYSTEM VARIABLES:
       The non-standard system variables !TEXTOUT and !TEXTUNIT will be  
       created by FITS_INFO if they are not previously defined.   

       DEFSYSV,'!TEXTOUT',1
       DEFSYSV,'!TEXTUNIT',0

       See TEXTOPEN.PRO for more info
 MODIFICATION HISTORY:
       Written, K. Venkatakrishna, Hughes STX, May 1992
       Added N_ext keyword, and table_name info, G. Reichert
       Work on *very* large FITS files   October 92
       More checks to recognize corrupted FITS files     February, 1993
       Proper check for END keyword    December 1994
       Correctly size variable length binary tables  WBL December 1994
       EXTNAME keyword can be anywhere in extension header WBL  January 1998
       Correctly skip past extensions with no data   WBL   April 1998
       Converted to IDL V5.0, W. Landsman, April 1998
       No need for !TEXTOUT if /SILENT D.Finkbeiner   February 2002
       Define !TEXTOUT if needed.  R. Sterner, 2002 Aug 27
       Work on gzip compressed files for V5.3 or later  W. Landsman 2003 Jan
       Improve speed by only reading first 36 lines of header 
       Count headers with more than 32767 lines         W. Landsman Feb. 2003
       Assume since V5.3 (OPENR,/COMPRESS)   W. Landsman Feb 2004
       EXTNAME keyword can be anywhere in extension header again 
                         WBL/S. Bansal Dec 2004
       Read more than 200 extensions  WBL   March 2005
       Work for FITS files with SIMPLE=F   WBL July 2005
       Assume since V5.4, fstat.compress available WBL April 2006
       Added EXTNAME as an IDL keyword to return values. M. Perrin Dec 2007
       make Ndata a long64 to deal with large files. E. Hivon Mar 2008
       For GDL compatibility, first check if file is compressed  before using
          OPENR,/COMPRESS  B. Roukema/WL    Apr 2010

(See $IDLUTILS_DIR/goddard/pro/fits/fits_info.pro)

FITS_OPEN

 NAME:
       FITS_OPEN

 PURPOSE:
       Opens a FITS (Flexible Image Transport System) data file.

 EXPLANATION:
       Used by FITS_READ and FITS_WRITE

 CALLING SEQUENCE:
       FITS_OPEN, filename, fcb

 INPUTS:
       filename : name of the FITS file to open, scalar string
                  FITS_OPEN can also open gzip compressed (.gz) file *for 
                  reading only*, although there is a performance penalty 
                  FPACK ( http://heasarc.gsfc.nasa.gov/fitsio/fpack/ ) 
                  compressed FITS files can be read provided that the FPACK 
                  software is installed.
*OUTPUTS:
       fcb : (FITS Control Block) a IDL structure containing information
               concerning the file.  It is an input to FITS_READ, FITS_WRITE
               FITS_CLOSE and MODFITS.  
 INPUT KEYWORD PARAMETERS:
       /APPEND: Set to append to an existing file.
       /FPACK - Signal that the file is compressed with the FPACK software. 
               http://heasarc.gsfc.nasa.gov/fitsio/fpack/ ) By default, 
               FITS_OPEN assumes that if the file name extension ends in 
               .fz that it is fpack compressed.     The FPACK software must
               be installed on the system 
       /HPRINT - print headers with routine HPRINT as they are read.
               (useful for debugging a strange file)
       /NO_ABORT: Set to quietly return to calling program when an I/O error  
               is encountered, and return  a non-null string
               (containing the error message) in the keyword MESSAGE.    
               If /NO_ABORT not set, then FITS_OPEN will display the error 
               message and return to the calling program.
       /UPDATE Set this keyword to open an existing file for update
       /WRITE: Set this keyword to open a new file for writing. 

 OUTPUT KEYWORD PARAMETERS:
       MESSAGE = value: Output error message.    If the FITS file was opened
               successfully, then message = ''.
       
 NOTES:
       The output FCB should be passed to the other FITS routines (FITS_OPEN,
       FITS_READ, FITS_HELP, and FITS_WRITE).  It has the following structure
       when FITS_OPEN is called without /WRITE or /APPEND keywords set.

           FCB.FILENAME - name of the input file
               .UNIT - unit number the file is opened to
               .FCOMPRESS - 1 if unit is a FPACK compressed file opened with
                    a pipe to SPAWN
               .NEXTEND - number of extensions in the file.
               .XTENSION - string array giving the extension type for each
                       extension.
               .EXTNAME - string array giving the extension name for each
                       extension. (null string if not defined the extension)
               .EXTVER - vector of extension version numbers (0 if not
                       defined)
               .EXTLEVEL - vector of extension levels (0 if not defined)
               .GCOUNT - vector with the number of groups in each extension.
               .PCOUNT - vector with parameter count for each group
               .BITPIX - BITPIX for each extension with values
                                  8    byte data
                                16     short word integers
                                32     long word integers
                               -32     IEEE floating point
                               -64     IEEE double precision floating point
               .NAXIS - number of axes for each extension.  (0 for null data
                       units)
               .AXIS - 2-D array where axis(*,N) gives the size of each axes
                       for extension N
               .START_HEADER - vector giving the starting byte in the file
                               where each extension header begins
               .START_DATA - vector giving the starting byte in the file
                               where the data for each extension begins

               .HMAIN - keyword parameters (less standard required FITS
                               keywords) for the primary data unit.
               .OPEN_FOR_WRITE - flag (0= open for read, 1=open for write, 
                                                2=open for update)
               .LAST_EXTENSION - last extension number read.
               .RANDOM_GROUPS - 1 if the PDU is random groups format,
                               0 otherwise
               .NBYTES - total number of (uncompressed) bytes in the FITS file

       When FITS open is called with the /WRITE or /APPEND option, FCB
       contains:

           FCB.FILENAME - name of the input file
               .UNIT - unit number the file is opened to
               .NEXTEND - number of extensions in the file.
               .OPEN_FOR_WRITE - flag (1=open for write, 2=open for append
                                       3=open for update)


 EXAMPLES:
       Open a FITS file for reading:
               FITS_OPEN,'myfile.fits',fcb

       Open a new FITS file for output:
               FITS_OPEN,'newfile.fits',fcb,/write
 PROCEDURES USED:
       GET_PIPE_FILESIZE (for Fcompress'ed files) HPRINT, SXDELPAR, SXPAR()
 HISTORY:
       Written by:     D. Lindler      August, 1995
       July, 1996      NICMOS  Modified to allow open for overwrite
                               to allow primary header to be modified
       DJL Oct. 15, 1996   corrected to properly extend AXIS when more
                       than 100 extensions present
       Converted to IDL V5.0   W. Landsman   September 1997
       Use Message = '' rather than !ERR =1 as preferred signal of normal
           operation   W. Landsman  November 2000
       Lindler, Dec, 2001, Modified to use 64 bit words for storing byte
             positions within the file to allow support for very large
             files 
       Work with gzip compressed files W. Landsman    January 2003
       Fix gzip compress for V5.4 and earlier  W.Landsman/M.Fitzgerald Dec 2003 
       Assume since V5.3 (STRSPLIT, OPENR,/COMPRESS) W. Landsman Feb 2004
       Treat FTZ extension as gzip compressed W. Landsman Sep 2004
       Assume since V5.4 fstat.compress available W. Landsman Apr 2006
       FCB.Filename  now expands any wildcards W. Landsman July 2006
       Make ndata 64bit for very large files B. Garwood/W. Landsman Sep 2006
       Open with /SWAP_IF_LITTLE_ENDIAN, remove obsolete keywords to OPEN
                W. Landsman  Sep 2006
       Warn that one cannot open a compressed file for update W.L. April 2007
       Use post-V6.0 notation W.L. October 2010
       Support FPACK compressed files, new .FCOMPRESS tag to FCB structure
               W.L.  December 2010

(See $IDLUTILS_DIR/goddard/pro/fits/fits_open.pro)

FITS_READ

 NAME:
       FITS_READ
 PURPOSE:
       To read a FITS file.

 CALLING SEQUENCE:
       FITS_READ, filename_or_fcb, data [,header, group_par]

 INPUTS:
       FILENAME_OR_FCB - this parameter can be the FITS Control Block (FCB)
               returned by FITS_OPEN or the file name of the FITS file.  If
               a file name is supplied, FITS_READ will open the file with
               FITS_OPEN and close the file with FITS_CLOSE before exiting.
               When multiple extensions are to be read from the file, it is
               more efficient for the user to call FITS_OPEN and leave the
               file open until all extensions are read. FPACK 
               ( http://heasarc.gsfc.nasa.gov/fitsio/fpack/ ) compressed FITS 
               files can be read provided that the FPACK software is installed.  

 OUTPUTS:
       DATA - data array.  If /NOSCALE is specified, BSCALE and BZERO
               (if present in the header) will not be used to scale the data.
               If Keywords FIRST and LAST are used to read a portion of the
               data or the heap portion of an extension, no scaling is done
               and data is returned as a 1-D vector. The user can use the IDL
               function REFORM to convert the data to the correct dimensions
               if desired.  If /DATA_ONLY is specified, no scaling is done.
       HEADER - FITS Header.  The STScI inheritance convention is recognized
               http://fits.gsfc.nasa.gov/registry/inherit/fits_inheritance.txt
               If an extension is read, and the INHERIT keyword exists with a 
               value of T, and the /NO_PDU keyword keyword is not supplied, 
               then the primary data unit header and the extension header will
                be combined.  The header will have the form:

                       <required keywords for the extension: XTENSION, BITPIX,
                               NAXIS, ...>
                       BEGIN MAIN HEADER --------------------------------
                       <PDU header keyword and history less required keywords:
                               SIMPLE, BITPIX, NAXIS, ...>
                       BEGIN EXTENSION HEADER ---------------------------
                       <extension header less required keywords that were
                               placed at the beginning of the header.
                       END
               
               The structure of the header is such that if a keyword is
               duplicated in both the PDU and extension headers, routine
               SXPAR will print a warning and return the extension value of
               the keyword. 

       GROUP_PAR - Group parameter block for FITS random groups format files
               or the heap area for variable length binary tables.
               Any scale factors in the header (PSCALn and PZEROn) are not
               applied to the group parameters.

 INPUT KEYWORD PARAMETERS:

       /NOSCALE: Set to return the FITS data without applying the scale
               factors BZERO and BSCALE.
       /HEADER_ONLY: set to read the header only.
       /DATA_ONLY: set to read the data only.  If set, if any scale factors
               are present (BSCALE or BZERO), they will not be applied.
       /NO_PDU: By default, FITS_READ will add the primary data unit header 
               keywords to the output header, *if* the header includes 
               INHERIT = T.   Set /NO_PDU to never append the primary header.
       /NO_ABORT: Set to return to calling program instead of a RETALL
               when an I/O error is encountered.  If set, the routine will
               return  a non-null string (containing the error message) in the
               keyword MESSAGE.    (For backward compatibility, the obsolete 
               system variable !ERR is also set to -1 in case of an error.)   
               If /NO_ABORT not set, then FITS_READ will print the message and
               issue a RETALL
       /NO_UNSIGNED - By default, if  the header indicates an unsigned integer
              (BITPIX = 16, BZERO=2^15, BSCALE=1) then FITS_READ will output 
               an IDL unsigned integer data type (UINT).   But if /NO_UNSIGNED
               is set, then the data is converted to type LONG.  
       /PDU - If set, then always add the primary data unit header keywords
              to the output header, even if the INHERIT=T keyword is not found
              This was the default behavior of FITS_READ prior to April 2007
       EXTEN_NO - extension number to read.  If not set, the next extension
               in the file is read.  Set to 0 to read the primary data unit.
       XTENSION - string name of the xtension to read
       EXTNAME - string name of the extname to read
       EXTVER - integer version number to read
       EXTLEVEL - integer extension level to read
       FIRST - set this keyword to only read a portion of the data.  It gives
               the first word of the data to read
       LAST - set this keyword to only read a portion of the data.  It gives
               the last word number of the data to read
       GROUP - group number to read for GCOUNT>1.  (Default=0, the first group)
       
 OUTPUT KEYWORD PARAMETERS:
       ENUM - Output extension number that was read.  
       MESSAGE = value: Output error message

 NOTES:
       Determination or which extension to read.
               case 1: EXTEN_NO specified. EXTEN_NO will give the number of the
                       extension to read.  The primary data unit is refered
                       to as extension 0. If EXTEN_NO is specified, XTENSION,
                       EXTNAME, EXTVER, and EXTLEVEL parameters are ignored.
               case 2: if EXTEN_NO is not specified, the first extension
                       with the specified XTENSION, EXTNAME, EXTVER, and
                       EXTLEVEL will be read.  If any of the 4 parameters
                       are not specified, they will not be used in the search.
                       Setting EXTLEVEL=0, EXTVER=0, EXTNAME='', or
                       XTENSION='' is the same as not supplying them.
               case 3: if none of the keyword parameters, EXTEN_NO, XTENSION,
                       EXTNAME, EXTVER, or EXTLEVEL are supplied.  FITS_READ
                       will read the next extension in the file.  If the
                       primary data unit (PDU), extension 0, is null, the
                       first call to FITS_READ will read the first extension
                       of the file.

               The only way to read a null PDU is to use EXTEN_NO = 0.

       If FIRST and LAST are specified, the data is returned without applying
       any scale factors (BSCALE and BZERO) and the data is returned in a
       1-D vector.  This will allow you to read any portion of a multiple
       dimension data set.  Once returned, the IDL function REFORM can be
       used to place the correct dimensions on the data.

       IMPLICIT IMAGES: FITS_READ will construct an implicit image
               for cases where NAXIS=0 and the NPIX1, NPIX2, and PIXVALUE
               keywords are present.  The output image will be:
                       image = replicate(PIXVALUE,NPIX1,NPIX2)

      FPACK compressed files are always closed and reopened when exiting 
      FITS_READ so that the pointer is set to the beginning of the file. (Since 
      FPACK files are opened with a bidirectional pipe rather than OPEN, one 
      cannot use POINT_LUN to move to a specified position in the file.)

 EXAMPLES:
       Read the primary data unit of a FITS file, if it is null read the
       first extension:
               FITS_READ, 'myfile.fits', data, header

       Read the first two extensions of a FITS file and the extension with
       EXTNAME = 'FLUX' and EXTVER = 4
               FITS_OPEN, 'myfile.fits', fcb
               FITS_READ, fcb,data1, header2, exten_no = 1
               FITS_READ, fcb,data1, header2, exten_no = 2
               FITS_READ, fcb,data3, header3, extname='flux', extver=4
               FITS_CLOSE, fcb
       
       Read the sixth image in a data cube for the fourth extension.

               FITS_OPEN, 'myfile.fits', fcb
               image_number = 6
               ns = fcb.axis(0,4)
               nl = fcb.axis(1,4)
               i1 = (ns*nl)*(image_number-1)
               i2 = i2 + ns*nl-1
               FITS_READ,fcb,image,header,first=i1,last=i2
               image = reform(image,ns,nl,/overwrite)
               FITS_CLOSE

 PROCEDURES USED:
       FITS_CLOSE, FITS_OPEN
       SXADDPAR, SXDELPAR, SXPAR()
 WARNINGS:
       In Sep 2006, FITS_OPEN was modified to open FITS files using the
       /SWAP_IF_LITTLE_ENDIAN keyword to OPEN, so that subsequent routines 
       (FITS_READ, FITS_WRITE) did not require any byte swapping.    An error
       may result if an pre-Sep 2006 version of FITS_OPEN is used with a 
       post Sep 2006 version of FITS_READ, FITS_WRITE or MODFITS.
 HISTORY:
       Written by:     D. Lindler, August 1995
       Avoid use of !ERR       W. Landsman   August 1999
       Read unsigned datatypes, added /no_unsigned   W. Landsman December 1999
       Don't call FITS_CLOSE unless fcb is defined   W. Landsman January 2000
       Set BZERO = 0 for unsigned integer data   W. Landsman  January 2000
       Only call IEEE_TO_HOST if needed          W. Landsman February 2000
       Ensure EXTEND keyword in primary header   W. Landsman April 2001
       Don't erase ERROR message when closing file  W. Landsman April 2002
       Assume at least V5.1 remove NANValue keyword  W. Landsman November 2002
       Work with compress files (read file size from fcb),
       requires updated (Jan 2003) version of FITS_OPEN W. Landsman Jan 2003
       Do not modify BSCALE/BZERO for  unsigned integers W. Landsman April 2006
       Asuume FITS_OPEN has opened the file with /SWAP_IF_LITTLE_ENDIAN
                         W. Landsman   September 2006
       Fix problem with /DATA_ONLY keyword  M.Buie/W.Landsman  October 2006
       Only append primary header if INHERIT=T  W. Landsman  April 2007
       Make ndata 64bit for very large files E. Hivon/W. Landsman May 2007
       Added /PDU keyword to always append primary header W. Landsman June 2007
       Use PRODUCT to compute # of data points   W. Landsman  May 2009
       Make sure FIRST is long64 when computing position W.L. October 2009
       Read FPACK compressed files, W.L.  December 2010

(See $IDLUTILS_DIR/goddard/pro/fits/fits_read.pro)

FITS_TEST_CHECKSUM()

 NAME:
    FITS_TEST_CHECKSUM()
 PURPOSE:
    Verify the values of the CHECKSUM and DATASUM keywords in a FITS header 
 EXPLANATION: 
     Follows the 2007 version of the FITS checksum proposal at 
     http://fits.gsfc.nasa.gov/registry/checksum.html
 
 CALLING SEQUENCE:
    result = FITS_TEST_CHECKSUM(HDR, [ DATA, ERRMSG=, /FROM_IEEE ])
 INPUTS:
    HDR - FITS header (vector string)
 OPTIONAL DATA:
    DATA - data array associated with the FITS header.   If not supplied, or
           set to a scalar, then there is assumed to be no data array 
           associated with the FITS header.
 RESULT:
     An integer -1, 0 or 1 indicating the following conditions:
           1 - CHECKSUM (and DATASUM) keywords are present with correct values
           0 - CHECKSUM keyword is not present
          -1 - CHECKSUM or DATASUM keyword does not have the correct value
               indicating possible data corruption.
 OPTIONAL INPUT KEYWORD:
    /FROM_IEEE - If this keyword is set, then the input is assumed to be in 
             big endian format (e.g. an untranslated FITS array).    This 
             keyword only has an effect on little endian machines (e.g. 
             a Linux box).
 OPTIONAL OUTPUT KEYWORD:
     ERRMSG - will contain a scalar string giving the error condition.   If
              RESULT = 1 then ERRMSG will be an empty string.   If this 
              output keyword is not supplied, then the error message will be
              printed at the terminal.
 NOTES:
     The header and data must be *exactly* as originally written in the FITS 
     file.  By default, some FITS readers may alter keyword values (e.g. 
     BSCALE) or append information (e.g. HISTORY or an inherited primary 
     header) and this will alter the checksum value.           
 PROCEDURES USED:
    CHECKSUM32, FITS_ASCII_ENCODE(), SXPAR()
 EXAMPLE:
     Verify the CHECKSUM keywords in the primary header/data unit of a FITS 
     file 'test.fits'

     FITS_READ,'test.fits',data,hdr,/no_PDU,/NoSCALE
     print,FITS_TEST_CHECKSUM(hdr,data)

     Note the use of the /No_PDU and /NoSCALE keywords to avoid any alteration 
     of the FITS header
 REVISION HISTORY:
     W. Landsman  SSAI               December 2002
     Return quietly if CHECKSUM keywords not found W. Landsman May 2003
     Add /NOSAVE to CHECKSUM32 calls when possible W. Landsman Sep 2004

(See $IDLUTILS_DIR/goddard/pro/fits/fits_test_checksum.pro)

FITS_WRITE

 NAME:
	FITS_WRITE

 PURPOSE:
	To write a FITS primary data unit or extension.

 EXPLANATION:
       ***NOTE** This version of FITS_READ must be used with a post Sep 2006
          version of FITS_OPEN.

 CALLING SEQUENCE:
	FITS_WRITE, filename_or_fcb, data, [header_in]

 INPUTS:
	FILENAME_OR_FCB: name of the output data file or the FITS control
		block returned by FITS_OPEN (called with the /WRITE or
		/APPEND) parameters.

 OPTIONAL INPUTS:
	DATA: data array to write.  If not supplied or set to a scalar, a
		null image is written.
	HEADER_IN: FITS header keyword.  If not supplied, a minimal basic
		header will be created.  Required FITS keywords, SIMPLE,
		BITPIX, XTENSION, NAXIS, ... are added by FITS_WRITE and
		do not need to be supplied with the header.  If supplied,
		their values will be updated as necessary to reflect DATA.

 INPUT KEYWORD PARAMETERS:

	XTENSION: type of extension to write (Default="IMAGE"). If not
		supplied, it will be taken from HEADER_IN.  If not in either
		place, the default is "IMAGE".  This parameter is ignored
		when writing the primary data unit.     Note that binary and
               and ASCII table extensions already have a properly formatted
               header (e.g. with TTYPE* keywords) and byte array data. 
	EXTNAME: EXTNAME for the extension.  If not supplied, it will be taken
		from HEADER_IN.  If not supplied and not in HEADER_IN, no
		EXTNAME will be written into the output extension.
	EXTVER: EXTVER for the extension.  If not supplied, it will be taken
               from HEADER_IN.  If not supplied and not in HEADER_IN, no
               EXTVER will be written into the output extension.
	EXTLEVEL: EXTLEVEL for the extension.  If not supplied, it will be taken
               from HEADER_IN.  If not supplied and not in HEADER_IN, no
               EXTLEVEL will be written into the output extension.
       /NO_ABORT: Set to return to calling program instead of a RETALL
               when an I/O error is encountered.  If set, the routine will
               return  a non-null string (containing the error message) in the
               keyword MESSAGE.   If /NO_ABORT not set, then FITS_WRITE will 
               print the message and issue a RETALL
	/NO_DATA: Set if you only want FITS_WRITE to write a header.  The
		header supplied will be written without modification and
		the user is expected to write the data using WRITEU to unit
		FCB.UNIT. When FITS_WRITE is called with /NO_DATA, the user is
		responsible for the validity of the header, and must write
		the correct amount and format of the data.  When FITS_WRITE
		is used in this fashion, it will pad the data from a previously
		written extension to 2880 blocks before writting the header.

 OUTPUT KEYWORD PARAMETERS:
       MESSAGE: value of the error message for use with /NO_ABORT
	HEADER: actual output header written to the FITS file.

 NOTES:
	If the first call to FITS_WRITE is an extension, FITS_WRITE will
	automatically write a null image as the primary data unit.

	Keywords and history in the input header will be properly separated
	into the primary data unit and extension portions when constructing
	the output header (See FITS_READ for information on the internal
	Header format which separates the extension and PDU header portions).
	
 EXAMPLES:
	Write an IDL variable to a FITS file with the minimal required header.
		FITS_WRITE,'newfile.fits',ARRAY

	Write the same array as an image extension, with a null Primary data
	unit.
		FITS_WRITE,'newfile.fits',ARRAY,xtension='IMAGE'

	Write 4 additional image extensions to the same file.
		FITS_OPEN,'newfile.fits',fcb
		FITS_WRITE,fcb,data1,extname='FLUX',extver=1
		FITS_WRITE,fcb,err1,extname'ERR',extver=1
		FITS_WRITE,fcb,data2,extname='FLUX',extver=2
		FITS_WRITE,fcb,err2,extname='ERR',extver=2
		FITS_CLOSE,FCB
		
 WARNING: 
       FITS_WRITE currently does not completely update the file control block.
       When mixing FITS_READ and FITS_WRITE commands it is safer to use 
       file names, rather than passing the file control block.
 PROCEDURES USED:
	FITS_OPEN, SXADDPAR, SXDELPAR, SXPAR()
 HISTORY:
	Written by:	D. Lindler	August, 1995
	Work for variable length extensions  W. Landsman   August 1997
	Converted to IDL V5.0   W. Landsman   September 1997
	PCOUNT and GCOUNT added for IMAGE extensions   J. Graham  October 1999
       Write unsigned data types      W. Landsman   December 1999
       Pad data area with zeros not blanks  W. McCann/W. Landsman October 2000
       Return Message='' to signal normal operation W. Landsman Nov. 2000
       Ensure that required extension table keywords are in proper order
             W.V. Dixon/W. Landsman          March 2001
       Assume since V5.1, remove NaNValue keyword   W. Landsman Nov. 2002
       Removed obsolete !ERR system variable  W. Landsman Feb 2004
       Check that byte array supplied with table extension W. Landsman Mar 2004
       Make number of bytes 64bit to avoid possible overflow W.L  Apr 2006
       Asuume FITS_OPEN has opened the file with /SWAP_IF_LITTLE_ENDIAN
                         W. Landsman   September 2006
       Removes BZERO and BSCALE for floating point output, D. Lindler, Sep 2008

(See $IDLUTILS_DIR/goddard/pro/fits/fits_write.pro)

FIXPS

This program modifies an IDL-produced PostScript landscape mode file so that the output
is right side up rather than upside down. In other words, it turns a so-called seascape
file into an actual landscape file. Files that are not currently in landscape mode will
be ignored. Tested with single and multiple page PostScript output from IDL 7.0.1 and 7.1.

The program requires the `Coyote Library <http://www.idlcoyote.com/documents/programs.php>`
to be installed on your machine.

:Categories:
Graphics, Utilities

:Params:
in_filename: in, required, type=string
The name of an IDL-produced PostScript file in landscape mode.
out_filename: in, optional, type=string
The name of the fixed output PostScript file. If not provided, the input
file is overwritten. Overwritting assumes proper read/write permission in
TEMP directory and in the directory where the input file is located.

:Keywords:
a4: in, optional, type=boolean, default=0
Set this keyword if the PostScript file is using a A4 Europeran sized page.
ledger: in, optional, type=boolean, default=0
Set this keyword if the PostScript file is using a US ledger size (11 x 17 inch) page.
legal: in, optional, type=boolean, default=0
Set this keyword if the PostScript file is using a US legal size (8.5 x 14 inch) page.
letter: in, optional, type=boolean, default=0
Set this keyword if the PostScript file is using a US letter size (8.5 x 11 inch) page.
pagetype: in, optional, type=string, default="Letter"
A generic way to set the page size. A string of "LETTER", "LEDGER", "LEGAL", or "A4".
quiet: in, optional, type=boolean, default=0
Set this keyword to suppress error messages from the program.
success: out, optional, type=boolean
If this keyword is set to a named variable, then on output the variable will
return a 1 if the operation was successful, and a 0 otherwise. Using this
keyword also supresses the program's ability to "throw" an error. Informational
messages are issued about program developments, but this program will allow the
program caller to decide what to do with unsuccessful program completion.

:History:
Change History::
Written by: David W. Fanning, 6 August 2009.
Change to overwrite input file if output filename is not provided. 6 August 2009. DWF.
Incorporated checks for non-landscape mode files and files that have already been fixed. 6 August 2009. DWF.
Modified to fix multiple-page PostScript files and to work seamlessly with PS_START output. 8 August 2009. DWF.
Ran into a problem in which the PostScript file is stored in the directory pointed
to by the IDL_TMPDIR environment variable. Now check to see if the input filename
is the same as the output filename and make a change, if necessary. 22 July 2010. DWF.
Retreated to standard error handling with ERROR_MESSAGE as there are inevitable errors. 2 August 2010. DWF.
Output file was created, even if not used. Now deleting file and issuing messages to
explain why output file was not created. 1 November 2010. DWF.
Added SUCCESS and QUIET keywords. 15 Novemember 2010. DWF.
PostScript file structure changed in IDL 8. Made adjustment to find the
PageBoundingBox line. 19 Dec 2010. DWF.

:Copyright:
Copyright (c) 2009-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/fixps.pro)

FLEGENDRE

 NAME:
        FLEGENDRE
 PURPOSE:
       Compute the first M terms in a Legendre polynomial expansion.  
 EXPLANATION:
       Meant to be used as a supplied function to SVDFIT.

       This procedure became partially obsolete in IDL V5.0 with the 
       introduction of the /LEGENDRE keyword to SVDFIT and the associated 
       SVDLEG function.    However, note that, unlike SVDLEG, FLEGENDRE works
       on vector values of X.     
 CALLING SEQUENCE:
       result = FLEGENDRE( X, M)

 INPUTS:
       X - the value of the independent variable, scalar or vector
       M - number of term of the Legendre expansion to compute, integer scalar 

 OUTPUTS:
       result - (N,M) array, where N is the number of elements in X and M
               is the order.   Contains the value of each Legendre term for
               each value of X
 EXAMPLE:
       (1) If x = 2.88 and M = 3 then 
       IDL> print, flegendre(x,3)   ==>   [1.00, 2.88, 11.9416]

       This result can be checked by explicitly computing the first 3 Legendre
       terms, 1.0, x, 0.5*( 3*x^2 -1)

       (2) Find the coefficients to an M term Legendre polynomial that gives
               the best least-squares fit to a dataset (x,y)
               IDL> coeff = SVDFIT( x,y,M,func='flegendre')
       
           The coefficients can then be supplied to the function POLYLEG to 
               compute the best YFIT values for any X. 
 METHOD:
       The recurrence relation for the Legendre polynomials is used to compute
       each term.   Compare with the function FLEG in "Numerical Recipes"
       by Press et al. (1992), p. 674

 REVISION HISTORY:
       Written     Wayne Landsman    Hughes STX      April 1995                
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/flegendre.pro)

FLUX2MAG

 NAME:
     FLUX2MAG
 PURPOSE:
     Convert from flux (ergs/s/cm^2/A) to magnitudes.
 EXPLANATION:
     Use MAG2FLUX() for the opposite direction.

 CALLING SEQUENCE:
     mag = flux2mag( flux, [ zero_pt, ABwave=  ] )

 INPUTS:
     flux - scalar or vector flux vector, in erg cm-2 s-1 A-1

 OPTIONAL INPUT:
     zero_pt - scalar giving the zero point level of the magnitude.
               If not supplied then zero_pt = 21.1 (Code et al 1976)
               Ignored if the ABwave keyword is supplied

 OPTIONAL KEYWORD INPUT:
     ABwave - wavelength scalar or vector in Angstroms.   If supplied, then 
           FLUX2MAG() returns Oke AB magnitudes (Oke & Gunn 1983, ApJ, 266,
           713).

 OUTPUT:
     mag - magnitude vector.   If the ABwave keyword is set then mag
           is given by the expression 
           ABMAG = -2.5*alog10(f) - 5*alog10(ABwave) - 2.406 
             
           Otherwise, mag is given by the expression  
           mag = -2.5*alog10(flux) - zero_pt
 EXAMPLE:
       Suppose one is given wavelength and flux vectors, w (in Angstroms) and 
       f (in erg cm-2 s-1 A-1).   Plot the spectrum in AB magnitudes

       IDL> plot, w, flux2mag(f,ABwave = w), /nozero

 REVISION HISTORY:
       Written    J. Hill        STX Co.       1988
       Converted to IDL V5.0   W. Landsman   September 1997
       Added ABwave keyword    W. Landsman   September 1998

(See $IDLUTILS_DIR/goddard/pro/astro/flux2mag.pro)

FM_UNRED

 NAME:
     FM_UNRED
 PURPOSE:
     Deredden a flux vector using the Fitzpatrick (1999) parameterization
 EXPLANATION:
     The R-dependent Galactic extinction curve is that of Fitzpatrick & Massa 
     (Fitzpatrick, 1999, PASP, 111, 63; astro-ph/9809387 ).    
     Parameterization is valid from the IR to the far-UV (3.5 microns to 0.1 
     microns).    UV extinction curve is extrapolated down to 912 Angstroms.

 CALLING SEQUENCE:
     FM_UNRED, wave, flux, ebv, [ funred, R_V = , /LMC2, /AVGLMC, ExtCurve= 
                       gamma =, x0=, c1=, c2=, c3=, c4= ]
 INPUT:
      WAVE - wavelength vector (Angstroms)
      FLUX - calibrated flux vector, same number of elements as WAVE
               If only 3 parameters are supplied, then this vector will
               updated on output to contain the dereddened flux.
      EBV  - color excess E(B-V), scalar.  If a negative EBV is supplied,
               then fluxes will be reddened rather than dereddened.

 OUTPUT:
      FUNRED - unreddened flux vector, same units and number of elements
               as FLUX

 OPTIONAL INPUT KEYWORDS
      R_V - scalar specifying the ratio of total to selective extinction
               R(V) = A(V) / E(B - V).    If not specified, then R = 3.1
               Extreme values of R(V) range from 2.3 to 5.3

      /AVGLMC - if set, then the default fit parameters c1,c2,c3,c4,gamma,x0 
             are set to the average values determined for reddening in the 
             general Large Magellanic Cloud (LMC) field by Misselt et al. 
            (1999, ApJ, 515, 128)
      /LMC2 - if set, then the fit parameters are set to the values determined
             for the LMC2 field (including 30 Dor) by Misselt et al.
             Note that neither /AVGLMC or /LMC2 will alter the default value 
             of R_V which is poorly known for the LMC. 
             
      The following five input keyword parameters allow the user to customize
      the adopted extinction curve.    For example, see Clayton et al. (2003,
      ApJ, 588, 871) for examples of these parameters in different interstellar
      environments.

      x0 - Centroid of 2200 A bump in microns (default = 4.596)
      gamma - Width of 2200 A bump in microns (default  =0.99)
      c3 - Strength of the 2200 A bump (default = 3.23)
      c4 - FUV curvature (default = 0.41)
      c2 - Slope of the linear UV extinction component 
           (default = -0.824 + 4.717/R)
      c1 - Intercept of the linear UV extinction component 
           (default = 2.030 - 3.007*c2
            
 OPTIONAL OUTPUT KEYWORD:
      ExtCurve - Returns the E(wave-V)/E(B-V) extinction curve, interpolated
                 onto the input wavelength vector

 EXAMPLE:
       Determine how a flat spectrum (in wavelength) between 1200 A and 3200 A
       is altered by a reddening of E(B-V) = 0.1.   Assume an "average"
       reddening for the diffuse interstellar medium (R(V) = 3.1)

       IDL> w = 1200 + findgen(40)*50      ;Create a wavelength vector
       IDL> f = w*0 + 1                    ;Create a "flat" flux vector
       IDL> fm_unred, w, f, -0.1, fnew  ;Redden (negative E(B-V)) flux vector
       IDL> plot,w,fnew                   

 NOTES:
       (1) The following comparisons between the FM curve and that of Cardelli, 
           Clayton, & Mathis (1989), (see ccm_unred.pro):
           (a) - In the UV, the FM and CCM curves are similar for R < 4.0, but
                 diverge for larger R
           (b) - In the optical region, the FM more closely matches the
                 monochromatic extinction, especially near the R band.
       (2)  Many sightlines with peculiar ultraviolet interstellar extinction 
               can be represented with the FM curve, if the proper value of 
               R(V) is supplied.
       (3) Use the 4 parameter calling sequence if you wish to save the 
               original flux vector.
 PROCEDURE CALLS:
       CSPLINE(), POLY()
 REVISION HISTORY:
       Written   W. Landsman        Raytheon  STX   October, 1998
       Based on FMRCurve by E. Fitzpatrick (Villanova)
       Added /LMC2 and /AVGLMC keywords,  W. Landsman   August 2000
       Added ExtCurve keyword, J. Wm. Parker   August 2000
       Assume since V5.4 use COMPLEMENT to WHERE  W. Landsman April 2006

(See $IDLUTILS_DIR/goddard/pro/astro/fm_unred.pro)

FORPRINT

 NAME:
       FORPRINT
 PURPOSE:
       Print a set of vectors by looping over each index value.

 EXPLANATION:
       If W and F are equal length vectors, then the statement
               IDL> forprint, w, f   
       is equivalent to 
               IDL> for i = 0L, N_elements(w)-1 do print,w[i],f[i]    

 CALLING SEQUENCE:
       forprint, v1,[ v2, v3, v4,....v18, FORMAT = , TEXTOUT = ,STARTLINE =,
                                  SUBSET=, NUMLINE =, /SILENT, COMMENT= ] 

 INPUTS:
       V1,V2,...V18 - Arbitary IDL vectors.  If the vectors are not of
               equal length then the number of rows printed will be equal
               to the length of the smallest vector.   Up to 18 vectors
               can be supplied.

 OPTIONAL KEYWORD INPUTS:

       TEXTOUT - Controls print output device, defaults to !TEXTOUT

               textout=1       TERMINAL using /more option if available
               textout=2       TERMINAL without /more option
               textout=3       file 'forprint.prt'
               textout=4       file 'laser.tmp' 
               textout=5      user must open file
               textout =      filename (default extension of .prt)
               textout=7       Append to <program>.prt file if it exists

       COMMENT - String scalar or vector to write to the first line of output 
                file if  TEXTOUT > 2.    By default, FORPRINT will write a time
                stamp on the first line.   Use /NOCOMMENT if you don't want 
                FORPRINT to write anything in the output file.    If COMMENT
                is a vector then one line will be written for each element.
       FORMAT - Scalar format string as in the PRINT procedure.  The use
               of outer parenthesis is optional.   Ex. - format="(F10.3,I7)"
               This program will automatically remove a leading "$" from
               incoming format statements. Ex. - "$(I4)" would become "(I4)".
               If omitted, then IDL default formats are used.
       /NOCOMMENT  - Set this keyword if you don't want any comment line
               line written as the first line in a harcopy output file.
       /SILENT - Normally, with a hardcopy output (TEXTOUT > 2), FORPRINT will
                print an informational message.    If the SILENT keyword
               is set and non-zero, then this message is suppressed.
       SUBSET - Index vector specifying elements to print.   No error checking
               is done to make sure the indicies are valid.  The statement

              IDL> forprint,x,y,z,subset=s
                       is equivalent to 
              IDL> for i=0,n-1 do print, x[s[i]], y[s[i]], z[s[i]]

       STARTLINE - Integer scalar specifying the first line in the arrays
               to print.   Default is STARTLINE = 1, i.e. start at the
               beginning of the arrays.    (If a SUBSET keyword is supplied
               then STARTLINE refers to first element in the subscript vector.)
      /STDOUT - If set, the force standard output unit (=-1) if not writing 
               to a file.   This allows the FORPINT output to be captured
               in a journal file.    Only needed for non-GUI terminals 
       WIDTH - Line width for wrapping, passed onto OPENW when using hardcopy.

 OUTPUTS:
       None
 SYSTEM VARIABLES:
       If keyword TEXTOUT is not used, the default is the nonstandard 
       keyword !TEXTOUT.    If you want to use FORPRINT to write more than 
       once to the same file, or use a different file name then set 
       TEXTOUT=5, and open and close then file yourself (see documentation 
       of TEXTOPEN for more info).
       
       One way to add the non-standard system variables !TEXTOUT and !TEXTUNIT
       is to use the procedure ASTROLIB
 EXAMPLE:
       Suppose W,F, and E are the wavelength, flux, and epsilon vectors for
       a spectrum.   Print these values to a file 'output.dat' in a nice 
       format.

       IDL> fmt = '(F10.3,1PE12.2,I7)'
       IDL> forprint, F = fmt, w, f, e, TEXT = 'output.dat'

 PROCEDURES CALLED:
       TEXTOPEN, TEXTCLOSE
 REVISION HISTORY:
       Written    W. Landsman             April, 1989
       Keywords textout and format added, J. Isensee, July, 1990
       Made use of parenthesis in FORMAT optional  W. Landsman  May 1992
       Added STARTLINE keyword W. Landsman    November 1992
       Set up so can handle 18 input vectors. J. Isensee, HSTX Corp. July 1993
       Handle string value of TEXTOUT   W. Landsman, HSTX September 1993
       Added NUMLINE keyword            W. Landsman, HSTX February 1996
       Added SILENT keyword             W. Landsman, RSTX, April 1998
       Much faster printing to a file   W. Landsman, RITSS, August, 2001
       Use SIZE(/TNAME) instead of DATATYPE() W. Landsman SSAI October 2001
       Fix skipping of first line bug introduced Aug 2001  W. Landsman Nov2001
       Added /NOCOMMENT keyword, the SILENT keyword now controls only 
       the display of informational messages.  W. Landsman June 2002
       Skip PRINTF if IDL in demo mode  W. Landsman  October 2004
       Assume since V5.4 use BREAK instead of GOTO W. Landsman April 2006
       Add SUBSET keyword, warning if different size vectors passed. 
                                     P.Broos,W.Landsman. Aug 2006
       Change keyword_set() to N_elements W. Landsman  Oct 2006
       Added /STDOUT keyword  W. Landsman Oct 2006
       Fix error message for undefined variable W. Landsman  April 2007
       Added WIDTH keyword    J. Bailin  Nov 2010
       Allow multiple (vector) comment lines  W. Landsman April 2011

(See $IDLUTILS_DIR/goddard/pro/misc/forprint.pro)

FPUFIX

 NAME:
       FPUFIX

 PURPOSE:

       This is a utility routine to examine a variable and fix problems
       that will create floating point underflow errors.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Utilities

 CALLING SEQUENCE:

       fixedData = FPUFIX(data)

 ARGUMENTS:

       data :         A numerical variable to be checked for values that will cause
                      floating point underflow errors. Suspect values are set to 0.

 KEYWORDS:

       None.

 RETURN VALUE:

       fixedData:    The output is the same as the input, except that any values that
                     will cause subsequent floating point underflow errors are set to 0.

 COMMON BLOCKS:
       None.

 EXAMPLES:

       data = FPTFIX(data)

 RESTRICTIONS:

     None.

 MODIFICATION HISTORY:

       Written by David W. Fanning, from Mati Meron's example FPU_FIX. Mati's
          program is more robust that this (ftp://cars3.uchicago.edu/midl/),
          but this serves my needs and doesn't require other programs from
          Mati's library.  24 February 2006.

(See $IDLUTILS_DIR/goddard/pro/coyote/fpufix.pro)

FREBIN

 NAME:
   FREBIN

 PURPOSE:
   Shrink or expand the size of an array an arbitary amount using interpolation

 EXPLANATION: 
   FREBIN is an alternative to CONGRID or REBIN.    Like CONGRID it
   allows expansion or contraction by an arbitary amount. ( REBIN requires 
   integral factors of the original image size.)    Like REBIN it conserves 
   flux by ensuring that each input pixel is equally represented in the output
   array.       

 CALLING SEQUENCE:
   result = FREBIN( image, nsout, nlout, [ /TOTAL] )

 INPUTS:
    image - input image, 1-d or 2-d numeric array
    nsout - number of samples in the output image, numeric scalar

 OPTIONAL INPUT:
    nlout - number of lines in the output image, numeric scalar
            If not supplied, then set equal to 1

 OPTIONAL KEYWORD INPUTS:
   /total - if set, the output pixels will be the sum of pixels within
          the appropriate box of the input image.  Otherwise they will
          be the average.    Use of the /TOTAL keyword conserves surface flux.
 
 OUTPUTS:
    The resized image is returned as the function result.    If the input
    image is of type DOUBLE or FLOAT then the resized image is of the same
    type.     If the input image is BYTE, INTEGER or LONG then the output
    image is usually of type FLOAT.   The one exception is expansion by
    integral amount (pixel duplication), when the output image is the same
    type as the input image.  
     
 EXAMPLE:
     Suppose one has an 800 x 800 image array, im, that must be expanded to
     a size 850 x 900 while conserving surface flux:

     IDL> im1 = frebin(im,850,900,/total) 

     im1 will be a 850 x 900 array, and total(im1) = total(im)
 NOTES:
    If the input image sizes are a multiple of the output image sizes
    then FREBIN is equivalent to the IDL REBIN function for compression,
    and simple pixel duplication on expansion.

    If the number of output pixels are not integers, the output image
    size will be truncated to an integer.  The platescale, however, will
    reflect the non-integer number of pixels.  For example, if you want to
    bin a 100 x 100 integer image such that each output pixel is 3.1
    input pixels in each direction use:
           n = 100/3.1   ; 32.2581
          image_out = frebin(image,n,n)

     The output image will be 32 x 32 and a small portion at the trailing
     edges of the input image will be ignored.
 
 PROCEDURE CALLS:
    None.
 HISTORY:
    Adapted from May 1998 STIS  version, written D. Lindler, ACC
    Added /NOZERO, use INTERPOLATE instead of CONGRID, June 98 W. Landsman  
    Fixed for nsout non-integral but a multiple of image size  Aug 98 D.Lindler
    DJL, Oct 20, 1998, Modified to work for floating point image sizes when
		expanding the image. 
    Improve speed by addressing arrays in memory order W.Landsman Dec/Jan 2001

(See $IDLUTILS_DIR/goddard/pro/image/frebin.pro)

FSC_BASE_FILENAME

NAME:
FSC_BASE_FILENAME

PURPOSE:

The purpose of this is to extract from a long file path, the
base file name. That is, the name of the actual file without
the preceeding directory information or the final file extension.
The directory information and file extension can be obtained via
keywords. The file is named so as not to interfere with FILE_BASENAME,
which was introduced in IDL 6.0 and performs a similar function.

AUTHOR:

CATEGORY:

Utility.

CALLING SEQUENCE:

baseFilename = FSC_Base_Filename(thePath)

INPUTS:

thePath: This is the file path you wish to extract a base file name from.
It is a string variable of the sort returned from Dialog_Pickfile.

KEYWORDS:

DIRECTORY: The directory information obtained from the input file path.
The directory always ends in a directory separator character.

EXTENSION: The file extension associated with the input file path.

PATH_SEPARATOR: The string to use as a path separator. If undefined, the output
of PATH_SEP() will be used.

RETURN_VALUE:

baseFilename: The base filename, stripped of directory and file extension information.

RESTRICTIONS:

This is a quick and dirty program. It has been tested on Windows machines and *lightly*
tested on UNIX machines. Please contact me at the e-mail address above if you discover
problems.

EXAMPLE:

IDL> thePath = "C:\rsi\idl7.8\lib\jester.pro"
IDL> Print, FSC_Base_Filename(thePath, Directory=theDirectory, Extension=theExtension)
jester
IDL> Print, theDirectory
C:\rsi\idl7.8\lib\
IDL> Print, theExtension
pro

MODIFICATION HISTORY:

Written by: David W. Fanning, 31 July 2003.
Modified by KaRo, 13 Feb. 2005 to allow dots in the filename.
Added PATH_SEPARATOR keyword. 25 July 2005. DWF.
Added ability to recongnize directory by path separator in last character. 19 Sept 2005. DWF.
If directory is blank (because a relative filename was passed), set to current directory. 6 Aug 2009. DWF.
There were a couple of instances where the directory did NOT end in a path separator. Fixed. 24 Feb 2012. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_base_filename.pro)

FSC_DROPLIST

 NAME:
   FSC_DROPLIST

 PURPOSE:

   The purpose of this compound widget is to provide an alternative
   to the DROPLIST widget offered in the IDL distribution. What has
   always annoyed me about a droplist is that you can't get the current
   "value" of a droplist easily. This compound widget makes this and
   other tasks much easier.

 AUTHOR:

   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:

   General programming.

 CALLING SEQUENCE:

   droplistObj = FSC_Droplist(parent, Title='Animals: ", Value=['Dog'. 'Cat', 'Coyote'], Index=2)

   The return value of the FSC_Droplist (droplistObj in this example) is
   an object reference. Interaction with the droplist will occur through
   object methods.

 INPUT PARAMETERS:

   parent -- The parent widget ID of the compound widget. Required.

 INPUT KEYWORDS:

 Any keyword that is appropriate for the Widget_Droplist function can be used.
 In addition, these keywords are explicitly defined.

   EVENT_FUNC -- Set this keyword to the name of an Event Handler Function.
   EVENT_PRO -- Set this keyword to the name of an Event Handler Procedure.
   FORMAT -- A format specifier for the "format" of the values in the droplist.
   INDEX -- The index number of the current selection.
   SPACES -- A two-element array that indicates the number of blank spaces to be added
             to the the beginning and end of the formatted values. If a single number
             is provided, this number of blank spaces is added to both the beginning
             and the end of the value.
   TITLE -- The title of the droplist widget.
   UNAME -- The user name of the droplist widget. (Only available in IDL 5.2 and higher.)
   UVALUE -- The normal "user value" of the droplist.
   VALUE -- An array of the droplist "selections". May be any data type.

 COMMON BLOCKS:

   None.

 DEPENDENCIES:

   Requires ERROR_MESSAGE from the Coyote Library..

 EVENT STRUCTURE:

   An event is returned each time the droplist value is changed. The event structure
   is defined like this:

   event = { FSC_DROPLIST_EVENT, $ ; The name of the event structure.
             ID: 0L, $             ; The ID of the compound widget's top-level base.
             TOP: 0L, $            ; The widget ID of the top-level base of the hierarchy.
             HANDLER: 0L, $        ; The event handler ID. Filled out by IDL.
             INDEX: 0L, $          ; The index number of the current selection.
             SELECTION:Ptr_New() $ ; A pointer to the current selection "value".
             SELF:Obj_New() }      ; The object reference of the compound widget.

 PUBLIC OBJECT METHODS:

   GetID -- A function with no arguments that returns the widget identifier
      of the droplist widget.

      droplistID = droplistObj->GetID()

   GetIndex -- A function with no arguments that returns the index
      number of the current droplist selection.

      currentIndex = droplistObj->GetIndex()

   GetSelection -- A function with no arguments that returns the current
      droplist selection.

      currentSelection = droplistObj->GetSelection()

   GetUValue -- A function with no arguments that returns the "user value"
      of the compound widget i.e., the value set with the UVALUE keyword).

      myUValue = droplistObj->GetUValue()

   GetValues -- A function with no arguments that returns the "values" or
      "selections" for the droplist.

      possibleSelections = droplistObj->GetValues()

   Resize -- A procedure that sets the X screen size of the droplist. It is
      defined like this:

      PRO Resize, newSize, ParentSize=parentSize

      The "newSize" keyword is the new X screen size. If this argument is
      missing, the screen X size of the compound widget's parent is used.
      The parentSize keyword is an output keyword that returns the X screen
      size of the compound widget's parent.

      droplistObj->Resize, 400

      Note that not all devices (e.g., X Windows devices) support droplist resizing.

   SetIndex -- A procedure that sets the current droplist selection based on
      the given index. This is equivalent to Widget_Control, droplistID, Set_Droplist_Select=newIndex

      droplistObj->SetIndex, newIndex

   SetSelection -- Whereas a regular droplist widget can only be set by index
      number, this compound widget can also be set by a "selection". The new selection
      can be any data type and corresponds to one of the "values" of the droplist.

      droplistObj->SetSelection, newSelection

   SetValues -- Sets the possible selections of the droplist widget. The CurrentIndex keyword
      will allow the current index of the selection to be changed to:

      newChoices = ['dog', 'cat', 'coyote']
      droplistObj->SetValues, newChoices, CurrentIndex=2


 EXAMPLE:

   An example program is provided at the end of the FSC_DROPLIST code. To run it,
   type these commands:

      IDL> .Compile FSC_DROPLIST
      IDL> Example

 MODIFICATION HISTORY:

   Written by: David W Fanning, 17 Jan 2000. DWF.
   Added FORMAT and SPACES keywords 28 April 2000. DWF.
   Fixed a small problem with event processing when the EVENT_FUNC keyword
      was used. 29 Dec 2000. DWF.
   Attached the UNAME value to the TLB of the compound widget instead
      of to the droplist widget itself. 11 Jan 2001. DWF.
   Fixed a problem when the droplist was part of a modal widget and used the
      EVENT_PRO keyword. 27 Oct 2003. DWF.
   Added a SetValue method for setting all the values in the droplist at once. 12 Nov 2004. DWF.
   Fixed type on line 346/ 6 Feb 2008. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_droplist.pro)

FSC_FIELD

NAME:
FSC_FIELD

PURPOSE:

The purpose of this compound widget is to provide an alternative
to the CW_FIELD widget offered in the IDL distribution. One weakness
of the CW_FIELD compound widget is that the text widgets do not
look editable to the users on Windows platforms. This program
corrects that deficiency and adds some features that I think
will be helpful. For example, you can now assign an event handler
to the compound widget, ask for positive numbers only, and limit
the number of digits in a number, or the number of digits to the
right of a decimal point. The program is written as a widget object,
which allows the user to call object methods directly, affording
even more flexibility in use. This program replaces the earlier
programs FSC_INPUTFIELD and COYOTE_FIELD.

The program consists of a label widget next to a one-line text widget.
The "value" of the compound widget is shown in the text widget. If the
value is a number, it will not be possible (generally) to type
alphanumeric values in the text widget. String values behave like
strings in any one-line text widget.

AUTHOR:

CATEGORY:

General programming.

TYPICAL CALLING SEQUENCE:

fieldID = FSC_FIELD(parent, Title="X Size:", Value=256, Object=fieldObject, Digits=3)

INPUT PARAMETERS:

parent -- The parent widget ID of the compound widget. Required.

INPUT KEYWORDS:

COLUMN Set this keyword to have the Label widget above the Text widget.
The default is to have the Label widget in a row with the Text widget.

CR_ONLY Set this keyword if you only want Carriage Return events returned to
your event handler. If this keyword is not set, all events are returned.
Setting this keyword has no effect unless either the EVENT_PRO or
EVENT_FUNC keyword is used.

DECIMAL Set this keyword to the number of digits to the right of the decimal
point in floating point or double precision numbers. Ignored for STRING values.

DIGITS Set this keyword to the number of digits permitted in integer numbers.

EVENT_FUNC Set this keyword to the name of an event handler function. If this
keyword is undefined and the Event_Pro keyword is undefined,
all compound widget events are handled internally and not
passed on to the parent widget.

EVENT_PRO Set this keyword to the name of an event handler procedure. If this
keyword is undefined and the Event_Func keyword is undefined,
all compound widget events are handled internally and not
passed on to the parent widget.

FIELDFONT The font name for the text in the text widget.

FRAME Set this keyword to put a frame around the compound widget.

FOCUS_EVENTS Set this keyword to enable event generation for keyboard focus
events. Ignored unless EVENT_FUNC or EVENT_PRO keywords are specified.

HIGHLIGHT Set this keyword to highlight the existing text if the widget gain
the keyboard focus. This keyword MUST be set for tabbing to work naturally
in IDL 6.2 and higher.

LABEL_LEFT Set this keyword to align the text on the label to the left.

LABEL_RIGHT Set this keyword to align the text on the label to the right.

LABELFONT The font name for the text in the label widget.

LABELSIZE The X screen size of the label widget.

NAME A string containing the name of the object. The default is ''.

NOEDIT Set this keyword to allow no user editing of the input text widget.

NONSENSITIVE Set this keyword to make the input text widget non-sensitive.

POSITIVE Set this keyword if you want only positive numbers allowed.

SCR_XSIZE The X screen size of the compound widget.

SCR_YSIZE The Y screen size of the compound widget.

TITLE The string text placed on the label widget.

UNDEFINED Set this keyword to the value to use for "undefined" values. If
not set, then !Value.F_NAN is used for numerical fields and a
NULL string is used for string fields. This applies to values
obtained with the GET_VALUE method or the GET_VALUE function.

UVALUE A user value for any purpose.

VALUE The "value" of the compound widget. Any type of integer, floating, or string
variable is allowed. The data "type" is determined automatically from the
value supplied with this keyword. Be sure you set the type appropriately for
your intended use of the value.

XSIZE The X size of the text widget in the usual character units.

OUTPUT KEYWORDS:

OBJECT Set this keyword to a named variable to receive the compound widget's
object reference. This is required if you wish to call methods on the object.
Note that the object reference is also available in the event structure
generated by the widget object. Note that the object reference will be
necessary if you want to get or set values in the compound widget.

COMMON BLOCKS:

None.

RESTRICTIONS:

Requires DBLTOSTR from the Coyote Library:
http://www.idlcoyote.com/programs/dbltostr.pro

EVENT STRUCTURE:

All events are handled internally unless either the Event_Pro or Event_Func
keywords are used to assign an event handler to the compound widget. By
default all events generated by the text widget are passed to the assigned
event handler. If you wish to receive only Carriage Return events, set the
CR_Only keyword.

event = { FSC_FIELD_EVENT, $ ; The name of the event structure.
ID: 0L, $ ; The ID of the compound widget's top-level base.
TOP: 0L, $ ; The widget ID of the top-level base of the hierarchy.
HANDLER: 0L, $ ; The event handler ID. Filled out by IDL.
OBJECT: Obj_New(), $ ; The "self" object reference. Provided so you can call methods.
VALUE: Ptr_New(), $ ; A pointer to the widget value.
TYPE:"" ; A string indicating the type of data in the VALUE field.
}

Note that if the field is "empty", the VALUE will be a pointer
to an undefined variable. You should check this value before you
use it. You code will look something like this:

IF N_Elements(*event.value) EQ 0 THEN $
Print, 'Current Value UNDEFINED.' ELSE $
Print, 'Current Value: ', *event.value

GETTING and SETTING VALUES:

Almost all the properties of the widget can be obtained or set via
the object's GetProperty and SetProperty methods (described below).
Traditional compound widgets have the ability to get and set the "value"
of the compound widget identifier (e.g., fieldID in the calling
sequence above). Unfortunately, it is impossible to retreive a variable
in this way when the variable is undefined. In practical terms, this
means that the undefined variable must be set to *something*. You can
determine what that something is with the UNDEFINED keyword, or I will set
it to !VALUES.F_NAN for numerical fields and to the null string for string
fields. In any case, you will have to check for undefined variables before
you try to do something with the value. For a numerical field, the code
might look something like this:

fieldID = FSC_FIELD(parent, Title="X Size:", Value=256, Object=fieldObject, Digits=3)
currentValue = fieldObject->Get_Value()
IF Finite(currentValue) EQ 0 THEN Print, 'Value is Undefined' ELSE Print, currentValue

Additional examples are provided in the numerical example fields in Example Program below.

Setting the value of the compound widget is the same as calling the Set_Value
method on the object reference. In other words, these two statements are equivalent.

fieldObject->Set_Value, 45.4
Widget_Control, fieldID, Set_Value=45.4

The data type of the value is determined from the value itself. Be sure you set it appropriately.

OBJECT PROCEDURE METHODS:

GetProperty -- This method allows various properties of the widget to be
returned via output keywords. The keywords that are available are:

CR_Only -- A flag, if set, means only report carriage return events.
DataType -- The data type of the field variable.
Decimal -- Set this keyword to the number of digits to the right of the decimal
point in FLOATVALUE and DOUBLEVALUE numbers.
Digits -- Set this keyword to the number of digits permitted in INTERGERVALUE and LONGVALUE numbers.
Event_Func -- The name of the event handler function.
Event_Pro -- The name of the event handler function.
Has_Focus -- Set to 1 if the text widget currently has the keyboard focus.
Highlight -- The highlight flag.
NoEdit -- The NoEdit flag.
NonSensitive -- The NonSensitive flag.
Undefined -- The "value" of any undefined value.
UValue -- The user value assigned to the compound widget.
Value -- The "value" of the compound widget.
Name -- A scalar string name of the object.

Resize -- This method allows you to resize the compound widget's text field.
The value parameter is an X screen size for the entire widget. The text
widget is sized by using the value obtained from this value minus the
X screen size of the label widget.

objectRef->Resize, screen_xsize_value

Set_Value -- This method allows you to set the "value" of the field. It takes
one positional parameter, which is the value.

objectRef->Set_Value, 5

SetProperty -- This method allows various properties of the widget to be
set via input keywords. The keywords that are available are:

CR_Only -- Set this keyword if you only want Carriage Return events.
Decimal -- Set this keyword to the number of digits to the right of the decimal
point in FLOAT and DOUBLE numbers.
Digits -- Set this keyword to the number of digits permitted in INTERGER and LONG numbers.
Event_Func -- Set this keyword to the name of an Event Function.
Event_Pro -- Set this keyword to the name of an Event Procedure.
Highlight -- Set this keyword to highlight the existing text
when the widget gets the keyboard focus
LabelSize -- The X screen size of the Label Widget.
Name -- A scalar string name of the object. (default = '')
NoEdit -- Set this keyword to make the text widget uneditable
NonSensitive -- Set this keyword to make the widget nonsensitive
Scr_XSize -- The X screen size of the text widget.
Scr_YSize -- The Y screen size of the text widget.
Title -- The text to go on the Label Widget.
UValue -- A user value for any purpose.
Value -- The "value" of the compound widget.
XSize -- The X size of the Text Widget.

SetTabNext -- This method allows you to specify which field to go to when a TAB character
is typed in the text widget. See the Example program below for an example of how to
use this method.

OBJECT FUNCTIONS METHODS:

Get_Value -- Returns the "value" of the field. No parameters. Will be undefined
if a "number" field is blank. Should be checked before using:

IF N_Elements(objectRef->Get_Value()) NE 0 THEN Print, Value is: ', objectRef->Get_Value()

GetID -- Returns the widget identifier of the compound widget's top-level base.
(The first child of the parent widget.) No parameters.

GetLabelSize -- Returns the X screen size of the label widget. No parameters.

GetTextID -- Returns the widget identifier of the compound widget's text widget.
No parameters.

GetTextSize -- Returns the X screen size of the text widget. No parameters.

PRIVATE OBJECT METHODS:

Although there is really no such thing as a "private" method in IDL's
object implementation, some methods are used internally and not meant to
be acessed publicly. Here are a few of those methods. I list them because
it may be these private methods are ones you wish to override in subclassed
objects.

MoveTab -- This method moves the focus to the widget identified in the "next" field,
which must be set with the SetTabNext method. No parameters. Called automatically
when a TAB character is typed in the text widget.

Text_Events -- The main event handler method for the compound widget. All
text widget events are processed here.

ReturnValue -- This function method accepts a string input value and converts
it to the type of data requested by the user.

Validate -- This function method examines all text input and removes unwanted
characters, depending upon the requested data type for the field. It makes it
impossible, for example, to type alphanumeric characters in an INTEGER field.

EXAMPLE:

An example program is provided at the end of the FSC_FIELD code. To run it,
type these commands:

IDL> .Compile FSC_Field
IDL> Example

MODIFICATION HISTORY:

Written by: David W. Fanning, 18 October 2000. Based heavily on an earlier
FSC_INPUTFIELD program and new ideas about the best way to write
widget objects.
Added LABEL_LEFT, LABEL_RIGHT, and UNDEFINED keywords. 29 Dec 2000. DWF.
Modified the way the value is returned in the GET_VALUE method and the
GET_VALUE function. Modified Example program to demonstrate. 30 Dec 2000. DWF.
Added NOEDIT and NONSENSITIVE keywords, with corresponding SETEDIT and SETSENNSITIVE
methods. 19 Jan 2001. DWF.
Actually followed through with the changes I _said_" I made 29 Dec 2000. (Don't ask....) 13 June 2001. DWF.
Added GetTextSize and GetLabelSize methods for obtaining the X screen
size of the text and label widgets, respectively. 21 July 2001. DWF.
Fixed a problem in SetProperty method where I was setting self.xsize, which doesn't exist. 24 April 2002. DWF.
Small modification to the SetEdit method. 6 August 2003. DWF.
Added Highlight keyword. Ported Focus_Events keyword from
fsc_inputfield.pro. Updated documentation. 17 November
2004. DWF and Benjamin Hornberger
Added Has_Focus keyword to the GetProperty method. 18 November
2004. Benjamin Hornberger
Fixed bug in GetProperty method (set value to *self.undefined if
*self.value is undefined. 24 Feb 2004. Benjamin Hornberger
Modified FOCUS_EVENTS keyword handling so that *all* focus events are now
passed to specified event handlers. Check event.select to see if the
widget is gaining or losing focus. 10 August 2005. DWF.
Added new tabbing functionality, introduced in IDL 6.2. To use tabbing
functionality natually, the HIGHTLIGHT keywords must be set.
See included EXAMPLE program for details. 10 August 2005. DWF.
Added functionality to covert double precision values to strings properly. 30 Nov 2005. DWF.
Set the default fonts to be the current widget font, rather than the default widget font. 4 Oct 2008. DWF.
Fixed a problem with validating a float or double value when it was written with
exponential notation. 2 April 2010. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_field.pro)

FSC_FILESELECT

 NAME:
   FSC_FILESELECT

 PURPOSE:

   The purpose of this compound widget is to provide a means
   by which the user can type or select a file name. The
   program is written as an "object widget", meaning that
   the guts of the program is an object of class FSC_FILESELECT.
   This is meant to be an example of the obvious advantages of
   writing compound widget programs as objects.

 AUTHOR:

   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:

   General programming.

 CALLING SEQUENCE:

   filenameID = FSC_FileSelect(parent)

 INPUT PARAMETERS:

   parent -- The parent widget ID of the compound widget. Required.

 INPUT KEYWORDS:

   Event_Pro -- The event handler procedure for this compound widget.By default: "".
   Event_Func -- The event handler function for this compound widget. By default: "".

      If neither EVENT_PRO or EVENT_FUNC is defined, program events are handled internally by the compound widget.

   DirectoryName -- The initial name of the directory. By defaut: current directory.
   Filename -- The initial file name in the filename text widget.
   Filter -- The file filter. By default: "*".
   Frame -- Set this keyword for a frame around the compound widget.
   LabelFont -- The font for the label widget. By default: "".
   LabelName -- The text on the label widgt. By default: "Filename: ".
   LabelSize -- The X screen size of the label widget. By default: 0.
   MustExist -- A flag that indicates selected files must exist. By default: 0.
   NoMaxSize -- A flag to prohibit automatic text widget sizing. By default: 0.

     If this keyword is not set, the compound widget will automatically resize itself to
     the largest widget in its parent base widget. It will do this by changing the size of
     the text widgets holding the file and directory names.

   Read -- Set this keyword to have file selection for reading a file. By default: 1.
   SelectDirectory -- The default directory for file selection. In other words, this is the
     default directory for DIALOG_PICKFILE, which is accessed via the BROWSE buttons.
   SelectFont -- The font for the "Browse" button. By default: "".
   SelectTitle -- The title bar text on the file selection dialog. By default: "Select a File...".
   TextFont -- The font for the filename text widget. By default: "".
   UValue -- User value for any purpose.
   Write -- Set this keyword to open a file for writing. By default: 0.
   XSize -- The X size of the text widget holding the filename. By default: StrLen(filename) * 1.5 > 40.

 OUTPUT KEYWORDS:

   ObjectRef -- Assign this keyword to an output variable that will hold the internal object reference.
                With the object reference you can call object methods to easily change many properties of
                the compound widget.

 COMMON BLOCKS:

   None.

 RESTRICTIONS:

   Requires the folling files from the Coyote Library:

      http://www.idlcoyote.com/programs/error_message.pro

 EVENT STRUCTURE:

   All events are handled internally unless either the Event_Pro or Event_Func
   keywords are used to assign an event handler to the compound widget. All events
   generated by the text widgets are passed to the assigned event handler.

   event = { CW_FILESELECT, $     ; The name of the event structure.
             ID: 0L, $            ; The ID of the compound widget's top-level base.
             TOP: 0L, $           ; The widget ID of the top-level base of the hierarchy.
             HANDLER: 0L, $       ; The event handler ID. Filled out by IDL.
             Basename: "", $      ; The base filename without directory specifiers.
             Filename: "", $      ; The fully qualified filename.
             Directory: "", $     ; The name of the current file directory.
           }

 EXAMPLE:

   An example program is provided at the end of the FSC_FILESELECT code. To run it,
   type these commands:

      IDL> .Compile fsc_fileselect
      IDL> Example

   Or, if you want to obtain the object reference, type this:

      IDL> Example, theObject

   Now you can call the object's methods. For example:

      IDL theObject->SetProperty, XSize=150

 GETTING and SETTING VALUES:

   So as not to disrupt the accepted paradigm in using compound widgets, you
   can use the return value of the FSC_FILESELECT function with WIDGET_CONTROL to
   get and set the "value" of the widget.

       Widget_Control, filenameID, Set_Value='C:\RSI\IDL52\DATA\cyclone.dat'

   The program will automatically separate the file name portion of the value
   from the directory portion and put things in the correct text widgets.

   Similarly, you can get the "value" of the widget:

       Widget_Control, filenameID, Get_Value=theValue
       Print, theValue

           C:\RSI\IDL52\DATA\cyclone.dat

   The return value is the fully qualified file path to the file.

 USING OBJECT METHODS to CHANGE PROGRAM PROPERTIES:

   If you obtain the object reference, you have a great deal more control
   over the properties of the compound widget. You obtain the object reference
   by calling the function like this:

      filenameID = FSC_FILESELECT(parent, ObjectRef=theObject)

 OBJECT PROCEDURE METHODS:

   GetProperty -- This method allows various properties of the widget to be
       returned via output keywords. The keywords that are available are:

      DirectoryName -- The current directory.
      Event_Func -- The name of the event handler function for this compound widget.
      Event_Pro -- The name of the event handler procedure for this compound widget.
      Filename -- The current base filename.
      Filter -- The current file filter.
      LabelName -- The text on the label widget.
      LabelSize -- The X screen size of the label widget.
      MustExist -- A flag that indicates selected files must exist to be selected.
      Parent -- The parent widget of the compound widget.
      Read=read -- The file selection for reading flag.
      SelectTitle -- The title bar text on the file selection dialog.
      TLB -- The top-level base of the compound widget.
      UValue -- The user value of the compound widget.
      Write -- The file selection for writing flag.
      XSize -- The X size of the text widget holding the filename.

   LabelSize -- This method makes sure that the directory name and file name labels
      are the same size. Normally, this procedure is called internally. No parameters.

   MatchSize -- This method resizes the compound widget so that it is as long as the
      the longest widget in the parent base widget. This is done automatically upon
      realization unless the NOMAXSIZE keyword is set. The method aids in writing
      resizeable widget programs.

   SetProperty -- This method allows various properties of the widget to be
       set via input keywords. The keywords that are available are:

      DirectoryName -- The current directory.
      Event_Func -- The name of the event handler function for this compound widget.
      Event_Pro -- The name of the event handler procedure for this compound widget.
      Filename -- The current base filename.
      Filter -- The current file filter.
      LabelName -- The text on the label widget.
      LabelSize -- The X screen size of the label widget.
      MustExist -- A flag that indicates selected files must exist to be selected.
      Read -- The file selection for reading flag.
      SelectTitle -- The title bar text on the file selection dialog.
      UValue -- The user value of the compound widget.
      Write -- The file selection for writing flag.
      XSize -- The X size of the text widget holding the filename.

   TextSelect - Allows you to create a selection in filename text widget. See the
                documentation for the SET_TEXT_SELECT keyword to Widget_Control.

      selection -- A two-element array containing the starting position and selection length.

 OBJECT FUNCTION METHODS:

      GetFileName -- Returns the fully qualified filename. No parameters.

      GetTLB -- Returns the top-level base ID of the compound widget. No Parameters.

      Inspect_DirectoryName -- Inspects the directory name for correctness. Requires one positional parameter.

        directoryName -- The name of the directory from the directory text widget.
        textSelection -- The current text selection position.

        At the moment all this does is remove any blank characters from either
        end of the directory name and makes sure the last character of the directory
        name does not end in a subdirectory specifier (except for VMS).

     Inspect_Filename -- Inspects the file name for correctness. Requires one positional parameter.

        filename -- The name of the file from the filename text widget.
        textSelection -- The current text selection position.

        At the moment all this does is remove any blank characters from either
        end of the file name

 MODIFICATION HISTORY:

   Written by: David W. Fanning, 21 NOV 1999.
   Fixed bug in File Name selection button. 18 MAR 2000. DWF.
   Fixed an error in which directory the Browse buttons should start
       searching. 29 SEP 2000. DWF.
   Previously returned events only for typing in text widgets. Now
       Browse button events are also returned. 29 SEP 2000. DWF.
   Fixed a bug in setting the file filter. 29 SEP 2000. DWF.
   Removed the Directory Browse button 10 AUG 2002. DWF.
   Added ERROR_MESSAGE to error handling. 10 AUG 2002. DWF.
   Changed the ability to specify a file filter as a string array, instead
       of just as a scalar string. This required the use of a pointer, which
       meant that I had to remove the FILTER field from the CW_FILESELECT
       event structure to avoid likely memory leakage. This is a dangerous
       change because it means programs that relied on this (I expect there
       are very, very few) will break and it goes against my philosopy of
       keeping my programs backward compatible. Let me know if you have
       problems. In testing, I discoved no problems in my own code. 31 OCT 2002. DWF.
   Fixed a problem with DIALOG_PICKFILE that sometimes allowed users to change
       directories without selecting a file. 3 Nov 2002. DWF.
   Fixed a problem with widget resizing with the help of Bob Portman that had plagued
       me from the beginning. Thanks, Bob! 5 August 2003. DWF
   Added TEXTSELECT method. 5 Aug 2003. DWF.
   Had to add FORWARD_FUNCTION statement to get error handler compiled when using
       DIRECTORY keyword. 24 Nov 2003. DWF.
   Fixed a problem with too many events going to an event handler specified with
       the EVENT_PRO or EVENT_FUNC keyword from the text widget. Now only Carriage
       Return events are passed on to the user-specified event handler. 8 July 2004. DWF.
   Replace all "\" characters with "/" characters in directory names. 8 Januay 2006. DWF.
   Set the default fonts to be the current widget font, rather than the default widget font. 4 Oct 2008. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_fileselect.pro)

FSC_PLOTWINDOW

NAME:
FSC_PLOTWINDOW

PURPOSE:

The purpose of this compound widget is to create a resizeable
"plot window" inside a larger "page window". I'm not sure it
has any value except as a utility routine for the PostScript
configuration object FSC_PSCONFIG__DEFINE, but it's a neat
program anyway. :-)

AUTHOR:

CATEGORY:

Utility routine for FSC_PSCONFIG__DEFINE.

CALLING SEQUENCE:

plotwindowObject = CW_PlotWindow(parent)

REQUIRED INPUT PARAMETERS:

parent - The parent base widget of this compound widget.

RETURN VALUE:

plotwindowObject - The object reference of the compound widget.

KEYWORDS:

COLOR - If set, display the window in "color". This is the default on 24-bit devices.
DEBUG - Set this keyword to turn traceback error handling on in the error handling code.
EVENT_PRO - The event procedure for the widget. Required for events to be generated. Otherwise, all events are handled internally.
LANDSCAPE - If set, display the page in landscape mode. Otherwise the page is display in portrait mode.
PAGESIZE - The "pagesize" of the widget. Possible values are: "LETTER", "LEDGER", "LEGAL", "A4", and "DISPLAY".
UNITS - A string indicating INCHES or CENTIMETER units. DEVICE units represented by a null string, "".
UVALUE - A user value for the caller of this program.
WINDOWCOLOR - A three-element array specifying the background window color (RGB).
WINDOWSIZE - The size of the "window" on the page. A four-element array of normalized coordinates in the form [x0, y0, x1, y1].

EVENT STRUCTURE:

The event structure that is returned from this compound widget is defined like this,
where the sizes and offsets locate the target "window" on the page in normalized units:

event = {ID:0L, TOP:0L, HANDLER:0L, XSize:0.0, YSize:0.0, XOffset:0.0, YOffset:0.0}

MODIFICATIONS:

Written by David Fanning, 31 January 2000.
Fixed a small bug that prevented it working on Macintosh computers. 26 Sept 2000. DWF.
Added a "DISPLAY" page size, so the program can be used to position
plots and other graphics in a display window. The "page area" will
have the same aspect ratio is the current graphics window. 17 March 2001. DWF.
Changed some of the tolerances for "closeness" from 0.1 to 0.025 to allow smaller
sizing for colorbars and other small objects. 6 July 2005. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_plotwindow.pro)

FSC_PSCONFIG__DEFINE

NAME:
FSC_PSCONFIG__DEFINE

PURPOSE:

The purpose of this program is to implement an object that
can keep track of--and allow the user to change--the current
configuration of the PostScript device.

AUTHOR:

CATEGORY:

General programming.

DOCUMENTATION:

Complete documentation for the FSC_PSCONFIG object, including
keyword and method descriptions, and example programs using the object
can be found on the Coyote's Guide to IDL Programming web page:

http://www.idlcoyote.com/programs/docs/fsc_psconfig.html

Or, if you would prefer, you can download a self-contained PDF file:

http://www.idlcoyote.com/programs/docs/fsc_psconfig.pdf

KEYWORDS:

Any keyword accepted by the FSC_PSCONFIG object can be used with
this program. Here are a few of the most popular keywords.

Bits_per_Pixel - The number of image bits saved for each image pixel: 2, 4, or 8. The default is 8.
Color - Set this keyword to select Color PostScript output. Turned on by default.
Decomposed - Set this keyword to 0 to select indexed color and to 1 to select decomposed color.
DefaultSetup - Set this keyword to the "name" of a default style. Current styles (you can easily
create and add your own to the source code) are the following:

"System (Portrait)" - The normal "default" system set-up. Also, "System".
"System (Landscape)" - The normal "default" landscape system set-up.
"Centered (Portrait)" - The window centered on the page. Also, "Center" or "Centered".
"Centered (Landscape)" - The window centered on the landscape page. Also, "Landscape".
"Square (Portrait)" - A square plot, centered on the page.
"Square (Landscape)" - A square plot, centered on the landscape page.
"Figure (Small)" - A small encapsulated figure size, centered on page. Also, "Encapsulated" or "Encapsulate".
"Figure (Large)" - A larger encapsulated figure size, centered on page. Also, "Figure".
"Color (Portrait)" - A "centered" plot, with color turned on. Also, "Color".
"Color (Landscape)" - A "centered" landscape plot, with color turned on.

Directory - Set this keyword to the name of the starting directory. The current directory is used by default.
Encapsulated - Set this keyword to select Encapsulated PostScript output. Turned off by default.
European - This keyword has been depreciated in favor of METRIC.
Filename - Set thie keyword to the name of the PostScript file. The default is "idl.ps".
Inches - Set this keyword to indicate sizes and offsets are in inches as opposed to centimeters. Set by Metric keyword by default.
Landscape - Set this keyword to select Landscape page output. Portrait page output is the default.
Language_Level - Set this keyword to select the Language Level interpreter. Default is 1.
Metric - Set this keyword to indicate metric mode (i.e., A4 page and centimeter units). Turned off by default.
PageType - Set this keyword to the "type" of page. Possible values are:
"Letter" - 8.5 by 11 inches. (Default, unless the Metric keyword is set.)
"Legal" - 8.5 by 14 inches.
"Ledger" - 11 by 17 inches.
"A4" - 21.0 by 29.7 centimeters. (Default, if the Metric keyword is set.)
XOffset - Set this keyword to the X Offset. Uses "System (Portrait)" defaults. (Note: offset calculated from lower-left corner of page.)
XSize - Set this keyword to the X size of the PostScript "window". Uses "System (Portrait)" defaults.
YOffset - Set this keyword to the Y Offset. Uses "System (Portrait)" defaults. (Note: offset calculated from lower-left corner of page.)
YSize - Set this keyword to the Y size of the PostScript "window". Uses "System (Portrait)" defaults.

In addition, the following keywords can be used:

CANCEL -- An output keyword that will be set to 1 if the user
chooses the Cancel button on the form. It will be 0 otherwise.

FONTINFO -- Set this keyword is you wish to have font information
appear on the form. The default is to not include font information.

FONTTYPE -- Set this keyword to a named variable that will indicate
the user's preference for font type. Values will be -1 (Hershey fonts),
0 (hardware fonts), and 1 (true-type fonts). This keyword will always
return -1 unless the FONTINFO keyword has also been set.

GROUP_LEADER -- Set this keyword to a widget identifier of the widget
you wish to be a group leader for this program.

EXAMPLE:

A simple sequence of using the object would look something like this:

psObject = Obj_New("FSC_PSCONFIG")
psObject->GUI
psKeywords = psObject->GetKeywords()
thisDevice = !D.Name
Set_Plot, 'PS'
Device, _Extra=psKeywords
cgImage, image
Device, /Close_File
Set_Plot, thisDevice
Obj_Destroy, psObject

Note that the object can also be called from the PS_CONFIG interface:

psKeywords = PSConfig()

OTHER PROGRAMS NEEDED:

The following programs are required to run this one:

fsc_droplist.pro
fsc_fileselect.pro
fsc_field.pro
fsc_plotwindow

MODIFICATIONS:

Written by David W. Fanning, 31 January 2000.
Added capability to call GUI methods when the current graphics device
doesn't support windows. Device is restored when the GUI exits. 11 May 2000. DWF.
Changed the default value for the Color keyword to 1. 16 May 2000. DWF.
Fixed a bug where filename changed when switching Setups. 8 AUG 2000. DWF.
Fixed a bug when saving setup in Landscape mode. 8 AUG 2000. DWF.
Added the ability to Get and Set the object's name via the SetProperty
and a very abbreviated GetProperty method. Also added a GetName method. 26 SEP 2000. DWF.
Fixed a problem in which the proper configuration was not restored if in Landscape mode. 20 Nov 2000. DWF.
Made a number of modifications at the request of Martin Schultz. 4 Dec 2000. DWF.
Fixed a bug when setting file and directory names with the SetProperty method. 18 Dec 2000. DWF.
Fixed a small problem in initializing the page size properly. 3 Jan 2001. DWF.
Corrected a problem that resulted from a change to FSC_DROPLIST. 6 Jan 2001. DWF.
Added the ability to restore the font type instead of always reverting to !P.Font. 7 Jan 2001. DWF.
Increased the length of the file/directory name fields. 7 Jan 2001. DWF.
Fixed another problem with Landscape mode interacting with A4 paper size. 7 Jan 2001. DWF.
Seems I only half fixed the previous problem. :-( 26 April 2001. DWF.
Forgot to update program to reflect change in FSC_FIELD. Fixed 26 April 2001. DWF.
Changed BOOKMAN keyword to BKMAN to avoid conflict with BOOKSTYLE keyword. 26 April 2001. DWF.
Modified the System Defaults to say "None" if none is used. Improved documentation. 10 September 2001. DWF.
Added the ability to specify a filename at the same time as a Default Setup. 10 September 2001. DWF.
Fixed a small problem in not setting new page sizes appropriately. 22 May 2002. DWF.
Fixed a problem that occurred when the Accept button was not named "Accept". 6 May 2003.DWF.
Whoops! I was a bit overly agressive on that last fix. :-( 17 July 2003. DWF.
Fixed a problem with setting page types when using the DEFAULTSETUP keyword. 31 July 2003. DWF.
Fixed a problem with turning encapsulation on in the GUI. Renamed ENCAPSULATE keyword ENCAPSULATED
to avoid obvious errors. 31 July 2003. DWF.
Removed obsolete STR_SEP and replaced with STRSPLIT. 27 Oct 2004. DWF.
Now honoring EUROPEAN keyword when setting system default setups in the INIT method. 12 Nov 2004. DWF.
Added CMYK output option 24 August 2007. Assumes LANGUAGE_LEVEL=2 printer. L. Anderson.
Fixed a problem with the filename on WINDOWS computers coming back with forward slashes instead of
backward slashes. 20 May 2008. DWF.
Modified the program to return as the default, ISOLATIN1=1. 18 July 2008. DWF.
Fixed a problem with filenames when a DEFAULTSETUP was used with it. 12 Nov 2008. DWF.
Changed default window size when LANDSCAPE keyword is set. 10 April 2009. DWF.
Changed the default window size for PORTRAIT mode to be a bit larger. 10 April 2009. DWF.
Updated for IDL 7.1 and 24-bit color PostScript support. 24 May 2009. DWF.
Added PAGETYPE field to returned structure to allow PostScript page type to be determined. 8 August 2009. DWF.
Fixed a problem with 24-bit color support that allowed only IDL 7 versions to work correctly. 20 Sept 2009. DWF.
Added a LANGUAGE_LEVEL keyword. 13 Dec 2010. DWF.
Added the FONTYPE value to the keyword return structure. 14 Dec 2010. DWF.
Modified the return structure to turn landscape mode off and set offsets to zero if in
encapsulated mode. 19 Feb 2011. DWF.
Changes to handle inability to create raster files from PS encapsulated files in
landscape mode. Also removed changes of 19 Feb 2011 as no longer needed. 26 Aug 2011. DWF.
The PAGETYPE was not getting set properly in the return keywords when the Metric
option was selected on the GUI. 12 October 2011. DWF.
The program now remembers the last directory you used and will start in that
directory, unless told otherwise. 26 Oct 2011. DWF.
Parsing of full filename failing. Fixed 27 Oct 2011. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_psconfig__define.pro)

FSC_PS_SETUP__DEFINE

 NAME:
   FSC_PS_SETUP__DEFINE

 PURPOSE:

    The purpose of FSC_PS_SETUP__DEFINE is to define a structure that is
    use with PS_START and PS_END, programs that make it easy to set-up
    for and close a PostScript file. The programs work in close conjunction
    with PSCONFIG, another program from the Coyote Library.

 AUTHOR:

   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:

       Graphics, File Output, PostScript

 CALLING SEQUENCE:

       Used internally in PS_START and PS_END.

 COMMON BLOCKS:

       _$FSC_PS_START_   Contains the PS_STRUCT structure for communication between
                         PS_START and PS_END.

 MODIFICATION HISTORY:

       Separated from PS_START file, 7 April 2009, by David W. Fanning.
       Added PAGETYPE field to structure. 8 August 2009. DWF.
       Changes to handle inability to create raster files from PS encapsulated files in 
           landscape mode. Added "encapsulated" field to structure. 26 Aug 2011. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/fsc_ps_setup__define.pro)

FTAB_DELROW

 NAME:
       FTAB_DELROW
 PURPOSE:
       Delete rows of data from a FITS ASCII or binary table extension

 CALLING SEQUENCE:
       ftab_delrow, filename, rows, EXTEN_NO =, NEWFILE = ] 

 INPUTS-OUPUTS
       filename - scalar string giving name of the FITS file containing an
               ASCII or binary table extension. 
 
       rows  -  scalar or vector, specifying the row numbers to delete
               First row has index 0.   If a vector, it will be sorted and
               duplicates will be removed

 OPTIONAL KEYWORD INPUTS:
       EXTEN_NO - scalar integer specifying which extension number to process
               Default is to process the first extension
       NEWFILE - scalar string specifying the name of the new output FITS file
               FTAB_DELROW will prompt for this parameter if not supplied

 EXAMPLE:
       Compress the first extension of a FITS file 'test.fits' to include 
       only non-negative values in the 'FLUX' column

       ftab_ext,'test.fits','flux',flux       ;Obtain original flux vector
       bad = where(flux lt 0)                 ;Find negative fluxes
       ftab_delrow,'test.fits',bad,new='test1.fits'  ;Delete specified rows

 RESTRICTIONS:
       Does not work for variable length binary tables

 PROCEDURES USED:
       FITS_CLOSE, FITS_OPEN, FITS_READ, FITS_WRITE, FTDELROW, TBDELROW        

 REVISION HISTORY:                                           
       Written   W. Landsman        STX Co.     August, 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Use COPY_LUN if V5.6 or later     W. Landsman   February 2003
       Assume since V5.6, COPY_LUN available   W. Landsman   Sep 2006

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftab_delrow.pro)

FTAB_EXT

 NAME:
       FTAB_EXT
 PURPOSE:
       Routine to extract columns from a FITS (binary or ASCII) table. 

 CALLING SEQUENCE:
       FTAB_EXT, name_or_fcb, columns, v1, [v2,..,v9, ROWS=, EXTEN_NO= ]
 INPUTS:
       name_or_fcb - either a scalar string giving the name of a FITS file 
               containing a (binary or ASCII) table, or an IDL structure 
               containing as file control block (FCB) returned by FITS_OPEN 
               If FTAB_EXT is to be called repeatedly on the same file, then
               it is quicker to first open the file with FITS_OPEN, and then
               pass the FCB structure to FTAB_EXT
       columns - table columns to extract.  Can be either 
               (1) String with names separated by commas
               (2) Scalar or vector of column numbers

 OUTPUTS:
       v1,...,v30 - values for the columns.   Up to 30 columns can be extracted

 OPTIONAL INPUT KEYWORDS:
       ROWS -  scalar or vector giving row number(s) to extract
               Row numbers start at 0.  If not supplied or set to
               -1 then values for all rows are returned
       EXTEN_NO - Extension number to process.   If not set, then data is
               extracted from the first extension in the file (EXTEN_NO=1)

 EXAMPLES:
       Read wavelength and flux vectors from the first extension of a 
       FITS file, 'spec.fit'.   Using FTAB_HELP,'spec.fit' we find that this
       information is in columns named 'WAVELENGTH' and 'FLUX' (in columns 1
       and 2).   To read the data

       IDL> ftab_ext,'spec.fit','wavelength,flux',w,f
               or
       IDL> ftab_ext,'spec.fit',[1,2],w,f
       
 PROCEDURES CALLED:
       FITS_READ, FITS_CLOSE, FTINFO, FTGET(), TBINFO, TBGET()
 HISTORY:
       version 1        W.   Landsman         August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Improve speed processing binary tables  W. Landsman   March 2000
       Use new FTINFO calling sequence  W. Landsman   May 2000  
       Don't call fits_close if fcb supplied W. Landsman May 2001 
       Use STRSPLIT to parse column string  W. Landsman July 2002 
       Cleanup pointers in TBINFO structure  W. Landsman November 2003
       Avoid EXECUTE() if V6.1 or later  W. Landsamn   December 2006
       Assume since V6.1  W. Landsman   June 2009
       Read up to 30 columns  W.L. Aug 2009

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftab_ext.pro)

FTAB_HELP

 NAME:
       FTAB_HELP
 PURPOSE:
       Describe the columns of a FITS binary or ASCII table extension(s).

 CALLING SEQUENCE:
       FTAB_HELP, filename, [ EXTEN_No = , TEXTOUT= ]
               or
       FTAB_HELP, fcb, [EXTEN_No=, TEXTOUT= ]

 INPUTS:
       filename - scalar string giving name of the FITS file.  
       fcb - FITS control block returned by a previous call to FITS_OPEN

 OPTIONAL KEYWORD INPUTS:
       EXTEN_NO - integer scalar or vector specifying which FITS extensions 
               to display.    Default is to display all FITS extension.
       TEXTOUT - scalar number (0-7) or string (file name) determining
               output device (see TEXTOPEN).  Default is TEXTOUT=1, output 
               to the user's terminal    

 EXAMPLE:
       Describe the columns in the second and fourth extensions of a FITS 
       file spec.fits and write the results to a file 'spec24.lis'

       IDL> ftab_help,'spec.fits',exten=[2,4],t='spec24.lis'

 SYSTEM VARIABLES:
        Uses the non-standard system variables !TEXTOUT and !TEXTUNIT
       which must be defined (e.g. with ASTROLIB) before compilation
 NOTES:
       The behavior of FTAB_HELP was changed in August 2005 to display
       all extensions by default, rather than just the first extension
 PROCEDURES USED:
       FITS_READ, FITS_CLOSE, FITS_OPEN, FTHELP, TBHELP, TEXTOPEN, TEXTCLOSE
 HISTORY:
       version 1  W. Landsman    August 1997
       Corrected documentation W. Landsman   September 1997
       Don't call fits_close if fcb supplied W. Landsman May 2001 
       Default now is to display all extensions, EXTEN keyword can now
        be a vector   W. Landsman Aug 2005

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftab_help.pro)

FTAB_PRINT

 NAME:
       FTAB_PRINT
 PURPOSE:
       Print the contents of a FITS (binary or ASCII) table extension.
 EXPLANATION:
       User can specify which rows or columns to print

 CALLING SEQUENCE:
       FTAB_PRINT, filename, columns, rows, 
                   [ TEXTOUT=, FMT=, EXTEN_NO= NUM_HEADER_LINES ]

 INPUTS:
       filename - scalar string giving name of a FITS file containing a 
               binary or ASCII table
       columns - string giving column names, or vector giving
               column numbers (beginning with 1).  If a string 
               supplied then column names should be separated by comma's.
               if not supplied, then all columns are printed.
               If set to '*' then all columns are printed in table format 
               (1 row per line, binary tables only).
       rows - (optional) vector of row numbers to print (beginning with 0).  
               If not supplied or set to scalar, -1, then all rows
               are printed.
 OPTIONAL KEYWORD INPUT:
       EXTEN_NO - Extension number to read.   If not set, then the first 
               extension is printed (EXTEN_NO=1)
       FMT = Format string for print display (binary tables only).   If not
               supplied, then any formats in the TDISP keyword fields will be
               used, otherwise IDL default formats.    For ASCII tables, the
               format used is always as stored in the FITS table.
       NUM_HEADER_LINES - Number of lines to display the column headers (default
               = 1).  By setting NUM_HEADER_LINES to an integer larger than 1,
               one can avoid truncation of the headers.   In addition, setting 
               NUM_HEADER_LINES will display commented lines indicating
               a FORMAT for reading the data, and a suggested call to 
              readfmt.pro.    Works for binary tables only
       NVAL_PER_LINE - The maximum number of values displayed from a 
               multivalued column when printing in table format.   Default = 6
       TEXTOUT - scalar number (0-7) or string (file name) determining
               output device (see TEXTOPEN).  Default is TEXTOUT=1, output 
               to the user's terminal    
 EXAMPLE:
       (1) Print all rows of the first 5 columns of the first extension of the
       file 'wfpc.fits'
               IDL> ftab_print,'vizier.fits',indgen(5)+1
 
       (2) Print all columns of the first row to a file 'vizier.dat' in 
       'table' format
               IDL> ftab_print,'vizier.fits',t='vizier.dat','*',0     
 SYSTEM VARIABLES:
       Uses the non-standard system variables !TEXTOUT and !TEXTUNIT
       which must be defined (e.g. with ASTROLIB) prior to compilation.
 PROCEDURES USED:
       FITS_CLOSE, FITS_OPEN, FITS_READ, FTPRINT, TBPRINT
 HISTORY:
       version 1  W. Landsman    August 1997
       Check whether data exists   W. Landsman    Feb 2007
       Check whether extension exists  W. Landsman  Mar 2010
       Added NUM_HEADER_LINES, NVAL_PER_LINE keywords for binary tables 
                  W. Landsman Apr 2010

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftab_print.pro)

FTADDCOL

 NAME:
      FTADDCOL
 PURPOSE:
      Routine to add a field to a FITS ASCII table

 CALLING SEQUENCE:
      ftaddcol, h, tab, name, idltype, [ tform, tunit, tscal, tzero, tnull ]

 INPUTS:
      h - FITS table header.  It will be updated as appropriate
      tab - FITS table array.  Number of columns will be increased if
               neccessary.
      name - field name, scalar string
      idltype - idl data type (as returned by SIZE function) for field,
               For string data (type=7) use minus the string length.

 OPTIONAL INPUTS:
       tform - format specification 'qww.dd' where q = A, I, E, or D
       tunit - string giving physical units for the column.
       tscal - scale factor
       tzero - zero point for field
       tnull - null value for field

       Use '' as the value of tform,tunit,tscal,tzero,tnull if you want
       the default or no specification of them in the table header.

 OUTPUTS:
       h,tab - updated to allow new column of data

 PROCEDURES USED:
       FTINFO, FTSIZE, GETTOK(), SXADDPAR
 HISTORY:
       version 1  D. Lindler   July, 1987
       Converted to IDL V5.0   W. Landsman   September 1997
       Updated call to new FTINFO   W. Landsman   April 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftaddcol.pro)

FTCREATE

 NAME:
       FTCREATE
 PURPOSE:
       Create a new (blank) FITS ASCII table and header with specified size.

 CALLING SEQUENCE:
       ftcreate, maxcols, maxrows, h, tab

 INPUTS:
       maxcols - number of character columns allocated, integer scalar
       maxrows - maximum number of rows allocated, integer scalar

 OUTPUTS:
       h - minimal FITS Table extension header, string array
 OPTIONAL OUTPUT:
       tab - empty table, byte array 
 HISTORY:
       version 1  D. Lindler   July. 87
       Converted to IDL V5.0   W. Landsman   September 1997
       Make table creation optional, allow 1 row table, add comments to 
       required FITS keywords    W. Landsman    October 2001

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftcreate.pro)

FTDELCOL

 NAME:
	FTDELCOL
 PURPOSE:
	Delete a column of data from a FITS table

 CALLING SEQUENCE:
	ftdelcol, h, tab, name

 INPUTS-OUPUTS
	h,tab - FITS table header and data array.  H and TAB will
		be updated with the specified column deleted

 INPUTS:
	name - Either (1) a string giving the name of the column to delete
		or (2) a scalar giving the column number to delete

 EXAMPLE:
	Suppose it has been determined that the F7.2 format used for a field
	FLUX in a FITS table is insufficient.  The old column must first be 
	deleted before a new column can be written with a new format.

	flux = FTGET(h,tab,'FLUX')       ;Save the existing values
	FTDELCOL,h,tab,'FLUX'            ;Delete the existing column            
	FTADDCOL,h,tab,'FLUX',8,'F9.2'   ;Create a new column with larger format
	FTPUT,h,tab,'FLUX',0,flux        ;Put back the original values

 REVISION HISTORY:                                           
	Written   W. Landsman        STX Co.     August, 1988
	Adapted for IDL Version 2, J. Isensee, July, 1990
	Converted to IDL V5.0   W. Landsman   September 1997
       Updated call to new FTINFO   W. Landsman  May 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftdelcol.pro)

FTDELROW

 NAME:
       FTDELROW
 PURPOSE:
       Delete a row of data from a FITS table

 CALLING SEQUENCE:
       ftdelrow, h, tab, rows

 INPUTS-OUPUTS
       h,tab - FITS table header and data array.  H and TAB will
               be updated on output with the specified row(s) deleted.
       rows  -  scalar or vector, specifying the row numbers to delete
               This vector will be sorted and duplicates removed by FTDELROW

 EXAMPLE:
       Compress a table to include only non-negative flux values

       flux = FTGET(h,tab,'FLUX')       ;Obtain original flux vector
       bad = where(flux lt 0)           ;Find negative fluxes
       FTDELROW,h,tab,bad               ;Delete rows with negative fluxes

 PROCEDURE:
       Specified rows are deleted from the data array, TAB.  The NAXIS2
       keyword in the header is updated.

 PROCEDURES USED:
       sxaddpar

 REVISION HISTORY:                                           
       Written   W. Landsman        STX Co.     August, 1988
       Checked for IDL Version 2, J. Isensee, July, 1990
       Converted to IDL V5.0   W. Landsman   September 1997
       Assume since V5.4, use BREAK instead of GOTO  W. Landsman April 2006

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftdelrow.pro)

FTGET

 NAME:
      FTGET 
 PURPOSE:
      Function to return value(s) from specified column in a FITS ASCII table

 CALLING SEQUENCE
      values = FTGET( h, tab, field, [ rows, nulls ] )
                    or
      values = FTGET( ft_str, tab, field. [rows, nulls]
 INPUTS:
      h - FITS ASCII extension header (e.g. as returned by FITS_READ)
                            or
      ft_str - FITS table structure extracted from FITS header by FTINFO
                Use of the IDL structure will improve processing speed
      tab - FITS ASCII table array (e.g. as returned by FITS_READ)
      field - field name or number

 OPTIONAL INPUTS:
      rows -  scalar or vector giving row number(s)
               Row numbers start at 0.  If not supplied or set to
               -1 then values for all rows are returned

 OUTPUTS:
       the values for the row are returned as the function value.
       Null values are set to 0 or blanks for strings.

 OPTIONAL OUTPUT:
       nulls - null value flag of same length as the returned data.
               It is set to 1 at null value positions and 0 elsewhere.
               If supplied then the optional input, rows, must also 
               be supplied.

 EXAMPLE:
       Read the columns labeled 'WAVELENGTH' and 'FLUX' from the second
       (ASCII table) extension of a FITS file 'spectra.fit'

       IDL> fits_read,'spectra.fit',tab,htab,exten=2     ;Read 2nd extension
       IDL> w = ftget( htab, tab,'wavelength')      ;Wavelength vector
       IDL> f = ftget( htab, tab,'flux')            ;Flux vector

       Slightly more efficient would be to first call FTINFO
       IDL> ftinfo, htab, ft_str                     ;Extract structure
       IDL> w = ftget(ft_str, tab,'wavelength')      ;Wavelength vector
       IDL> f = ftget(ft_str, tab,'flux')            ;Flux vector

 NOTES:
       (1) Use the higher-level procedure FTAB_EXT to extract vectors 
               directly from the FITS file.
       (2) Use FTAB_HELP or FTHELP to determine the columns in a particular
               ASCII table.
 HISTORY:
       coded by D. Lindler  July, 1987
       Always check for null values    W. Landsman          August 1990
       More informative error message  W. Landsman          Feb. 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Allow structure rather than FITS header  W. Landsman   May 2000
       No case sensitivity in TTYPE name      W. Landsman   February 2002

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftget.pro)

FTHELP

 NAME:
       FTHELP
 PURPOSE:
       Routine to print a description of a FITS ASCII table extension

 CALLING SEQUENCE:
       FTHELP, H, [ TEXTOUT = ]

 INPUTS:
       H - FITS header for ASCII table extension, string array

 OPTIONAL INPUT KEYWORD
       TEXTOUT - scalar number (0-7) or string (file name) determining
               output device (see TEXTOPEN).  Default is TEXTOUT=1, output 
               to the user's terminal    

 NOTES:
       FTHELP checks that the keyword XTENSION  equals 'TABLE' in the FITS
               header.

 SYSTEM VARIABLES:
       Uses the non-standard system variables !TEXTOUT and !TEXTUNIT
       which must be defined (e.g. with ASTROLIB) prior to compilation.
 PROCEDURES USED:
       REMCHAR, SXPAR(), TEXTOPEN, TEXTCLOSE, ZPARCHECK

 HISTORY:
       version 1  W. Landsman  Jan. 1988
       Add TEXTOUT option, cleaner format  W. Landsman   September 1991
       TTYPE value can be longer than 8 chars,  W. Landsman  August 1995
       Remove calls to !ERR, some vectorization  W. Landsman  February 2000 
       Slightly more compact display  W. Landsman  August 2005

(See $IDLUTILS_DIR/goddard/pro/fits_table/fthelp.pro)

FTHMOD

 NAME:
       FTHMOD
 PURPOSE:
       Procedure to modify header information for a specified field
       in a FITS table.

 CALLING SEQUENCE:
       fthmod, h, field, parameter, value
       
 INPUT:
       h - FITS header for the table
       field - field name or number
       parameter - string name of the parameter to modify.  Choices
               include:
                       TTYPE - field name
                       TUNIT - physical units for field (eg. 'ANGSTROMS')
                       TNULL - null value (string) for field, (eg. '***')
                       TFORM - format specification for the field
                       TSCAL - scale factor
                       TZERO - zero offset
               User should be aware that the validity of the change is
               not checked.  Unless you really know what you are doing,
               this routine should only be used to change field names,
               units, or another user specified parameter.
       value - new value for the parameter.  Refer to the FITS table
               standards documentation for valid values.

 EXAMPLE:
      Change the units for a field name "FLUX" to "Janskys" in a FITS table
        header,h

      IDL> FTHMOD, h, 'FLUX', 'TUNIT','Janskys' 
 METHOD:
       The header keyword <parameter><field number> is modified
       with the new value.
 HISTORY:
       version 1, D. Lindler  July 1987
       Converted to IDL V5.0   W. Landsman   September 1997
       Major rewrite to use new FTINFO call   W. Landsman   May 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/fthmod.pro)

FTINFO

 NAME:
       FTINFO
 PURPOSE:
       Return an informational structure from a FITS ASCII table header.
 CALLING SEQUENCE:
       ftinfo,h,ft_str, [Count = ]

 INPUTS:
       h - FITS ASCII table header, string array

 OUTPUTS:
       ft_str - IDL structure with extracted info from the FITS ASCII table
                header.   Tags include
        .tbcol - starting column position in bytes
        .width - width of the field in bytes
        .idltype - idltype of field.
                       7 - string, 4- real*4, 3-integer, 5-real*8
        .tunit - string unit numbers
        .tscal - scale factor
        .tzero - zero point for field
        .tnull - null value for the field
        .tform - format for the field
        .ttype - field name

 OPTIONAL OUTPUT KEYWORD:
       Count - Integer scalar giving number of fields in the table
 PROCEDURES USED:
       GETTOK(), SXPAR()
 NOTES:
       This procedure underwent a major revision in May 2000, and **THE
       NEW CALLING SEQUENCE IS INCOMPATIBLE WITH THE OLD ONE **
 HISTORY:
       D. Lindler  July, 1987
       Converted to IDL V5.0   W. Landsman   September 1997
       Major rewrite, return structure   W. Landsman   April 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftinfo.pro)

FTKEEPROW

 NAME:
	FTKEEPROW
 PURPOSE:
	Subscripts (and reorders) a FITS table.  A companion piece to FTDELROW.

 CALLING SEQUENCE:
	ftkeeprow, h, tab, subs

 INPUT PARAMETERS:
	h    = FITS table header array
	tab  = FITS table data array
	subs = subscript array of FITS table rows.  Works like any other IDL
		subscript array (0 based, of course).

 OUTPUT PARAMETERS:
	h and tab are modified

 MODIFICATION HISTORY:
	Written by R. S. Hill, ST Sys. Corp., 2 May 1991.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftkeeprow.pro)

FTPRINT

  NAME:
      FTPRINT
  PURPOSE:
       Procedure to print specified columns and rows of a FITS table

 CALLING SEQUENCE:
       FTPRINT, h, tab, columns, [ rows, TEXTOUT = ]

 INPUTS:
       h - Fits header for table, string array
       tab - table array 
       columns - string giving column names, or vector giving
               column numbers (beginning with 1).  If string 
               supplied then column names should be separated by comma's.
       rows - (optional) vector of row numbers to print.  If
               not supplied or set to scalar, -1, then all rows
               are printed.

 OUTPUTS:
       None

 OPTIONAL INPUT KEYWORDS:
       TEXTOUT controls the output device; see the procedure TEXTOPEN

 SYSTEM VARIABLES:
       Uses nonstandard system variables !TEXTOUT and !TEXTOPEN
       These will be defined (using ASTROLIB) if not already present.
       Set !TEXTOUT = 3 to direct output to a disk file.   The system
       variable is overriden by the value of the keyword TEXTOUT

 EXAMPLES:

       ftprint,h,tab,'STAR ID,RA,DEC'    ;print id,ra,dec for all stars
       ftprint,h,tab,[2,3,4],indgen(100) ;print columns 2-4 for 
                                         ;first 100 stars
       ftprint,h,tab,text="stars.dat"    ;Convert entire FITS table to
                                         ;an ASCII file named STARS.DAT

 PROCEDURES USED:
       FTSIZE, FTINFO, TEXTOPEN, TEXTCLOSE

 RESTRICTIONS: 
       (1) Program does not check whether output length exceeds output
               device capacity (e.g. 80 or 132).
       (2) Column heading may be truncated to fit in space defined by
               the FORMAT specified for the column
       (3) Program does not check for null values

 HISTORY:
       version 1  D. Lindler Feb. 1987
       Accept undefined values of rows, columns   W. Landsman August 1997
       New FTINFO calling sequence    W. Landsman   May 2000
       Parse scalar string with STRSPLIT   W. Landsman  July 2002
       Fix format display of row number  W. Landsman March 2003
       Fix format display of row number again  W. Landsman May 2003

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftprint.pro)

FTPUT

 NAME:
       FTPUT
 PURPOSE:
       Procedure to add or update a field in an FITS ASCII table
 CALLING SEQUENCE:
       FTPUT, htab, tab, field, row, values, [ nulls ]

 INPUTS:
       htab - FITS ASCII table header string array
       tab - FITS ASCII table array (e.g. as read by READFITS)
       field - string field name or integer field number
       row -  either a non-negative integer scalar giving starting row to 
               update, or a non-negative integer vector specifying rows to 
               update.   FTPUT will append a new row to a table if the value 
               of 'row' exceeds the number of rows in the tab array    
       values - value(s) to add or update.   If row is a vector
               then values must contain the same number of elements.

 OPTIONAL INPUT:
       nulls - null value flag of same length as values.
               It should be set to 1 at null value positions
               and 0 elsewhere.

 OUTPUTS:
       htab,tab will be updated as specified.

 EXAMPLE:
       One has a NAME and RA  and Dec vectors for 500 stars with formats A6,
       F9.5 and F9.5 respectively.   Write this information to an ASCII table 
       named 'star.fits'.

       IDL> FTCREATE,24,500,h,tab       ;Create table header and (empty) data
       IDL> FTADDCOL,h,tab,'RA',8,'F9.5','DEGREES'   ;Explicity define the
       IDL> FTADDCOL,h,tab,'DEC',8,'F9.5','DEGREES'  ;RA and Dec columns
       IDL> FTPUT,h,tab,'RA',0,ra       ;Insert RA vector into table
       IDL> FTPUT,h,tab,'DEC',0,dec       ;Insert DEC vector into table
       IDL> FTPUT, h,tab, 'NAME',0,name   ;Insert NAME vector with default
       IDL> WRITEFITS,'stars.fits',tab,h ;Write to a file
   
      Note that (1) explicit formatting has been supplied for the (numeric)
      RA and Dec vectors, but was not needed for the NAME vector, (2) A width
      of 24 was supplied in FTCREATE based on the expected formats (6+9+9),
      though the FT* will adjust this value as necessary, and (3) WRITEFITS
      will create a minimal primary header  
 NOTES:
       (1) If the specified field is not already in the table, then FTPUT will
       create a new column for that field using default formatting.   However,
        FTADDCOL should be called prior to FTPUT for explicit formatting.

 PROCEDURES CALLED
       FTADDCOL, FTINFO, FTSIZE, SXADDPAR, SXPAR()
 HISTORY:
       version 1  D. Lindler July, 1987
       Allow E format         W. Landsman          March 1992
       Write in F format if E format will overflow    April 1994
       Update documentation W. Landsman   January 1996
       Allow 1 element vector  W. Landsman   March 1996
       Adjust string length to maximum of input string array   June 1997
       Work for more than 32767 elements August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Updated call to the new FTINFO   W. Landsman   May 2000
       Fix case where header does not have any columns yet W.Landsman Sep 2002
       Assume since V5.2, omit fstring() call  W. Landsman April 2006

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftput.pro)

FTSIZE

 NAME:
       FTSIZE
 PURPOSE:
       Procedure to return the size of a FITS ASCII table.

 CALLING SEQUENCE:
       ftsize,h,tab,ncols,rows,tfields,ncols_all,nrows_all, [ERRMSG = ]

 INPUTS:
       h - FITS ASCII table header, string array
       tab - FITS table array, 2-d byte array

 OUTPUTS:
       ncols - number of characters per row in table
       nrows - number of rows in table
       tfields - number of fields per row
       ncols_all - number of characters/row allocated (size of tab)
       nrows_all - number of rows allocated

 OPTIONAL OUTPUT KEYWORD:
       ERRMSG  = If this keyword is present, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.  
 HISTORY
       D. Lindler  July, 1987
       Fix for 1-row table,  W. Landsman    HSTX,     June 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Added ERRMSG keyword   W. Landsman   May 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftsize.pro)

FTSORT

NAME:
FTSORT
PURPOSE:
Sort a FITS ASCII table according to a specified field

CALLING SEQUENCE:
FTSORT,h,tab,[field, REVERSE = ] ;Sort original table header and array
or
FTSORT,h,tab,hnew,tabnew,[field, REVERSE =] ;Create new sorted header

INPUTS:
H - FITS header (string array)
TAB - FITS table (byte array) associated with H. If less than 4
parameters are supplied, then H and TAB will be updated to
contain the sorted table

OPTIONAL INPUTS:
FIELD - Field name(s) or number(s) used to sort the entire table.
If FIELD is a vector then the first element is used for the
primary sort, the second element is used for the secondary
sort, and so forth. (A secondary sort only takes effect when
values in the primary sort field are equal.) Character fields
are sorted using the ASCII collating sequence. If omitted,
the user will be prompted for the field name.

OPTIONAL OUTPUTS:
HNEW,TABNEW - Header and table containing the sorted tables

EXAMPLE:
Sort a FITS ASCII table by the 'DECLINATION' field in descending order
Assume that the table header htab, and array, tab, have already been
read (e.g. with READFITS or FITS_READ):

IDL> FTSORT, htab, tab,'DECLINATION',/REVERSE
OPTIONAL INPUT KEYWORD:
REVERSE - If set then the table is sorted in reverse order (maximum
to minimum. If FIELD is a vector, then REVERSE can also be
a vector. For example, REVERSE = [1,0] indicates that the
primary sort should be in descending order, and the secondary
sort should be in ascending order.

EXAMPLE:
SIDE EFFECTS:
A HISTORY record is added to the table header.
REVISION HISTORY:
Written W. Landsman June, 1988
Converted to IDL V5.0 W. Landsman September 1997
New FTINFO calling sequence, added REVERSE keyword, allow secondary sorts
W. Landsman May 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/ftsort.pro)

FXADDPAR

 NAME: 
       FXADDPAR
 Purpose     : 
       Add or modify a parameter in a FITS header array.
 Explanation : 
       This version of FXADDPAR will write string values longer than 68 
       characters using the FITS continuation convention described at 
       http://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/ofwg_recomm/r13.html
 Use         : 
       FXADDPAR, HEADER, NAME, VALUE, COMMENT
 Inputs      : 
       HEADER  = String array containing FITS header.  The maximum string
                 length must be equal to 80.  If not defined, then FXADDPAR
                 will create an empty FITS header array.

       NAME    = Name of parameter.  If NAME is already in the header the
                 value and possibly comment fields are modified. Otherwise a
                 new record is added to the header.  If NAME is equal to
                 either "COMMENT" or "HISTORY" then the value will be added to
                 the record without replacement.  In this case the comment
                 parameter is ignored.

       VALUE   = Value for parameter.  The value expression must be of the
                 correct type, e.g. integer, floating or string.
                 String values of 'T' or 'F' are considered logical
                 values unless the /NOLOGICAL keyword is set.  If the value is
                 a string and is "long" (more than 69 characters), then it 
                 may be continued over more than one line using the OGIP 
                 CONTINUE standard.

 Opt. Inputs : 
       COMMENT = String field.  The '/' is added by this routine.  Added
                 starting in position 31.  If not supplied, or set equal to ''
                 (the null string), then any previous comment field in the
                 header for that keyword is retained (when found).
 Outputs     : 
       HEADER  = Updated header array.
 Opt. Outputs: 
       None.
 Keywords    : 
       BEFORE  = Keyword string name.  The parameter will be placed before the
                 location of this keyword.  For example, if BEFORE='HISTORY'
                 then the parameter will be placed before the first history
                 location.  This applies only when adding a new keyword;
                 keywords already in the header are kept in the same position.

       AFTER   = Same as BEFORE, but the parameter will be placed after the
                 location of this keyword.  This keyword takes precedence over
                 BEFORE.

       FORMAT  = Specifies FORTRAN-like format for parameter, e.g. "F7.3".  A
                 scalar string should be used.  For complex numbers the format
                 should be defined so that it can be applied separately to the
                 real and imaginary parts.      If not supplied, then the IDL
                 default formatting is used, except that double precision is
                 given a format of G19.12.

       /NOCONTINUE = By default, FXADDPAR will break strings longer than 68 
                characters into multiple lines using the continuation
                convention.    If this keyword is set, then the line will
                instead be truncated to 68 characters.    This was the default
                behaviour of FXADDPAR prior to December 1999.  

      /NOLOGICAL = If set, then the values 'T' and 'F' are not interpreted as
                logical values, and are simply added without interpretation.

	ERRMSG	 = If defined and passed, then any error messages will be
		   returned to the user in this parameter rather than
		   depending on the MESSAGE routine in IDL, e.g.

			ERRMSG = ''
			FXADDPAR, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
       DETABIFY(), FXPAR(), FXPARPOS()
 Common      : 
       None.
 Restrictions: 
       Warning -- Parameters and names are not checked against valid FITS
       parameter names, values and types.

       The required FITS keywords SIMPLE (or XTENSION), BITPIX, NAXIS, NAXIS1,
       NAXIS2, etc., must be entered in order.  The actual values of these
       keywords are not checked for legality and consistency, however.

 Side effects: 
       All HISTORY records are inserted in order at the end of the header.

       All COMMENT records are also inserted in order at the end of the
       header, but before the HISTORY records.  The BEFORE and AFTER keywords
       can override this.

       All records with no keyword (blank) are inserted in order at the end of
       the header, but before the COMMENT and HISTORY records.  The BEFORE and
       AFTER keywords can override this.

       All other records are inserted before any of the HISTORY, COMMENT, or
       "blank" records.  The BEFORE and AFTER keywords can override this.

       String values longer than 68 characters will be split into multiple
       lines using the OGIP CONTINUE convention, unless the /NOCONTINUE keyword
       is set.    For a description of the CONTINUE convention see    
       http://fits.gsfc.nasa.gov/registry/continue_keyword.html
 Category    : 
       Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
       William Thompson, Jan 1992, from SXADDPAR by D. Lindler and J. Isensee.
       Differences include:

               * LOCATION parameter replaced with keywords BEFORE and AFTER.
               * Support for COMMENT and "blank" FITS keywords.
               * Better support for standard FITS formatting of string and
                 complex values.
               * Built-in knowledge of the proper position of required
                 keywords in FITS (although not necessarily SDAS/Geis) primary
                 headers, and in TABLE and BINTABLE extension headers.

       William Thompson, May 1992, fixed bug when extending length of header,
       and new record is COMMENT, HISTORY, or blank.
 Written     : 
       William Thompson, GSFC, January 1992.
 Modified    : 
       Version 1, William Thompson, GSFC, 12 April 1993.
               Incorporated into CDS library.
       Version 2, William Thompson, GSFC, 5 September 1997
               Fixed bug replacing strings that contain "/" character--it
               interpreted the following characters as a comment.
       Version 3, Craig Markwardt, GSFC,  December 1997
               Allow long values to extend over multiple lines
	Version 4, D. Lindler, March 2000, modified to use capital E instead
		of a lower case e for exponential format.
       Version 4.1 W. Landsman April 2000, make user-supplied format uppercase
       Version 4.2 W. Landsman July 2002, positioning of EXTEND keyword
       Version 5, 23-April-2007, William Thompson, GSFC
       Version 6, 02-Aug-2007, WTT, bug fix for OGIP long lines
       Version 6.1, 10-Feb-2009, W. Landsman, increase default format precision
       Version 6.2  30-Sep-2009, W. Landsman, added /NOLOGICAL keyword
 Version     : 
       Version 6.2, 30-Sep-2009

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxaddpar.pro)

FXBADDCOL

 NAME: 
	FXBADDCOL
 PURPOSE     : 
	Adds a column to a binary table extension.
 EXPLANATION : 
	Modify a basic FITS binary table extension (BINTABLE) header array to
	define a column.
 USE         : 
	FXBADDCOL, INDEX, HEADER, ARRAY  [, TTYPE [, COMMENT ]]
 INPUTS      : 
	HEADER	= String array containing FITS extension header.
	ARRAY	= IDL variable used to determine the data size and type
		  associated with the column.  If the column is defined as
		  containing variable length arrays, then ARRAY must be of the
		  maximum size to be stored in the column.
 Opt. Inputs : 
	TTYPE	= Column label.
	COMMENT = Comment for TTYPE
 Outputs     : 
	INDEX	= Index (1-999) of the created column.
	HEADER	= The header is modified to reflect the added column.
 Opt. Outputs: 
	None.
 Keywords    : 
	VARIABLE= If set, then the column is defined to contain pointers to
		  variable length arrays in the heap area.
	DCOMPLEX= If set, and ARRAY is complex, with the first dimension being
		  two (real and imaginary parts), then the column is defined as
		  double-precision complex (type "M").     This keyword is
		  only needed prior to IDL Version 4.0, when the double 
		  double complex datatype was unavailable in IDL
	BIT	= If passed, and ARRAY is of type byte, then the column is
		  defined as containg bit mask arrays (type "X"), with the
		  value of BIT being equal to the number of mask bits.
	LOGICAL	= If set, and array is of type byte, then the column is defined
		  as containing logical arrays (type "L").
	NO_TDIM	= If set, then the TDIMn keyword is not written out to the
		  header.  No TDIMn keywords are written for columns containing
		  variable length arrays.
	TUNIT	= If passed, then corresponding keyword is added to header.
	TSCAL	= Same.
	TZERO	= Same.
	TNULL	= Same.
	TDISP	= Same.
	TDMIN	= Same.
	TDMAX	= Same.
	TDESC	= Same.
	TCUNI	= Same.
	TROTA	= Same.
	TRPIX	= Same.
	TRVAL	= Same.
	TDELT	= Same.
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBADDCOL, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	FXADDPAR, FXPAR
 Common      : 
	None.
 Restrictions: 
	Warning: No checking is done of any of the parameters defining the
	values of optional FITS keywords.

	FXBHMAKE must first be called to initialize the header.

	If ARRAY is of type character, then it must be of the maximum length
	expected for this column.  If a character string array, then the
	largest string in the array is used to determine the maximum length.

	The DCOMPLEX keyword is ignored if ARRAY is not double-precision.
	ARRAY must also have a first dimension of two representing the real and
	imaginary parts.

	The BIT and LOGICAL keywords are ignored if ARRAY is not of type byte.
	BIT takes precedence over LOGICAL.

 Side effects: 
	If the data array is multidimensional, then a TDIM keyword is added to
	the header, unless either NO_TDIM or VARIABLE is set.

	No TDIMn keywords are written out for bit arrays (format 'X'), since
	the dimensions would refer to bits, not bytes.

 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Jan 1992.
	W. Thompson, Feb 1992, changed from function to procedure.
	W. Thompson, Feb 1992, modified to support variable length arrays.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 4, William Thompson, GSFC, 30 December 1994
		Added keyword TCUNI.
	Version 5, Wayne Landsman, GSFC, 12 Aug 1997
		Recognize double complex IDL datatype
       Version 6, Wayne Landsman, GSFC. C. Yamauchi (ISAS) 23 Feb 2006
               Support 64bit integers
       Version 7, C. Markwardt, GSFC, Allow unsigned integers, which
               have special TSCAL/TZERO values.  Feb 2009
       Version 8,  P.Broos (PSU), Wayne Landsman (GSFC) Mar 2010
               Do *not* force TTYPE* keyword to uppercase
 Version     :
       Version 8, Mar 2010

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbaddcol.pro)

FXBCLOSE

 NAME: 
	FXBCLOSE
 Purpose     : 
	Close a FITS binary table extension opened for read.
 Explanation : 
	Closes a FITS binary table extension that had been opened for read by
	FXBOPEN.
 Use         : 
	FXBCLOSE, UNIT
 Inputs      : 
	UNIT	= Logical unit number of the file.
 Opt. Inputs : 
	None.
 Outputs     : 
	None.
 Opt. Outputs: 
	None.
 Keywords    : 
	ERRMSG	  = If defined and passed, then any error messages will be
		    returned to the user in this parameter rather than
		    depending on the MESSAGE routine in IDL.  If no errors are
		    encountered, then a null string is returned.  In order to
		    use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBCLOSE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	None.
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The file must have been opened with FXBOPEN.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Feb. 1992.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
 Version     :
       Version 3, 23 June 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbclose.pro)

FXBCOLNUM()

 NAME: 
	FXBCOLNUM()
 Purpose     : 
	Returns a binary table column number.
 Explanation : 
	Given a column specified either by number or name, this routine will
	return the appropriate column number.
 Use         : 
	Result = FXBCOLNUM( UNIT, COL )
 Inputs      : 
	UNIT	= Logical unit number corresponding to the file containing the
		  binary table.
	COL	= Column in the binary table, given either as a character
		  string containing a column label (TTYPE), or as a numerical
		  column index starting from column one.
 Opt. Inputs : 
	None.
 Outputs     : 
	The result of the function is the number of the column specified, or
	zero if no column is found (when passed by name).
 Opt. Outputs: 
	None.
 Keywords    : 
	ERRMSG	  = If defined and passed, then any error messages will be
		    returned to the user in this parameter rather than
		    depending on the MESSAGE routine in IDL.  If no errors are
		    encountered, then a null string is returned.  In order to
		    use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			Result = FXBCOLNUM( ERRMSG=ERRMSG, ... )
			IF ERRMSG NE '' THEN ...

 Calls       : 
	None.
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The binary table file must have been opened with FXBOPEN.

	If COL is passed as a number, rather than as a name, then it must be
	consistent with the number of columns in the table.

 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	None.
 Written     : 
	William Thompson, GSFC, 2 July 1993.
 Modified    : 
	Version 1, William Thompson, GSFC, 2 July 1993.
	Version 2, William Thompson, GSFC, 29 October 1993.
		Added error message for not finding column by name.
	Version 3, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
       Version 4, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
 Version     :
       Version 4, 23 June 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbcolnum.pro)

FXBCREATE

 NAME: 
	FXBCREATE
 Purpose     : 
	Open a new binary table at the end of a FITS file.
 Explanation : 
	Write a binary table extension header to the end of a disk FITS file,
	and leave it open to receive the data.

	The FITS file is opened, and the pointer is positioned just after the
	last 2880 byte record.  Then the binary header is appended.  Calls to
	FXBWRITE will append the binary data to this file, and then FXBFINISH
	will close the file.

 Use         : 
	FXBCREATE, UNIT, FILENAME, HEADER
 Inputs      : 
	FILENAME = Name of FITS file to be opened.
	HEADER	 = String array containing the FITS binary table extension
		   header.
 Opt. Inputs : 
	None.
 Outputs     : 
	UNIT	 = Logical unit number of the opened file.
       EXTENSION= Extension number of newly created extension.
 Opt. Outputs: 
	None.
 Keywords    : 
	ERRMSG	  = If defined and passed, then any error messages will be
		    returned to the user in this parameter rather than
		    depending on the MESSAGE routine in IDL.  If no errors are
		    encountered, then a null string is returned.  In order to
		    use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBCREATE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	FXADDPAR, FXBFINDLUN, FXBPARSE, FXFINDEND
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The primary FITS data unit must already be written to a file.  The
	binary table extension header must already be defined (FXBHMAKE), and
	must match the data that will be written to the file.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Jan 1992, based on WRITEFITS by J. Woffard and W. Landsman.
	W. Thompson, Feb 1992, changed from function to procedure.
	W. Thompson, Feb 1992, removed all references to temporary files.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 July 1993.
		Fixed bug with variable length arrays.
	Version 3, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
	Version 4, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 5, Antony Bird, Southampton, 25 June 1997
		Modified to allow very long tables 
 Version     :
	Version 5, 25 June 1997
	Converted to IDL V5.0   W. Landsman   September 1997
       Added EXTENSION parameter, C. Markwardt 1999 Jul 15
       More efficient zeroing of file, C. Markwardt, 26 Feb 2001
       Recompute header size if updating THEAP keyword B. Roukema April 2010

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbcreate.pro)

FXBDIMEN()

 NAME:
     FXBDIMEN()

 PURPOSE:      
      Returns the dimensions for a column in a FITS binary table.

 Explanation : This procedure returns the dimensions associated with a column
               in a binary table opened for read with the command FXBOPEN.

 Use         : Result = FXBDIMEN(UNIT,COL)

 Inputs      : UNIT    = Logical unit number returned by FXBOPEN routine.
                         Must be a scalar integer.

               COL     = Column in the binary table to read data from, either
                         as a character string containing a column label
                         (TTYPE), or as a numerical column index starting from
                         column one.

 Opt. Inputs : None.

 Outputs     : The result of the function is an array containing the
               dimensions for the specified column in the FITS binary table
               that UNIT points to.

 Opt. Outputs: None.

 Keywords :    ERRMSG  = If defined and passed, then any error messages will
                         be returned to the user in this parameter rather than
                         depending on the MESSAGE routine in IDL.  If no
                         errors are encountered, then a null string is
                         returned.  In order to use this feature, ERRMSG must
                         be defined first, e.g.

                               ERRMSG = ''
                               Result = FXBDIMEN( ERRMSG=ERRMSG, ... )
                               IF ERRMSG NE '' THEN ...

 Calls       : FXBCOLNUM, FXBFINDLUN

 Common      : Uses common block FXBINTABLE--see "fxbintable.pro" for more
               information.

 Restrictions: None.

 Side effects: The dimensions will be returned whether or not the table is
               still open or not.

               If UNIT does not point to a binary table, then 0 is returned.

               If UNIT is an undefined variable, then 0 is returned.

 Category    : Data Handling, I/O, FITS, Generic.

 Prev. Hist. : None.

 Written     : William Thompson, GSFC, 4 March 1994.

 Modified    : Version 1, William Thompson, GSFC, 4 March 1994.
               Version 2, William Thompson, GSFC, 21 June 1994
                       Added ERRMSG keyword.
               Version 3, William Thompson, GSFC, 23 June 1994
                       Modified so that ERRMSG is not touched if not defined.

 Version     : Version 3, 23 June 1994
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbdimen.pro)

FXBFIND

 NAME: 
	FXBFIND
 Purpose     : 
	Find column keywords in a FITS binary table header.
 Explanation : 
	Finds the value of a column keyword for all the columns in the binary
	table for which it is set.  For example,

		FXBFIND, UNIT, 'TTYPE', COLUMNS, VALUES, N_FOUND

	Would find all instances of the keywords TTYPE1, TTYPE2, etc.  The
	array COLUMNS would contain the column numbers for which a TTYPEn
	keyword was found, and VALUES would contain the values.  N_FOUND would
	contain the total number of instances found.

 Use         : 
	FXBFIND, [UNIT or HEADER], KEYWORD, COLUMNS, VALUES, N_FOUND
		[, DEFAULT ]
 Inputs      : 
	Either UNIT or HEADER must be passed.

	UNIT	= Logical unit number of file opened by FXBOPEN.
	HEADER	= FITS binary table header.
	KEYWORD	= Prefix to a series of FITS binary table column keywords.  The
		  keywords to be searched for are formed by combining this
		  prefix with the numbers 1 through the value of TFIELDS in the
		  header.
 Opt. Inputs : 
	DEFAULT	= Default value to use for any column keywords that aren't
		  found.  If passed, then COLUMNS and VALUES will contain
		  entries for every column.  Otherwise, COLUMNS and VALUES only
		  contain entries for columns where values were found.
 Outputs     : 
	COLUMNS	= Array containing the column numbers for which values of the
		  requested keyword series were found.
	VALUES	= Array containing the found values.
	N_FOUND	= Number of values found.  The value of this parameter is
		  unaffected by whether or not DEFAULT is passed.
 Opt. Outputs: 
	None.
 Output Keywords    : 
      COMMENTS = Comments associated with each keyword, if any
 Calls       : 
	FXBFINDLUN, FXPAR
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	If UNIT is passed, then the file must have been opened with FXBOPEN.
	If HEADER is passed, then it must be a legal FITS binary table header.

	The type of DEFAULT must be consistent with the values of the requested
	keywords, i.e. both most be either of string or numerical type.

	The KEYWORD prefix must not have more than five characters to leave
	room for the three digits allowed for the column numbers.

 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Feb. 1992.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
       Vectorized implementation improves performance, CM 18 Nov 1999
       Added COMMENTS keyword CM Nov 2003
       Remove use of obsolete !ERR system variable W. Landsman April 2010
       Fix error introduced April 2010  W. Landsman
 Version     : 
	Version 3, April 2010.

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbfind.pro)

FXBFINDLUN()

 NAME: 
	FXBFINDLUN()
 Purpose     : 
	Find logical unit number UNIT in FXBINTABLE common block.
 Explanation : 
	Finds the proper index to use for getting information about the logical
	unit number UNIT in the arrays stored in the FXBINTABLE common block.
	Called from FXBCREATE and FXBOPEN.
 Use         : 
	Result = FXBFINDLUN( UNIT )
 Inputs      : 
	UNIT	= Logical unit number.
 Opt. Inputs : 
	None.
 Outputs     : 
	The result of the function is an index into the FXBINTABLE common
	block.
 Opt. Outputs: 
	None.
 Keywords    : 
	None.
 Calls       : 
	None.
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	None.
 Side effects: 
	If UNIT is not found in the common block, then it is added to the
	common block.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Feb. 1992.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 July 1993.
		Added DHEAP variable to fix bug with variable length arrays.
	Version 3, Michael Schubnell, University of Michigan, 22 May 1996
		Change N_DIMS from short to long integer.
 Version     : 
	Version 3, 22 May 1996
	Converted to IDL V5.0   W. Landsman   September 1997
       Make NAXIS1, NAXIS2, HEAP, DHEAP, BYTOFF 64-bit integers to deal with large files,
         E. Hivon Mar 2008

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbfindlun.pro)

FXBFINISH

 NAME: 
	FXBFINISH
 Purpose     : 
	Close a FITS binary table extension file opened for write.
 Explanation : 
	Closes a FITS binary table extension file that had been opened for
	write by FXBCREATE.
 Use         : 
	FXBFINISH, UNIT
 Inputs      : 
	UNIT	= Logical unit number of the file.
 Opt. Inputs : 
	None.
 Outputs     : 
	None.
 Opt. Outputs: 
	None.
 Keywords    : 
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBFINISH, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	None.
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The file must have been opened with FXBCREATE, and written with
	FXBWRITE.
 Side effects: 
	Any bytes needed to pad the file out to an integral multiple of 2880
	bytes are written out to the file.  Then, the file is closed.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Jan 1992.
	W. Thompson, Feb 1992, modified to support variable length arrays.
	W. Thompson, Feb 1992, removed all references to temporary files.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 July 1993.
		Fixed bug with variable length arrays.
	Version 3, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
       Version 4, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
 Version     :
       Version 4, 23 June 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbfinish.pro)

FXBGROW

 NAME: 
        FXBGROW
 PURPOSE     : 
       Increase the number of rows in a binary table.
 EXPLANATION : 
       Call FXBGROW to increase the size of an already-existing FITS
       binary table.  The number of rows increases to NROWS; however
       the table cannot shrink by this operation.  This procedure is
       useful when a table with an unknown number of rows must be
       created.  The caller would then call FXBCREATE to construct a
       table of some base size, and follow with calls to FXBGROW to
       lengthen the table as needed.  The extension being enlarged
       need not be the last extension in the file.  If subsequent
       extensions exist in the file, they will be shifted properly.

 CALLING SEQUENCE :
       FXBGROW, UNIT, HEADER, NROWS[, ERRMSG= , NOZERO= , BUFFERSIZE= ]

 INPUT PARAMETERS :
       UNIT     = Logical unit number of an already-opened file.
       HEADER   = String array containing the FITS binary table extension
                  header.  The header is modified in place.
       NROWS    = New number of rows, always more than the previous
                  number.

 OPTIONAL INPUT KEYWORDS:
       NOZERO   = when set, FXBGROW will not zero-pad the new data if
                  it doesn't have to.
       ERRMSG    = If defined and passed, then any error messages will be
                   returned to the user in this parameter rather than
                   depending on the MESSAGE routine in IDL.  If no errors are
                   encountered, then a null string is returned.  In order to
                   use this feature, ERRMSG must be defined first, e.g.

                       ERRMSG = ''
                       FXBGROW, ERRMSG=ERRMSG, ...
                       IF ERRMSG NE '' THEN ...
       BUFFERSIZE = Size in bytes for intermediate data transfers
                    (default 32768)

 Calls       : 
       FXADDPAR, FXHREAD, BLKSHIFT
 Common      : 
       Uses common block FXBINTABLE--see "fxbintable.pro" for more
       information.
 Restrictions: 
       The file must be open with write permission.

       The binary table extension in question must already by written
       to the file (using FXBCREATE).

       A table can never shrink via this operation.

 SIDE EFFECTS: 
       The FITS file will grow in size, and heap areas are
       preserved by moving them to the end of the file.

       The header is modified to reflect the new number of rows.
 CATEGORY    : 
       Data Handling, I/O, FITS, Generic.
       Initially written, C. Markwardt, GSFC, Nov 1998
       Added ability to enlarge arbitrary extensions and tables with
         variable sized rows, not just the last extension in a file,
         CM, April 2000
       Fix bug in the zeroing of the output file, C. Markwardt, April 2005

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbgrow.pro)

FXBHEADER()

 NAME: 
       FXBHEADER()

 PURPOSE: 
       Returns the header of an open FITS binary table.

 EXPLANATION:
      This procedure returns the FITS extension header of a FITS
         binary table opened for read with the command FXBOPEN.

 Use         : Result = FXBHEADER(UNIT)

 Inputs      : UNIT    = Logical unit number returned by FXBOPEN routine.
                         Must be a scalar integer.

 Opt. Inputs : None.

 Outputs     : The result of the function is a string array containing the
               header for the FITS binary table that UNIT points to.

 Opt. Outputs: None.

 Keywords    : None.

 Calls       : FXBFINDLUN

 Common      : Uses common block FXBINTABLE--see "fxbintable.pro" for more
               information.

 Restrictions: None.

 Side effects: The string array returned always has as many elements as the
               largest header read by FXBOPEN.  Any extra elements beyond the
               true header are blank or null strings.

               The header will be returned whether or not the table is still
               open or not.

               If UNIT does not point to a binary table, then a string array
               of nulls is returned.

               If UNIT is an undefined variable, then the null string is
               returned.

 Category    : Data Handling, I/O, FITS, Generic.

 Prev. Hist. : None.

 Written     : William Thompson, GSFC, 1 July 1993.

 Modified    : Version 1, William Thompson, GSFC, 1 July 1993.

 Version     : Version 1, 1 July 1993.
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbheader.pro)

FXBHELP

 NAME: 
	FXBHELP
 Purpose     : 
	Prints short description of columns in a FITS binary table.
 Explanation : 
	Prints a short description of the columns in a FITS binary table to the
	terminal screen.
 Use         : 
	FXBHELP, UNIT
 Inputs      : 
	UNIT	= Logical unit number of file opened by FXBOPEN.
 Opt. Inputs : 
	None.
 Outputs     : 
	None.
 Opt. Outputs: 
	None.
 Keywords    : 
	None.
 Calls       : 
	FXBFIND, FXBFINDLUN, FXPAR
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The file must have been opened with FXBOPEN.
 Side effects: 
	Certain fields may be truncated in the display.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Feb. 1992, from TBHELP by W. Landsman.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 12 May 1993.
		Modified to not write to a logical unit number assigned to the
		terminal.  This makes it compatible with IDL for Windows.
       Version 3, Wayne Landsman GSFC April 2010
                Remove use of obsolete !ERR system variable
 Version     : 
	Version 3, April 2010.

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbhelp.pro)

FXBHMAKE

 NAME: 
	FXBHMAKE
 Purpose     : 
	Create basic FITS binary table extension (BINTABLE) header.
 Explanation : 
	Creates a basic header array with all the required keywords, but with
	none of the table columns defined.  This defines a basic structure
	which can then be added to or modified by other routines.
 Use         : 
	FXBHMAKE, HEADER, NROWS  [, EXTNAME  [, COMMENT ]]
 Inputs      : 
	NROWS	= Number of rows in the binary table.
 Opt. Inputs : 
	EXTNAME	= If passed, then the EXTNAME record is added with this value.
	COMMENT = Comment to go along with EXTNAME.
 Outputs     : 
	HEADER = String array containing FITS extension header.
 Opt. Outputs: 
	None.
 Keywords    : 
	INITIALIZE = If set, then the header is completely initialized, and any
		     previous entries are lost.
	DATE	   = If set, then the DATE keyword is added to the header.
	EXTVER	   = Extension version number (integer).
	EXTLEVEL   = Extension level number (integer).
	ERRMSG	   = If defined and passed, then any error messages will be
		     returned to the user in this parameter rather than
		     depending on the MESSAGE routine in IDL.  If no errors are
		     encountered, then a null string is returned.  In order to
		     use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBHMAKE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	GET_DATE, FXADDPAR, FXHCLEAN
 Common      : 
	None.
 Restrictions: 
	Warning:  No checking is done of any of the parameters.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Jan 1992.
	William Thompson, Sep 1992, added EXTVER and EXTLEVEL keywords.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
 Version     :
       Version 3, 23 June 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbhmake.pro)

FXBINTABLE

 NAME: 
	FXBINTABLE
 Purpose     : 
	Common block FXBINTABLE used by "FXB" routines.
 Explanation : 
	This is not an IDL routine as such, but contains the definition of the
	common block FXBINTABLE for inclusion into other routines.  By defining
	the common block in one place, the problem of conflicting definitions
	is avoided.

	This file is included into routines that need this common block with
	the single line (left justified)

				  @fxbintable

	FXBINTABLE contains the following arrays:

		LUN	= An array of logical unit numbers of currently (or
			  previously) opened binary table files.
		STATE	= Array containing the state of the FITS files
			  associated with the logical unit numbers, where
			  0=closed, 1=open for read, and 2=open for write.
		HEAD	= FITS binary table headers.
		MHEADER	= Array containing the positions of the first data byte
			  of the header for each file referenced by array LUN.
		NHEADER	= Array containing the positions of the first data byte
			  after the header for each file referenced by array
			  LUN.
		NAXIS1	= Values of NAXIS1 from the binary table headers.
		NAXIS2	= Values of NAXIS2 from the binary table headers.
		TFIELDS	= Values of TFIELDS from the binary table headers.
		HEAP	= The start of the first byte of the heap area
			  for variable length arrays.
		DHEAP	= The start of the first byte of the next variable
			  length array, if writing.
		BYTOFF	= Byte offset from the beginning of the row for each
			  column in the binary table headers.
		TTYPE	= Values of TTYPE for each column in the binary table
			  headers.
		FORMAT	= Character code formats of the various columns.
		IDLTYPE	= IDL type code for each column in the binary table
			  headers.
		N_ELEM	= Number of elements for each column in the binary
			  table headers.
		TSCAL	= Scale factors for the individual columns.
		TZERO	= Zero offsets for the individual columns.
		MAXVAL	= For variable length arrays, contains the maximum
			  number of elements for each column in the binary
			  table headers.
		N_DIMS	= Number of dimensions, and array of dimensions for
			  each column of type string in the binary table
			  headers.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Feb 1992.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 July 1993.
		Added DHEAP variable to fix bug with variable length arrays.
 Version     : 
	Version 2, 21 July 1993.

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbintable.pro)

FXBISOPEN()

 NAME: 
       FXBISOPEN()

 PURPOSE: 
       Returns true if UNIT points to an open FITS binary table.

 Explanation : This procedure checks to see if the logical unit number given
               by the variable UNIT corresponds to a FITS binary table opened
               for read with the command FXBOPEN, and which has not yet been
               closed with FXBCLOSE.

 Use         : Result = FXBISOPEN(UNIT)

               If FXBISOPEN(UNIT) THEN ...

 Inputs      : UNIT    = Logical unit number returned by FXBOPEN routine.
                         Must be a scalar integer.

 Opt. Inputs : None.

 Outputs     : The result of the function is either True (1) or False (0),
               depending on whether UNIT points to an open binary table or
               not.

 Opt. Outputs: None.

 Keywords    : None.

 Calls       : FXBFINDLUN

 Common      : Uses common block FXBINTABLE--see "fxbintable.pro" for more
               information.

 Restrictions: None.

 Side effects: If UNIT is an undefined variable, then False (0) is returned.

               If UNIT points to a FITS binary table file that is opened for
               write, then False (0) is returned.

 Category    : Data Handling, I/O, FITS, Generic.

 Prev. Hist. : None.

 Written     : William Thompson, GSFC, 1 July 1993.

 Modified    : Version 1, William Thompson, GSFC, 1 July 1993.

 Version     : Version 1, 1 July 1993.
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbisopen.pro)

FXBOPEN

 NAME: 
	FXBOPEN
 Purpose     : 
	Open binary table extension in a disk FITS file for reading or updating
 Explanation : 
	Opens a binary table extension in a disk FITS file for reading.  The
	columns are then read using FXBREAD, and the file is closed when done
	with FXBCLOSE.
 Use         : 
	FXBOPEN, UNIT, FILENAME, EXTENSION  [, HEADER ]
 Inputs      : 
       FILENAME  = Name of FITS file to be opened.  Optional
                   extension *number* may be specified, in either of
                   the following formats (using the FTOOLS
                   convention): FILENAME[EXT] or FILENAME+EXT, where
                   EXT is 1 or higher.  Such an extension
                   specification takes priority over EXTENSION.
                
	EXTENSION = Either the number of the FITS extension, starting with the
		    first extension after the primary data unit being one; or a
		    character string containing the value of EXTNAME to search
		    for.
 Opt. Inputs : 
	None.
 Outputs     : 
	UNIT	  = Logical unit number of the opened file.
 Opt. Outputs: 
	HEADER	  = String array containing the FITS binary table extension
		    header.
 Keywords    : 
	NO_TDIM	  = If set, then any TDIMn keywords found in the header are
		    ignored.

       ACCESS    = A scalar string describing access privileges as
                   one of READ ('R') or UPDATE ('RW').
                   DEFAULT: 'R'

       REOPEN    = If set, UNIT must be an already-opened file unit.
                   FXBOPEN will treat the file as a FITS file.

	ERRMSG	  = If defined and passed, then any error messages will be
		    returned to the user in this parameter rather than
		    depending on the MESSAGE routine in IDL.  If no errors are
		    encountered, then a null string is returned.  In order to
		    use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBOPEN, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	FXBFINDLUN, FXBPARSE, FXHREAD, FXPAR
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The file must be a valid FITS file.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Feb 1992, based on READFITS by J. Woffard and W. Landsman.
	W. Thompson, Feb 1992, changed from function to procedure.
	W. Thompson, June 1992, fixed up error handling.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 27 May 1994
		Added ERRMSG keyword.
	Version 3, William Thompson, GSFC, 21 June 1994
		Extended ERRMSG to call to FXBPARSE
       Version 4, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
       Version 4, 23 June 1994

 Added ACCESS, REOPEN keywords, and FXFILTER package, CM 1999 Feb 03
 Added FILENAME[EXT] and FILENAME+EXT extension parsing, CM 1999 Jun 28
 Some general tidying, CM 1999 Nov 18
       Allow for possible 64bit integer number of bytes W. Landsman Nov 2007
       Make Ndata a 64bit integer to deal with larger files, E. Hivon, Mar 2008

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbopen.pro)

FXBPARSE

 NAME: 
	FXBPARSE
 Purpose     : 
	Parse the binary table extension header.
 Explanation : 
	Parses the binary table extension header, and store the information
	about the format of the binary table in the FXBINTABLE common
	block--called from FXBCREATE and FXBOPEN.
 Use         : 
	FXBPARSE, ILUN, UNIT, HEADER
 Inputs      : 
	ILUN	= Index into the arrays in the FXBINTABLE common block.
	HEADER	= FITS binary table extension header.
 Opt. Inputs : 
	None.
 Outputs     : 
	None.
 Opt. Outputs: 
	None.
 Keywords    : 
	NO_TDIM	  = If set, then any TDIMn keywords found in the header are
		    ignored.
	ERRMSG	  = If defined and passed, then any error messages will be
		    returned to the user in this parameter rather than
		    depending on the MESSAGE routine in IDL.  If no errors are
		    encountered, then a null string is returned.  In order to
		    use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBPARSE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	FXBFIND, FXBTDIM, FXBTFORM, FXPAR
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	None.
 Side effects: 
	Any TDIMn keywords found for bit arrays (format 'X') are ignored, since
	the dimensions would refer to bits, not bytes.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Feb. 1992.
	William Thompson, Jan. 1993, modified for renamed FXBTFORM and FXBTDIM.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 4, Michael Schubnell, University of Michigan, 22 May 1996
		Change N_DIMS from short to long integer.
	Version 5, W. Landsman, GSFC, 12 Aug 1997
		Use double complex datatype, if needed
	Version 6, W. Landsman GSFC 30 Aug 1997
       Optimized FXPAR; call FXBFIND for speed, CM 1999 Nov 18
       Modify DHEAP(ILUN) when opening table now, CM 2000 Feb 22
       Default the TZERO/TSCAL tables to double instead of single
         precision floating point, CM 2003 Nov 23
       Make NAXIS1 and NAXIS2 64-bit integers to deal with large files,
         E. Hivon Mar 2008
       Remove use of Obsolete !ERR system variable
  Version 
       Version 8   April 2010

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbparse.pro)

FXBREAD

 NAME: 
	FXBREAD
 Purpose     : 
	Read a data array from a disk FITS binary table file.
 Explanation : 
	Each call to FXBREAD will read the data from one column and one row
	from the FITS data file, which should already have been opened by
	FXBOPEN.  One needs to call this routine for every column and every row
	in the binary table.  FXBCLOSE will then close the FITS data file.
 Use         : 
	FXBREAD, UNIT, DATA, COL  [, ROW ]
 Inputs      : 
	UNIT	= Logical unit number corresponding to the file containing the
		  binary table.
	COL	= Column in the binary table to read data from, either as a
		  character string containing a column label (TTYPE), or as a
		  numerical column index starting from column one.
 Opt. Inputs : 
	ROW	= Either row number in the binary table to read data from,
		  starting from row one, or a two element array containing a
		  range of row numbers to read.  If not passed, then the entire
		  column is read in.

		  Row must be passed for variable length arrays.

 Outputs     : 
	DATA	= IDL data array to be read from the file.
 Opt. Outputs: 
	None.
 Keywords    : 
	NOSCALE	= If set, then the output data will not be scaled using the
		  optional TSCAL and TZERO keywords in the FITS header.
		  Default is to scale.
       NOIEEE  = If set, then the output data is not byte-swapped to 
                 machine order.  NOIEEE implies NOSCALE.
                 Default is to perform the byte-swap.
	VIRTUAL	= If set, and COL is passed as a name rather than a number,
		  then if the program can't find a column with that name, it
		  will then look for a keyword with that name in the header.
		  Such a keyword would then act as a "virtual column", with the
		  same value for every row.
	DIMENSIONS = Vector array containing the dimensions to be used to read
		  in the data.  Bypasses any dimensioning information stored in
		  the header.  Ignored for bit arrays.  If the data type is
		  double-precision complex, then an extra dimension of 2 is
		  prepended to the dimensions passed by the user.
	NANVALUE= Value signalling data dropout.  All points corresponding to
		  IEEE NaN (not-a-number) are converted to this number.
		  Ignored unless DATA is of type float, double-precision or
		  complex.
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBREAD, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	FXPAR, WHERE_NEGZERO, WHERENAN
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The binary table file must have been opened with FXBOPEN.

	The data must be consistent with the column definition in the binary
	table header.

	The row number must be consistent with the number of rows stored in the
	binary table header.

	The number of elements implied by the dimensions keyword must not
	exceed the number of elements stored in the file.

 Side effects: 
	If the DIMENSIONS keyword is used, then the number of data points read
	in may be less than the number of points stored in the table.

	If there are no elements to read in (the number of elements is zero),
	then the program sets !ERR to -1, and DATA is unmodified.

 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Jan 1992.
	W. Thompson, Feb 1992, modified to support variable length arrays.
	W. Thompson, Jun 1992, modified way that row ranges are read in.  No
			       longer works reiteratively.
	W. Thompson, Jun 1992, fixed bug where NANVALUE would be modified by
			       TSCAL and TZERO keywords.
	W. Thompson, Jun 1992, fixed bug when reading character strings.
			       Treats dimensions better when reading multiple
			       rows.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 30 June 1993.
		Added overwrite keyword to REFORM call to speed up.
	Version 3, William Thompson, GSFC, 21 July 1993.
		Fixed bug with variable length arrays.
	Version 4, William Thompson, GSFC, 29 October 1993.
		Added error message for not finding column by name.
	Version 5, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
       Version 6, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 7, William Thompson, GSFC, 29 December 1994
		Fixed bug where single element dimensions were lost.
	Version 8, William Thompson, GSFC, 20 March 1995
		Fixed bug introduced in version 7.
	Version 9, Wayne Landsman, GSFC, 3 July 1996
		Fixed bug involving use of virtual keyword.
	Version 10, William Thompson, GSFC, 31-Jan-1997
		Added call to WHERE_NEGZERO.
	Version 11, Wayne Landsman, GSFC, 12 Aug, 1997
		Use IDL dcomplex datatype if needed
	Version 12, Wayne Landmsan, GSFC, 20 Feb, 1998
		Remove call to WHERE_NEGZERO (now part of IEEE_TO_HOST)
	Version 13, 18 Nov 1999, CM, Add NOIEEE keyword
	Version 14, 21 Aug 2000, William Thompson, GSFC
		Catch I/O errors
       Version 15, W. Landsman GSFC 10 Dec 2009
                Fix Dimension keyword, remove  IEEE_TO_HOST
 Version     :
       Version 15, 10 Dec 2009

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbread.pro)

FXBREADM

 NAME:
       FXBREADM
 PURPOSE: 
       Read multiple columns/rows from a disk FITS binary table file.
 EXPLANATION : 
       A call to FXBREADM will read data from multiple rows and
       multiple columns in a single procedure call.  Up to forty-nine
       columns may be read in a single pass; the number of rows is
       limited essentially by available memory.  The file should have
       already been opened with FXBOPEN.  FXBREADM optimizes reading
       multiple columns by first reading a large chunk of data from
       the FITS file directly, and then slicing the data into columns
       within memory.  FXBREADM can read variable-length arrays (see
       below).

       The number of columns is limited to 49 if data are passed by
       positional argument.  However, this limitation can be overcome
       by having FXBREADM return the data in an array of pointers.
       The user should set the PASS_METHOD keyword to 'POINTER', and an 
       array of pointers to the data will be returned in the POINTERS keyword.
       The  user is responsible for freeing the pointers; however,
       FXBREADM will reuse any pointers  passed into the procedure, and 
       hence any pointed-to data will be destroyed.

       FXBREADM can also read variable-length columns from FITS
       binary tables.  Since such data is not of a fixed size, it is
       returned as a structure.  The structure has the following
       elements:

              VARICOL:    ;; Flag: variable length column (= 1)
              N_ELEMENTS: ;; Total number of elements returned
              TYPE:       ;; IDL data type code (integer)
              N_ROWS:     ;; Number of rows read from table (integer)
              INDICES:    ;; Indices of each row's data (integer array)
              DATA:       ;; Raw data elements (variable type array)

       In order to gain access to the Ith row's data, one should
       examine DATA(INDICES(I):INDICES(I+1)-1), which is similar in
       construct to the REVERSE_INDICES keyword of the HISTOGRAM
       function.

 CALLING SEQUENCE: 
       FXBREADM, UNIT, COL, DATA1, [ DATA2, ... DATA48, ROW=, BUFFERSIZE = ]
           /NOIEEE, /NOSCALE, /VIRTUAL, NANVALUE=, PASS_METHOD = POINTERS=, 
           ERRMSG = , WARNMSG = , STATUS = , /DEFAULT_FLOAT]

 INPUT PARAMETERS : 
       UNIT    = Logical unit number corresponding to the file containing the
                 binary table.
       COL     = An array of columns in the binary table to read data
                 from, either as character strings containing column
                 labels (TTYPE), or as numerical column indices
                 starting from column one.
 Outputs     : 
       DATA1, DATA2...DATA48 = A named variable to accept the data values, one
                 for each column.  The columns are stored in order of the
                 list in COL.  If the read operation fails for a
                 particular column, then the corresponding output Dn
                 variable is not altered.  See the STATUS keyword.
                 Ignored if PASS_METHOD is 'POINTER'.

 OPTIONAL INPUT KEYWORDS: 
       ROW     = Either row number in the binary table to read data from,
                 starting from row one, or a two element array containing a
                 range of row numbers to read.  If not passed, then the entire
                 column is read in.
       /DEFAULT_FLOAT = If set, then scaling with TSCAL/TZERO is done with
                 floating point rather than double precision.
       /NOIEEE = If set, then then IEEE floating point data will not
                be converted to the host floating point format (and
                this by definition implies NOSCALE).  The user is
                responsible for their own floating point conversion.
       /NOSCALE = If set, then the output data will not be scaled using the
                 optional TSCAL and TZERO keywords in the FITS header.
                 Default is to scale.
       VIRTUAL = If set, and COL is passed as a name rather than a number,
                 then if the program can't find a column with that name, it
                 will then look for a keyword with that name in the header.
                 Such a keyword would then act as a "virtual column", with the
                 same value for every row.
       DIMENSIONS = FXBREADM ignores this keyword.  It is here for
	          compatibility only.
       NANVALUE= Value signalling data dropout.  All points corresponding to
                 IEEE NaN (not-a-number) are converted to this number.
                 Ignored unless DATA is of type float, double-precision or
                 complex.
       PASS_METHOD = A scalar string indicating method of passing
                 data from FXBREADM.  Either 'ARGUMENT' (indicating
                 pass by positional argument), or 'POINTER' (indicating
                 passing an array of pointers by the POINTERS
                 keyword).
                 Default: 'ARGUMENT'
       POINTERS = If PASS_METHOD is 'POINTER' then an array of IDL
                 pointers is returned in this keyword, one for each
                 requested column.    Any pointers passed into FXBREADM will 
                 have their pointed-to data destroyed.  Ultimately the
                 user is responsible for deallocating pointers. 
       BUFFERSIZE = Raw data are transferred from the file in chunks
                 to conserve memory.  This is the size in bytes of
                 each chunk.  If a value of zero is given, then all
                 of the data are transferred in one pass.  Default is
                 32768 (32 kB).
 OPTIONAL OUTPUT KEYWORDS:
       ERRMSG  = If defined and passed, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.  In order to
                 use this feature, ERRMSG must be defined first, e.g.

                       ERRMSG = ''
                       FXBREAD, ERRMSG=ERRMSG, ...
                       IF ERRMSG NE '' THEN ...
       WARNMSG = Messages which are considered to be non-fatal
                 "warnings" are returned in this output string.
                 Note that if some but not all columns are
                 unreadable, this is considered to be non-fatal.
       STATUS  = An output array containing the status for each
                 column read, 1 meaning success and 0 meaning failure.

 Calls       : 
       IEEE_TO_HOST, FXPAR(), WHERENAN()
 Common      : 
       Uses common block FXBINTABLE--see "fxbintable.pro" for more
       information.
 Restrictions: 
       The binary table file must have been opened with FXBOPEN.

       The data must be consistent with the column definition in the binary
       table header.

       The row number must be consistent with the number of rows stored in the
       binary table header.

       Generaly speaking, FXBREADM will be faster than iterative
       calls to FXBREAD when (a) a large number of columns is to be
       read or (b) the size in bytes of each cell is small, so that
       the overhead of the FOR loop in FXBREAD becomes significant.

 SIDE EFFECTS: 
       If there are no elements to read in (the number of elements is zero),
       then the program sets !ERR to -1, and DATA is unmodified.

 Category    : 
       Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
       C. Markwardt, based in concept on FXBREAD version 12 from
                              IDLASTRO, but with significant and
                              major changes to accomodate the
                              multiple row/column technique.  Mostly
                              the parameter checking and general data
                              flow remain.
       C. Markwardt, updated to read variable length arrays, and to
                              pass columns by handle or pointer.
                              20 Jun 2001
       C. Markwardt, try to conserve memory when creating the arrays
                              13 Oct 2001
   Handle case of GE 50 columns, C. Markwardt, 18 Apr 2002
   Handle case where TSCAL/TZERO changes type of column,
       C. Markwardt, 23 Feb 2003
   Fix bug in handling of FOUND and numeric columns, 
       C. Markwardt 12 May 2003
   Removed pre-V5.0 HANDLE options  W. Landsman July 2004
   Fix bug when HANDLE options were removed, July 2004
   Handle special cases of TSCAL/TZERO which emulate unsigned
      integers, Oct 2003
   Add DEFAULT_FLOAT keyword to select float values instead of double
      for TSCAL'ed, June 2004
   Read 64bit integer columns, E. Hivon, Mar 2008
   Add support for columns with TNULLn keywords, C. Markwardt, Apr 2010
   Add support for files larger than 2 GB, C. Markwardt, 2012-04-17

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbreadm.pro)

FXBSTATE()

 NAME: 
      FXBSTATE()

 PURPOSE:
       Returns the state of a FITS binary table.

 Explanation : This procedure returns the state of a FITS binary table that
               was either opened for read with the command FXBOPEN, or for
               write with the command FXBCREATE.

 Use         : Result = FXBSTATE(UNIT)

 Inputs      : UNIT    = Logical unit number returned by FXBOPEN routine.
                         Must be a scalar integer.

 Opt. Inputs : None.

 Outputs     : The result of the function is the state of the FITS binary
               table that UNIT points to.  This can be one of three values:

                       0 = Closed
                       1 = Open for read
                       2 = Open for write

 Opt. Outputs: None.

 Keywords    : None.

 Calls       : FXBFINDLUN

 Common      : Uses common block FXBINTABLE--see "fxbintable.pro" for more
               information.

 Restrictions: None.

 Side effects: If UNIT is an undefined variable, then 0 (closed) is returned.

 Category    : Data Handling, I/O, FITS, Generic.

 Prev. Hist. : None.

 Written     : William Thompson, GSFC, 1 July 1993.

 Modified    : Version 1, William Thompson, GSFC, 1 July 1993.

 Version     : Version 1, 1 July 1993.
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbstate.pro)

FXBTDIM()

 NAME: 
	FXBTDIM()
 Purpose     : 
	Parse TDIM-like kwywords.
 Explanation : 
	Parses the value of a TDIM-like keyword (e.g. TDIMnnn, TDESC, etc.) to
	return the separate elements contained within.
 Use         : 
	Result = FXBTDIM( TDIM_KEYWORD )
 Inputs      : 
	TDIM_KEYWORD	= The value of a TDIM-like keyword.  Must be a
			  character string of the form "(value1,value2,...)".
			  If the parentheses characters are missing, then the
			  string is simply returned as is, without any further
			  processing.
 Opt. Inputs : 
	None.
 Outputs     : 
	The result of the function is a character string array containing the
	values contained within the keyword parameter.  If a numerical result
	is desired, then simply call, e.g.

		Result = FIX( FXBTDIM( TDIM_KEYWORD ))

 Opt. Outputs: 
	None.
 Keywords    : 
	None.
 Calls       : 
	GETTOK
 Common      : 
	None.
 Restrictions: 
	The input parameter must have the proper format.  The separate values
	must not contain the comma character.  TDIM_KEYWORD must not be an
	array.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Jan. 1992.
	William Thompson, Jan. 1993, renamed to be compatible with DOS
		limitations.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
 Version     : 
	Version 1, 12 April 1993.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbtdim.pro)

FXBTFORM

 NAME: 
	FXBTFORM
 PURPOSE     : 
	Returns information about FITS binary table columns.
 EXPLANATION : 
	Procedure to return information about the format of the various columns
	in a FITS binary table.
 Use         : 
	FXBTFORM,HEADER,TBCOL,IDLTYPE,FORMAT,NUMVAL,MAXVAL
 Inputs      : 
	HEADER	= Fits binary table header.
 Opt. Inputs : 
	None.
 Outputs     : 
	TBCOL	= Array of starting column positions in bytes.
	IDLTYPE	= IDL data types of columns.
	FORMAT	= Character code defining the data types of the columns.
	NUMVAL	= Number of elements of the data arrays in the columns.
	MAXVAL	= Maximum number of elements for columns containing variable
		  length arrays, or zero otherwise.
 Opt. Outputs: 
	None.
 Keywords    : 
	ERRMSG	  = If defined and passed, then any error messages will be
		    returned to the user in this parameter rather than
		    depending on the MESSAGE routine in IDL.  If no errors are
		    encountered, then a null string is returned.  In order to
		    use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBTFORM, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	FXPAR
 Common      : 
	None.
 Restrictions: 
	None.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Feb. 1992, from TBINFO by D. Lindler.
	W. Thompson, Jan. 1993, renamed to be compatible with DOS limitations.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 4, William Thompson, GSFC, 9 April 1997
		Modified so that variable length arrays can be read, even if
		the maximum array size is not in the header.
	Version 5  Wayne Landsman, GSFC, August 1997
		Recognize double complex array type if since IDL version 4.0
       Version 6  Optimized FXPAR call, CM 1999 Nov 18
       Version 7: Wayne Landsman, GSFC Feb 2006
               Added support for 64bit integer K format
 Version:
       Version 8: Wayne Landsman GSFC Apr 2010
               Remove use of obsolete !ERR variable

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbtform.pro)

FXBWRITE

 NAME: 
	FXBWRITE
 Purpose     : 
	Write a binary data array to a disk FITS binary table file.
 Explanation : 
	Each call to FXBWRITE will write to the data file, which should already
	have been created and opened by FXBCREATE.  One needs to call this
	routine for every column and every row in the binary table.  FXBFINISH
	will then close the file.
 Use         : 
	FXBWRITE, UNIT, DATA, COL, ROW
 Inputs      : 
	UNIT	= Logical unit number corresponding to the file containing the
		  binary table.
	DATA	= IDL data array to be written to the file.
	COL	= Column in the binary table to place data in, starting from
		  column one.
	ROW	= Row in the binary table to place data in, starting from row
		  one.
 Opt. Inputs : 
	None.
 Outputs     : 
	None.
 Opt. Outputs: 
	None.
 Keywords    : 
	BIT	= Number of bits in bit mask arrays (type "X").  Only used if
		  the column is of variable size.
	NANVALUE= Value signalling data dropout.  All points corresponding to
		  this value are set to be IEEE NaN (not-a-number).  Ignored
		  unless DATA is of type float, double-precision or complex.
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBWRITE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	HOST_TO_IEEE
 Common      : 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 Restrictions: 
	The binary table file must have been opened with FXBCREATE.

	The data must be consistent with the column definition in the binary
	table header.

	The row number must be consistent with the number of rows stored in the
	binary table header.

 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Jan 1992, based on WRITEFITS by J. Woffard and W. Landsman.
	W. Thompson, Feb 1992, modified to support variable length arrays.
	W. Thompson, Feb 1992, removed all references to temporary files.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 July 1993.
		Fixed bug with variable length arrays.
	Version 3, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
       Version 4, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 5, Wayne Landsman, GSFC, 12 Aug 1997
		Recognize IDL double complex data type
 Version     :
       Version 5, 12 August 1997
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbwrite.pro)

FXBWRITM

 NAME: 
	FXBWRITM
 PURPOSE: 
       Write multiple columns/rows to a disk FITS binary table file.
 EXPLANATION : 
       A call to FXBWRITM will write multiple rows and multiple
       columns to a binary table in a single procedure call.  Up to
       fifty columns may be read in a single pass.  The file should
       have already been opened with FXBOPEN (with write access) or
       FXBCREATE.  FXBWRITM optimizes writing multiple columns by
       first writing a large chunk of data to the FITS file all at
       once.  FXBWRITM cannot write variable-length arrays; use
       FXBWRITE instead.

       The number of columns is limited to 50 if data are passed by
       positional argument.  However, this limitation can be overcome
       by passing pointers to FXBWRITM.  The user should set the PASS_METHOD 
       keyword to 'POINTER'  as appropriate, and  an array of pointers to 
       the data in the POINTERS keyword.  The user is responsible for freeing 
        the pointers.

 CALLING SEQUENCE: 
	FXBWRITM, UNIT, COL, D0, D1, D2, ..., [ ROW= , PASS_METHOD, NANVALUE=
                               POINTERS=,  BUFFERSIZE= ]
    
 INPUT PARAMETERS: 
	UNIT	= Logical unit number corresponding to the file containing the
		  binary table.
	D0,..D49= An IDL data array to be written to the file, one for
                 each column.      These parameters will be igonred if data
                 is passed through the POINTERS keyword.
	COL	= Column in the binary table to place data in.   May be either
                 a list of column numbers where the first column is one, or 
                 a string list of column names.  

 OPTIONAL INPUT KEYWORDS: 
	ROW	= Either row number in the binary table to write data to,
		  starting from row one, or a two element array containing a
		  range of row numbers to write.  If not passed, then
		  the entire column is written.
	NANVALUE= Value signalling data dropout.  All points corresponding to
		  this value are set to be IEEE NaN (not-a-number).  Ignored
		  unless DATA is of type float, double-precision or complex.
       NOSCALE = If set, then TSCAL/TZERO values are ignored, and data is 
                 written exactly as supplied. 
       PASS_METHOD = A scalar string indicating method of passing
                 data to FXBWRITM.  One of 'ARGUMENT' (indicating
                 pass by positional argument),  or'POINTER' (indicating
                 passing an array of pointers by the POINTERS
                 keyword).  
                 Default:  'ARGUMENT'
       POINTERS = If PASS_METHOD is 'POINTER' then the user must pass
                 an array of IDL pointers to this keyword, one for
                 each column.    Ultimately the user is responsible for 
                 deallocating pointers.
       BUFFERSIZE = Data are transferred in chunks to conserve
                 memory.  This is the size in bytes of each chunk.
                 If a value of zero is given, then all of the data
                 are transferred in one pass.  Default is 32768 (32
                 kB).
 OPTIONAL OUTPUT KEYWORDS:
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXBWRITE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...
       WARNMSG = Messages which are considered to be non-fatal
                 "warnings" are returned in this  output string.
       STATUS  = An output array containing the status for each
                 read, 1 meaning success and 0 meaning failure.

 PROCEDURE CALLS: 
      None.
 EXAMPLE:
      Write a binary table 'sample.fits' giving 43 X,Y positions and a 
      21 x 21 PSF at each position:

      (1) First, create sample values
      x = findgen(43) & y = findgen(43)+1 & psf = randomn(seed,21,21,43)
      
      (2) Create primary header, write it to disk, and make extension header
      fxhmake,header,/initialize,/extend,/date
      fxwrite,'sample.fits',header
      fxbhmake,header,43,'TESTEXT','Test binary table extension'

      (3) Fill extension header with desired column names
      fxbaddcol,1,header,x[0],'X'             ;Use first element in each array
      fxbaddcol,2,header,y[0],'Y'             ;to determine column properties
      fxbaddcol,3,header,psf[*,*,0],'PSF'

      (4) Write extension header to FITS file
      fxbcreate,unit,'sample.fits',header

      (5) Use FXBWRITM to write all data to the extension in a single call
      fxbwritm,unit,['X','Y','PSF'], x, y, psf
      fxbfinish,unit                 ;Close the file

 COMMON BLOCKS: 
	Uses common block FXBINTABLE--see "fxbintable.pro" for more
	information.
 RESTRICTIONS: 
	The binary table file must have been opened with FXBCREATE or
       FXBOPEN (with write access).

	The data must be consistent with the column definition in the binary
	table header.

	The row number must be consistent with the number of rows stored in the
	binary table header.

       A PASS_METHOD of POINTER does not use the EXECUTE() statement and can be
       used with the IDL Virtual Machine.   However, the EXECUTE() statement is
       used when the PASS_METHOD is by arguments.      
 CATEGORY: 
	Data Handling, I/O, FITS, Generic.
 PREVIOUS HISTORY: 
       C. Markwardt, based on FXBWRITE and FXBREADM (ver 1), Jan 1999
 WRITTEN: 
	Craig Markwardt, GSFC, January 1999.
 MODIFIED:
       Version 1, Craig Markwardt, GSFC 18 January 1999.
               Documented this routine, 18 January 1999. 
       C. Markwardt, added ability to pass by handle or pointer.
               Some bug fixes, 20 July 2001  
       W. Landsman/B.Schulz  Allow more than 50 arguments when using pointers
       W. Landsman  Remove pre-V5.0 HANDLE options      July 2004
       W. Landsman Remove EXECUTE() call with POINTERS   May 2005
       C. Markwardt Allow the output table to have TSCAL/TZERO
          keyword values; if that is the case, then the passed values
          will be quantized to match those scale factors before being
          written.  Sep 2007
       E. Hivon: write 64bit integer and double precison columns, Mar 2008
       C. Markwardt Allow unsigned integers, which have special
          TSCAL/TZERO values.  Feb 2009
       C. Markwardt Add support for files larger than 2 GB, 2012-04-17

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxbwritm.pro)

FXFINDEND

 NAME: 
	FXFINDEND
 Purpose     : 
	Find the end of a FITS file.
 Explanation : 
	This routine finds the end of the last logical record in a FITS file,
	which may be different from that of the physical end of the file.  Each
	FITS header is read in and parsed, and the file pointer is moved to
	where the next FITS extension header would be if there is one, or to
	the end of the file if not.
 Use         : 
	FXFINDEND, UNIT [, EXTENSION]
 Inputs      : 
	UNIT	= Logical unit number for the opened file.
 Opt. Inputs : 
	None.
 Outputs     : 
	None.
 Opt. Outputs: 
       EXTENSION = The extension number that a new extension would
                   have if placed at the end of the file.
 Keywords    : 
	None.
 Calls       : 
	FXHREAD, FXPAR
 Common      : 
	None.
 Restrictions: 
	The file must have been opened for block I/O.  There must not be any
	FITS "special records" at the end of the file.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Feb. 1992.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
 Version     : 
	Version 1, 12 April 1993.
	Converted to IDL V5.0   W. Landsman   September 1997
       Added EXTENSION parameter, CM 1999 Nov 18
       Allow for possible 64bit integer number of bytes W. Landsman Nov 2007
       make Ndata a long64 to deal with large files. E. Hivon Mar 2008

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxfindend.pro)

FXHCLEAN

 NAME: 
	FXHCLEAN
 Purpose     : 
	Removes required keywords from FITS header.
 Explanation : 
	Removes any keywords relevant to array structure from a FITS header,
	preparatory to recreating it with the proper values.
 Use         : 
	FXHCLEAN, HEADER
 Inputs      : 
	HEADER	= FITS header to be cleaned.
 Opt. Inputs : 
	None.
 Outputs     : 
	HEADER	= The cleaned FITS header is returned in place of the input
		  array.
 Opt. Outputs: 
	None.
 Keywords    : 
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXHCLEAN, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	SXDELPAR, FXPAR
 Common      : 
	None.
 Restrictions: 
	HEADER must be a string array containing a properly formatted FITS
	header.
 Side effects: 
	Warning:  when cleaning a binary table extension header, not all of the
	keywords pertaining to columns in the table may be removed.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Jan 1992.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 4, William Thompson, GSFC, 30 December 1994
		Added TCUNIn to list of column keywords to be removed.
 Version     :
       Version 4, 30 December 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxhclean.pro)

FXHMAKE

 NAME: 
	FXHMAKE
 Purpose     : 
	Create a basic FITS header array.
 Explanation : 
	Creates a basic header array with all the required keywords.  This
	defines a basic structure which can then be added to or modified by
	other routines.
 Use         : 
	FXHMAKE, HEADER  [, DATA ]
 Inputs      : 
	None required.
 Opt. Inputs : 
	DATA	= IDL data array to be written to file.    It must be in the 
                  primary data unit unless the XTENSION keyword is supplied.
		  This array is used to determine the values of the BITPIX and 
                 NAXIS, etc. keywords.

		  If not passed, then BITPIX is set to eight, NAXIS is set to
		  zero, and no NAXISnnn keywords are included in this
		  preliminary header.
 Outputs     : 
	HEADER = String array containing FITS header.
 Opt. Outputs: 
	None.
 Keywords    : 
	INITIALIZE = If set, then the header is completely initialized, and any
		     previous entries are lost.
	EXTEND	= If set, then the keyword EXTEND is inserted into the file,
		  with the value of "T" (true).
	DATE	= If set, then the DATE keyword is added to the header.
	ERRMSG	= If defined and passed, then any error messages will be
		  returned to the user in this parameter rather than
		  depending on the MESSAGE routine in IDL.  If no errors are
		  encountered, then a null string is returned.  In order to
		  use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXHMAKE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...
       XTENSION - If set, then the header is appropriate for an image 
                  extension, rather than the primary data unit.
 Calls       : 
	GET_DATE, FXADDPAR, FXHCLEAN
 Common      : 
	None.
 Restrictions: 
	Groups are not currently supported.
 Side effects: 
	BITPIX, NAXIS, etc. are defined such that complex arrays are stored as
	floating point, with an extra first dimension of two elements (real and
	imaginary parts).
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Jan 1992, from SXHMAKE by D. Lindler and M. Greason.
	Differences include:

		* Use of FITS standard (negative BITPIX) to signal floating
		  point numbers instead of (SDAS/Geis) DATATYPE keyword.
		* Storage of complex numbers as pairs of real numbers.
		* Support for EXTEND keyword, and for cases where there is no
		  primary data array.
		* Insertion of DATE record made optional.  Only required FITS
		  keywords are inserted automatically.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 21 June 1994
		Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
	Version 4, Wayne Landsman, GSFC, 12 August 1997
		Recognize double complex data type
	Converted to IDL V5.0   W. Landsman   September 1997
       Version 6, William Thompson, GSFC, 22 September 2004
               Recognize unsigned integer types.
       Version 6.1, C. Markwardt, GSFC, 19 Jun 2005
               Add the XTENSION keyword, which writes an XTENSION
               keyword instead of SIMPLE.
 Version     :
       Version 6.1, 19 June 2005

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxhmake.pro)

FXHMODIFY

 NAME: 
       FXHMODIFY
 PURPOSE     : 
       Modify a FITS header in a file on disk.
 Explanation : 
       Opens a FITS file, and adds or modifies a parameter in the FITS header.
       Can be used for either the main header, or for an extension header. 
       The modification is performed directly on the disk file.
 Use         : 
       FXHMODIFY, FILENAME, NAME, VALUE, COMMENT
 Inputs      : 
       FILENAME = String containing the name of the file to be read.

       NAME    = Name of parameter, scalar string  If NAME is already in the 
                 header the value and possibly comment fields are modified. 
                 Otherwise a new record is added to the header.  If NAME is 
                 equal to either "COMMENT" or "HISTORY" then the value will be 
                 added to the record without replacement.  In this case the 
                 comment parameter is ignored.

       VALUE   = Value for parameter.  The value expression must be of the
                 correct type, e.g. integer, floating or string.  String
                 values of 'T' or 'F' are considered logical values.

 Opt. Inputs : 
       COMMENT = String field.  The '/' is added by this routine.  Added
                 starting in position 31.  If not supplied, or set equal to ''
                 (the null string), then any previous comment field in the
                 header for that keyword is retained (when found).
 Outputs     : 
       None.
 Opt. Outputs: 
       None.
 Keywords    : 
       EXTENSION = Either the number of the FITS extension, starting with the
                   first extension after the primary data unit being one; or a
                   character string containing the value of EXTNAME to search
                   for.  If not passed, then the primary FITS header is
                   modified.           

       BEFORE  = Keyword string name.  The parameter will be placed before the
                 location of this keyword.  For example, if BEFORE='HISTORY'
                 then the parameter will be placed before the first history
                 location.  This applies only when adding a new keyword;
                 keywords already in the header are kept in the same position.

       AFTER   = Same as BEFORE, but the parameter will be placed after the
                 location of this keyword.  This keyword takes precedence over
                 BEFORE.

       FORMAT  = Specifies FORTRAN-like format for parameter, e.g. "F7.3".  A
                 scalar string should be used.  For complex numbers the format
                 should be defined so that it can be applied separately to the
                 real and imaginary parts.
       ERRMSG  = If defined and passed, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.  In order to
                 use this feature, ERRMSG must be defined first, e.g.

                       ERRMSG = ''
                       FXHMODIFY, ERRMSG=ERRMSG, ...
                       IF ERRMSG NE '' THEN ...

 Calls       : 
       FXHREAD, FXPAR, FXADDPAR, BLKSHIFT
 Restrictions: 
       This routine can not be used to modify any of the keywords that control
       the structure of the FITS file, e.g. BITPIX, NAXIS, PCOUNT, etc.  Doing
       so could corrupt the readability of the FITS file.
 Example:
       Modify the name 'OBJECT' keyword in the primary FITS header of a FITS 
       file 'spec98.ccd' to contain the value 'test domeflat'

       IDL> fxhmodify, 'spec98.ccd', 'OBJECT', 'test domeflat'

 Side effects: 
       If adding a record to the FITS header would increase the
       number of 2880 byte records stored on disk, then the file is
       enlarged before modification, unless the NOGROW keyword is passed.
  
 Category    : 
       Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
       None.
 Written     : 
       William Thompson, GSFC, 3 March 1994.
 Modified    : 
       Version 1, William Thompson, GSFC, 3 March 1994.
       Version 2, William Thompson, GSFC, 31 May 1994
               Added ERRMSG keyword.
       Version 3, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
      Version 3.1 Wayne Landsman GSFC   17 March 2006
               Fix problem in BLKSHIFT call if primary header  extended
       Version 3.2 W. Landsman 14 November 204 
               Allow for need for 64bit number of bytes
; Version     :
       Version 3.2, 14 Nov 2007

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxhmodify.pro)

FXHREAD

 NAME: 
	FXHREAD
 Purpose     : 
       Reads a FITS header from an opened disk file.
 Explanation : 
       Reads a FITS header from an opened disk file.
 Use         : 
	FXHREAD, UNIT, HEADER  [, STATUS ]
 Inputs      : 
	UNIT	= Logical unit number.
 Opt. Inputs : 

 Outputs     : 
	HEADER	= String array containing the FITS header.
 Opt. Outputs: 
	STATUS	= Condition code giving the status of the read.  Normally, this
		  is zero, but is set to !ERR if an error occurs, or if the
		  first byte of the header is zero (ASCII null).
 Keywords    : 
	None.
 Calls       : 
	None.
 Common      : 
	None.
 Restrictions: 
	The file must already be positioned at the start of the header.  It
	must be a proper FITS file.
 Side effects: 
	The file ends by being positioned at the end of the FITS header, unless
	an error occurs.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Feb 1992, from READFITS by J. Woffard and W. Landsman.
	W. Thompson, Aug 1992, added test for SIMPLE keyword.
 Written     : 
	William Thompson, GSFC, February 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
 Version     : 
	Version 1, 12 April 1993.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxhread.pro)

FXMOVE

 NAME:
     FXMOVE
 PURPOSE:
     Skip to a specified extension number or name in a FITS file

 CALLING SEQUENCE:
     STATUS=FXMOVE(UNIT, EXT, /Silent)
     STATUS=FXMOVE(UNIT, EXTNAME, /Silent, EXT_NO=, ERRMSG= )

 INPUT PARAMETERS:
     UNIT     = An open unit descriptor for a FITS data stream.
     EXTEN   = Number of extensions to skip.
                              or
             Scalar string giving extension name (in the EXTNAME keyword)           
 OPTIONAL INPUT PARAMETER:
     /SILENT - If set, then any messages about invalid characters in the 
               FITS file are suppressed.
 OPTIONAL OUTPUT PARAMETER:
       ERRMSG  = If this keyword is present, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.

 RETURNS:
     0 if successful.
    -1 if an error is encountered.

 COMMON BLOCKS:
      None.
 SIDE EFFECTS:
      Repositions the file pointer.
 PROCEDURE:
      Each FITS header is read in and parsed, and the file pointer is moved
      to where the next FITS extension header until the desired
      extension is reached.
 PROCEDURE CALLS:
      FXPAR(), MRD_HREAD, MRD_SKIP
 MODIFICATION HISTORY:
      Extracted from FXPOSIT 8-March-2000 by T. McGlynn
      Added /SILENT keyword  14-Dec-2000 by W. Landsman
      Save time by not reading the full header  W. Landsman   Feb. 2003
      Allow extension name to be specified, added EXT_NO, ERRMSG keywords
         W. Landsman  December 2006
      Make search for EXTNAME case-independent  W.Landsman March 2007 
      Avoid round-off error for very large extensions N. Piskunov Dec 2007
      Assume since V6.1 (/INTEGER keyword available to PRODUCT() ) Dec 2007
      Capture error message from MRD_HREAD (must be used with post-June 2009
        version of MRD-HREAD)   W. Landsman  July 2009

(See $IDLUTILS_DIR/goddard/pro/fits/fxmove.pro)

FXPAR()

 NAME: 
        FXPAR()
 PURPOSE: 
       Obtain the value of a parameter in a FITS header.
 EXPLANATION: 
       The first 8 chacters of each element of HDR are searched for a match to
       NAME.  If the keyword is one of those allowed to take multiple values
       ("HISTORY", "COMMENT", or "        " (blank)), then the value is taken
       as the next 72 characters.  Otherwise, it is assumed that the next
       character is "=", and the value (and optional comment) is then parsed
       from the last 71 characters.  An error occurs if there is no parameter
       with the given name.
      
       If the value is too long for one line, it may be continued on to the
       the next input card, using the CONTINUE Long String Keyword convention.
       For more info, http://fits.gsfc.nasa.gov/registry/continue_keyword.html
       

       Complex numbers are recognized as two numbers separated by one or more
       space characters.

       If a numeric value has no decimal point (or E or D) it is returned as
       type LONG.  If it contains more than 8 numerals, or contains the
       character 'D', then it is returned as type DOUBLE.  Otherwise it is
       returned as type FLOAT.    If an integer is too large to be stored as
       type LONG, then it is returned as DOUBLE.

 CALLING SEQUENCE: 
       Result = FXPAR( HDR, NAME  [, ABORT, COUNT=, COMMENT=, /NOCONTINUE ] )

       Result = FXPAR(HEADER,'DATE')           ;Finds the value of DATE
       Result = FXPAR(HEADER,'NAXIS*')         ;Returns array dimensions as
                                               ;vector
 REQUIRED INPUTS: 
       HDR     = FITS header string array (e.g. as returned by FXREAD).  Each
                 element should have a length of 80 characters
       NAME    = String name of the parameter to return.  If NAME is of the
                 form 'keyword*' then an array is returned containing values
                 of keywordN where N is an integer.  The value of keywordN
                 will be placed in RESULT(N-1).  The data type of RESULT will
                 be the type of the first valid match of keywordN
                 found, unless DATATYPE is given.
 OPTIONAL INPUT: 
       ABORT   = String specifying that FXPAR should do a RETALL if a
                 parameter is not found.  ABORT should contain a string to be
                 printed if the keyword parameter is not found.  If not
                 supplied, FXPAR will return with a negative !err if a keyword
                 is not found.
       DATATYPE = A scalar value, indicating the type of vector
                  data.  All keywords will be cast to this type.
                  Default: based on first keyword.
                  Example: DATATYPE=0.0D (cast data to double precision)
       START   = A best-guess starting position of the sought-after
                 keyword in the header.  If specified, then FXPAR
                 first searches for scalar keywords in the header in
                 the index range bounded by START-PRECHECK and
                 START+POSTCHECK.  This can speed up keyword searches
                 in large headers.  If the keyword is not found, then
                 FXPAR searches the entire header.  

                 If not specified then the entire header is searched.
                 Searches of the form 'keyword*' also search the
                 entire header and ignore START.

                 Upon return START is changed to be the position of
                 the newly found keyword.  Thus the best way to
                 search for a series of keywords is to search for
                 them in the order they appear in the header like
                 this:

                       START = 0L
                       P1 = FXPAR('P1', START=START)
                       P2 = FXPAR('P2', START=START)
       PRECHECK = If START is specified, then PRECHECK is the number
                  of keywords preceding START to be searched.
                  Default: 5
       POSTCHECK = If START is specified, then POSTCHECK is the number
                   of keywords after START to be searched.
                   Default: 20
 OUTPUT: 
       The returned value of the function is the value(s) associated with the
       requested keyword in the header array.

       If the parameter is complex, double precision, floating point, long or
       string, then the result is of that type.  Apostrophes are stripped from
       strings.  If the parameter is logical, 1 is returned for T, and 0 is
       returned for F.

       If NAME was of form 'keyword*' then a vector of values are returned.

 OPTIONAL INPUT KEYWORDS: 
       /NOCONTINUE = If set, then continuation lines will not be read, even
                 if present in the header
 OPTIONAL OUTPUT KEYWORD:
       COUNT   = Optional keyword to return a value equal to the number of
                 parameters found by FXPAR.
       COMMENTS= Array of comments associated with the returned values.

 PROCEDURE CALLS: 
       GETTOK(), VALID_NUM
 SIDE EFFECTS: 

       The system variable !err is set to -1 if parameter not found, 0 for a
       scalar value returned.  If a vector is returned it is set to the number
       of keyword matches found.

       If a keyword occurs more than once in a header, a warning is given,
       and the first occurence is used.  However, if the keyword is "HISTORY",
       "COMMENT", or "        " (blank), then multiple values are returned.

 NOTES:
	The functions SXPAR() and FXPAR() are nearly identical, although
	FXPAR() has slightly more sophisticated parsing.   There is no
	particular reason for having two nearly identical procedures, but
	both are too widely used to drop either one.

 REVISION HISTORY: 
       Version 1, William Thompson, GSFC, 12 April 1993.
               Adapted from SXPAR
       Version 2, William Thompson, GSFC, 14 October 1994
               Modified to use VALID_NUM instead of STRNUMBER.  Inserted
               additional call to VALID_NUM to trap cases where character
               strings did not contain quotation marks.
       Version 3, William Thompson, GSFC, 22 December 1994
               Fixed bug with blank keywords, following suggestion by Wayne
               Landsman.
       Version 4, Mons Morrison, LMSAL, 9-Jan-98
               Made non-trailing ' for string tag just be a warning (not
               a fatal error).  It was needed because "sxaddpar" had an
               error which did not write tags properly for long strings
               (over 68 characters)
       Version 5, Wayne Landsman GSFC, 29 May 1998
               Fixed potential problem with overflow of LONG values
       Version 6, Craig Markwardt, GSFC, 28 Jan 1998, 
               Added CONTINUE parsing         
       Version 7, Craig Markwardt, GSFC, 18 Nov 1999,
               Added START, PRE/POSTCHECK keywords for better
               performance
       Version 8, Craig Markwardt, GSFC, 08 Oct 2003,
               Added DATATYPE keyword to cast vector keywords type
       Version 9, Paul Hick, 22 Oct 2003, Corrected bug (NHEADER-1)
       Version 10, W. Landsman, GSFC  2 May 2012
               Keywords of form "name_0" cound confuse vector extractions

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxpar.pro)

FXPARPOS()

 NAME: 
	FXPARPOS()
 Purpose     : 
	Finds position to insert record into FITS header.
 Explanation : 
	Finds the position to insert a record into a FITS header.  Called from
	FXADDPAR.
 Use         : 
	Result = FXPARPOS(KEYWRD, IEND  [, BEFORE=BEFORE ]  [, AFTER=AFTER ])
 Inputs      : 
	KEYWRD	= Array of eight-character keywords in header.
	IEND	= Position of END keyword.
 Opt. Inputs : 
	None.
 Outputs     : 
	Result of function is position to insert record.
 Opt. Outputs: 
	None.
 Keywords    : 
	BEFORE	= Keyword string name.  The parameter will be placed before the
		  location of this keyword.  For example, if BEFORE='HISTORY'
		  then the parameter will be placed before the first history
		  location.  This applies only when adding a new keyword;
		  keywords already in the header are kept in the same position.

	AFTER	= Same as BEFORE, but the parameter will be placed after the
		  location of this keyword.  This keyword takes precedence over
		  BEFORE.

	If neither BEFORE or AFTER keywords are passed, then IEND is returned.

 Calls       : 
	None.
 Common      : 
	None.
 Restrictions: 
	KEYWRD and IEND must be consistent with the relevant FITS header.
 Side effects: 
	None.
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	William Thompson, Jan 1992.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
 Version     : 
	Version 1, 12 April 1993.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxparpos.pro)

FXPOSIT

NAME:
FXPOSIT
PURPOSE:
Return the unit number of a FITS file positioned at specified extension
EXPLANATION:
The FITS file will be ready to be read at the beginning of the
specified extension. Either an extension number or extension name
can be specified. Called by headfits.pro, mrdfits.pro

Modified in March 2009 to set the /SWAP_IF_LITTLE_ENDIAN keyword
when opening a file, and **may not be compatible with earlier versions**
CALLING SEQUENCE:
unit=FXPOSIT(FILE, EXT_NO_OR_NAME, /READONLY, COMPRESS=program,
UNIXPIPE=, ERRMSG= , EXTNUM= , UNIT=, /SILENT
/FPACK, /NO_FPACK

INPUT PARAMETERS:
FILE = FITS file name, scalar string. If an empty string is supplied
then the user will be prompted for the file name. The user
will also be prompted if a wild card is supplied, and more than
one file matches the wildcard.
EXT_NO_OR_NAME = Either the extension to be moved to (scalar
nonnegative integer) or the name of the extension to read
(scalar string)

RETURNS:
Unit number of file or -1 if an error is detected.

OPTIONAL INPUT KEYWORD PARAMETER:
COMPRESS - If this keyword is set and non-zero, then then treat
the file as compressed. If 1 assume a gzipped file.
and use IDLs internal decompression facility. For Unix
compressed or bzip2 compressed files spawn off a process to
decompress and use its output as the FITS stream. If the
keyword is not 1, then use its value as a string giving the
command needed for decompression.
/FPACK - Signal that the file is compressed with the FPACK software.
http://heasarc.gsfc.nasa.gov/fitsio/fpack/ ) By default,
(FXPOSIT will assume that if the file name extension ends in
.fz that it is fpack compressed.) The FPACK software must
be installed on the system
/NO_FPACK - The unit will only be used to read the FITS header. In
that case FPACK compressed files need not be uncompressed.
LUNIT - Integer giving the file unit number. Use this keyword if
you want to override the default use of GET_LUN to obtain
a unit number.
/READONLY - If this keyword is set and non-zero, then OPENR rather
than OPENU will be used to open the FITS file. Note that
compressed files are always set to /READONLY
/SILENT If set, then suppress any messages about invalid characters
in the FITS file.

OPTIONAL OUTPUT KEYWORDS:
EXTNUM - Nonnegative integer give the extension number actually read
Useful only if the extension was specified by name.
ERRMSG = If this keyword is present, then any error messages will be
returned to the user in this parameter rather than
depending on the MESSAGE routine in IDL. If no errors are
encountered, then a null string is returned.
UNIXPIPE - If set to 1, then the FITS file was opened with a UNIX pipe
rather than with the OPENR command. This is only required
when reading a FPACK, bzip or Unix compressed file. Note
that automatic byteswapping cannnot be set for a Unix pipe,
since the SWAP_IF_LITTLE_ENDIAN keyword is only available for the
OPEN command, and it is the responsibilty of the calling
routine to perform the byteswapping.
SIDE EFFECTS:
Opens and returns a file unit.
PROCEDURE:
Open the appropriate file, or spawn a command and intercept
the output.
Call FXMOVE to get to the appropriate extension.
PROCEDURE CALLS:
FXMOVE()
MODIFICATION HISTORY:
Derived from William Thompson's FXFINDEND routine.
Modified by T.McGlynn, 5-October-1994.
Modified by T.McGlynn, 25-Feb-1995 to handle compressed
files. Pipes cannot be accessed using FXHREAD so
MRD_HREAD was written.
W. Landsman 23-Apr-1997 Force the /bin/sh shell when uncompressing
T. McGlynn 03-June-1999 Use /noshell option to get rid of processes left by spawn.
Use findfile to retain ability to use wildcards
W. Landsman 03-Aug-1999 Use EXPAND_TILDE under Unix to find file
T. McGlynn 04-Apr-2000 Put reading code into FXMOVE,
additional support for compression from D.Palmer.
W. Landsman/D.Zarro 04-Jul-2000 Added test for !VERSION.OS EQ 'Win32' (WinNT)
W. Landsman 12-Dec-2000 Added /SILENT keyword
W. Landsman April 2002 Use FILE_SEARCH for V5.5 or later
W. Landsman Feb 2004 Assume since V5.3 (OPENR,/COMPRESS available)
W. Landsman,W. Thompson, 2-Mar-2004, Add support for BZIP2
W. Landsman Don't leave open file if an error occurs
W. Landsman Sep 2004 Treat FTZ extension as gzip compressed
W. Landsman Feb 2006 Removed leading spaces (prior to V5.5)
W. Landsman Nov 2006 Allow specification of extension name
Added EXTNUM, ERRMSG keywords
W. Landsman/N.Piskunov Dec 2007 Added LUNIT keyword
W. Landsman Mar 2009 OPEN with /SWAP_IF_LITTLE_ENDIAN
Added UNIXPIPE output keyword
N. Rich May 2009 Check if filename is an empty string
W. Landsman May 2009 Support FPACK compressed files
Added /FPACK, /HEADERONLY keywords
W.Landsman July 2009 Deprecated /HEADERONLY add /NO_FPACK
W.Landsman July 2011 Check for SIMPLE in first 8 chars
Use gunzip to decompress Unix. Z file since compress utility
often not installed anymore)

(See $IDLUTILS_DIR/goddard/pro/fits/fxposit.pro)

FXREAD

 NAME: 
	FXREAD
 Purpose     : 
	Read basic FITS files.
 Explanation : 
	Read an image array from a disk FITS file.  Optionally allows the
	user to read in only a subarray and/or every Nth pixel.
 Use         : 
	FXREAD, FILENAME, DATA  [, HEADER  [, I1, I2  [, J1, J2 ]]  [, STEP]]
 Inputs      : 
	FILENAME = String containing the name of the file to be read.
 Opt. Inputs : 
	I1,I2	 = Data range to read in the first dimension.  If passed, then
		   HEADER must also be passed.  If not passed, or set to -1,-1,
		   then the entire range is read.
	J1,J2	 = Data range to read in the second dimension.  If passed, then
		   HEADER and I1,J2 must also be passed.  If not passed, or set
		   to -1,-1, then the entire range is read.
	STEP	 = Step size to use in reading the data.  If passed, then
		   HEADER must also be passed.  Default value is 1.  Ignored if
		   less than 1.
 Outputs     : 
	DATA	 = Data array to be read from the file.
 Opt. Outputs: 
	HEADER	 = String array containing the header for the FITS file.
 Keywords    : 
       /COMPRESS - If this keyword is set and non-zero, then then treat
                the file as gzip compressed.    By default FXREAD assumes
                the file is gzip compressed if it ends in ".gz"
	NANVALUE = Value signalling data dropout.  All points corresponding to
		   IEEE NaN (not-a-number) are set to this value.  Ignored
		   unless DATA is of type float or double-precision.
       EXTENSION = FITS extension.  It can be a scalar integer,
                indicating the extension number (extension number 0
                is the primary HDU).  It can also be a scalar string,
                indicating the extension name (EXTNAME keyword).
                Default: 0 (primary HDU)
	PROMPT	 = If set, then the optional parameters are prompted for at the
		   keyboard.
	AVERAGE	 = If set, then the array size is reduced by averaging pixels
		   together rather than by subselecting pixels.  Ignored unless
		   STEP is nontrivial.  Note:  this is much slower.
	YSTEP	 = If passed, then STEP is the step size in the 1st dimension,
		   and YSTEP is the step size in the 2nd dimension.  Otherwise,
		   STEP applies to both directions.
	NOSCALE	 = If set, then the output data will not be scaled using the
		   optional BSCALE and BZERO keywords in the FITS header.
		   Default is to scale, if and only if BSCALE and BZERO are
		   present and nontrivial.
	NOUPDATE = If set, then the optional BSCALE and BZERO keywords in the
		   optional HEADER array will not be changed.  The default is
		   to reset these keywords to BSCALE=1, BZERO=0.  Ignored if
		   NOSCALE is set.
	ERRMSG   = If defined and passed, then any error messages will be
		   returned to the user in this parameter rather than
		   depending on the MESSAGE routine in IDL.  If no errors are
		   encountered, then a null string is returned.  In order to
		   use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXREAD, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...
       NODATA   = If set, then the array is not read in, but the
                  primary header is read.

 Calls       : 
	GET_DATE, IEEE_TO_HOST, FXADDPAR, FXHREAD, FXPAR, WHERENAN
 Common      : 
	None.
 Restrictions: 
	Groups are not supported.

	The optional parameters I1, I2, and STEP only work with one or
	two-dimensional arrays.  J1 and J2 only work with two-dimensional
	arrays.

	Use of the AVERAGE keyword is not compatible with arrays with missing
	pixels.

 Side effects: 
	If the keywords BSCALE and BZERO are present in the FITS header, and
	have non-trivial values, then the returned array DATA is formed by the
	equation

			DATA = BSCALE*original + BZERO

	However, this behavior can overridden by using the /NOSCALE keyword.

	If the data is scaled, then the optional HEADER array is changed so
	that BSCALE=1 and BZERO=0.  This is so that these scaling parameters
	are not applied to the data a second time by another routine.  Also,
	history records are added storing the original values of these
	constants.  Note that only the returned array is modified--the header
	in the FITS file itself is untouched.

	If the /NOUPDATE keyword is set, however, then the BSCALE and BZERO
	keywords are not changed.  It is then the user's responsibility to
	ensure that these parameters are not reapplied to the data.  In
	particular, these keywords should not be present in any header when
	writing another FITS file, unless the user wants their values to be
	applied when the file is read back in.  Otherwise, FITS readers will
	read in the wrong values for the data array.
	
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, May 1992, based in part on READFITS by W. Landsman, and
			       STSUB by M. Greason and K. Venkatakrishna.
	W. Thompson, Jun 1992, added code to interpret BSCALE and BZERO
			       records, and added NOSCALE and NOUPDATE
			       keywords.
	W. Thompson, Aug 1992, changed to call FXHREAD, and to add history
			       records for BZERO, BSCALE.
 Minimium IDL Version:
       V5.3 (uses COMPRESS keyword to OPEN) 
 Written     : 
	William Thompson, GSFC, May 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 17 November 1993.
		Corrected bug with AVERAGE keyword on non-IEEE compatible
		machines.
		Corrected bug with subsampling on VAX machines.
	Version 3, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
       Version 4, William Thompson, GSFC, 23 June 1994
               Modified so that ERRMSG is not touched if not defined.
       Version 5, Zarro (SAC/GSFC), 14 Feb 1997 
               Added I/O error checking
       Version 6, 20-May-1998, David Schlegel/W. Thompson
               Allow a single pixel to be read in.
               Change the signal to read in the entire array to be -1
       Version 7 C. Markwardt 22 Sep 2003
               If the image is empty (NAXIS EQ 0), or NODATA is set, then
               return only the header.  
       Version 8 W. Landsman  29 June 2004
               Added COMPRESS keyword, check for .gz extension  
       Version 9, William Thompson, 19-Aug-2004
               Make sure COMPRESS is treated as a scalar
       Version 10, Craig Markwardt, 01 Mar 2004
               Add EXTENSION keyword and ability to read different
               extensions than the primary one.
       Version 11,  W. Landsamn   September 2006 
               Assume since V5.5, remove VMS support
       Version 11.1,  W. Landsamn   November 2007
               Allow for possibility number of bytes requires 64 bit integer
       Version 12, William Thompson, 18-Jun-2010, update BLANK value.

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxread.pro)

FXWRITE

 NAME: 
	FXWRITE
 Purpose     : 
	Write a disk FITS file.
 Explanation : 
       Creates or appends to a disk FITS file and writes a FITS
       header, and optionally an image data array.
 Use         : 
	FXWRITE, FILENAME, HEADER [, DATA ]
 Inputs      : 
	FILENAME = String containing the name of the file to be written.
	HEADER	 = String array containing the header for the FITS file.
 Opt. Inputs : 
	DATA	 = IDL data array to be written to the file.  If not passed,
		   then it is assumed that extensions will be added to the
		   file.
 Outputs     : 
	None.
 Opt. Outputs: 
	None.
 Keywords    : 
	NANVALUE = Value signalling data dropout.  All points corresponding to
		   this value are set to be IEEE NaN (not-a-number).  Ignored
		   unless DATA is of type float, double-precision or complex.
	NOUPDATE = If set, then the optional BSCALE and BZERO keywords in the
		   HEADER array will not be changed.  The default is to reset
		   these keywords to BSCALE=1, BZERO=0.
       APPEND = If set, then an existing file will be appended to.
                Appending to a non-existent file will create it.  If
                a primary HDU already exists then it will be modified
                to have EXTEND = T.
	ERRMSG	 = If defined and passed, then any error messages will be
		   returned to the user in this parameter rather than
		   depending on the MESSAGE routine in IDL.  If no errors are
		   encountered, then a null string is returned.  In order to
		   use this feature, ERRMSG must be defined first, e.g.

			ERRMSG = ''
			FXWRITE, ERRMSG=ERRMSG, ...
			IF ERRMSG NE '' THEN ...

 Calls       : 
	CHECK_FITS, GET_DATE, HOST_TO_IEEE, FXADDPAR, FXPAR
 Common      : 
	None.
 Restrictions: 
	If DATA is passed, then HEADER must be consistent with it.  If no data
	array is being written to the file, then HEADER must also be consistent
	with that.  The routine FXHMAKE can be used to create a FITS header.

	If found, then the optional keywords BSCALE and BZERO in the HEADER
	array is changed so that BSCALE=1 and BZERO=0.  This is so that these
	scaling parameters are not applied to the data a second time by another
	routine.  Also, history records are added storing the original values
	of these constants.  (Other values of BZERO are used for unsigned
	integers.)

	If the /NOUPDATE keyword is set, however, then the BSCALE and BZERO
	keywords are not changed.  The user should then be aware that FITS
	readers will apply these numbers to the data, even if the data is
	already converted to floating point form.

	Groups are not supported.

 Side effects: 
	HEADER may be modified.  One way it may be modified is describe
       above under NOUPDATE.  The first header card may also be
       modified to conform to the FITS standard if it does not
       already agree (i.e. use of either the SIMPLE or XTENSION
       keyword depending on whether the image is the primary HDU or
       not).
 Category    : 
	Data Handling, I/O, FITS, Generic.
 Prev. Hist. : 
	W. Thompson, Jan 1992, from WRITEFITS by J. Woffard and W. Landsman.
	Differences include:

		* Made DATA array optional, and HEADER array mandatory.
		* Changed order of HEADER and DATA parameters.
		* No attempt made to fix HEADER array.

	W. Thompson, May 1992, changed open statement to force 2880 byte fixed
			       length records (VMS).  The software here does not
			       depend on this file configuration, but other
			       FITS readers might.
	W. Thompson, Aug 1992, added code to reset BSCALE and BZERO records,
			       and added the NOUPDATE keyword.
 Written     : 
	William Thompson, GSFC, January 1992.
 Modified    : 
	Version 1, William Thompson, GSFC, 12 April 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 31 May 1994
		Added ERRMSG keyword.
	Version 3, William Thompson, GSFC, 23 June 1994
		Modified so that ERRMSG is not touched if not defined.
	Version 4, William Thompson, GSFC, 12 August 1999
		Catch error if unable to open file.
       Version 4.1 Wayne Landsman, GSFC, 02 May 2000
               Remove !ERR in call to CHECK_FITS, Use ARG_PRESENT()
       Version 5, William Thompson, GSFC, 22 September 2004
               Recognize unsigned integer types
       Version 5.1 W. Landsman 14 November 204 
               Allow for need for 64bit number of bytes
       Version 6, Craig Markwardt, GSFC, 30 May 2005
               Ability to append to existing files
 Version     : 
	Version 6, 30 May 2005

(See $IDLUTILS_DIR/goddard/pro/fits_bintable/fxwrite.pro)

F_FORMAT

 NAME:
	F_FORMAT
 PURPOSE:
	Choose a nice floating format for displaying an array of REAL data.
 EXPLANATION:
	Called by TVLIST, IMLIST.

 CALLING SEQUENCE:
	fmt = F_FORMAT( minval, maxval, factor, [ length ] )

 INPUTS:
	MINVAL - REAL scalar giving the minimum value of an array of numbers
		for which one desires a nice format.
	MAXVAL - REAL scalar giving maximum value in array of numbers

 OPTIONAL INPUT:
	LENGTH - length of the output F format (default = 5)
		must be an integer scalar > 2

 OUTPUT:
	FMT - an F or I format string, e.g. 'F5.1'
	FACTOR - factor of 10 by which to multiply array of numbers to achieve
		a pretty display using format FMT.

 EXAMPLE:
	Find a nice format to print an array of numbers with a minimum of 5.2e-3
	and a maximum  of 4.2e-2.

		IDL> fmt = F_FORMAT( 5.2e-3, 4.2e-2, factor )
         
	yields fmt = '(F5.2)' and factor = .01, i.e. the array can be displayed
	with a F5.2 format after multiplication by 100.

 REVISION HISTORY:
	Written W. Landsman              December 1988
	Deal with factors < 1.           August 1991
	Deal with factors < 1. *and* a large range    October 1992
	Now returns In format rather than Fn.0    February, 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/f_format.pro)

GALAGE

 NAME: 
   GALAGE

 PURPOSE:
   Determine the age of a galaxy given its redshift and a formation redshift.

 CALLING SEQUENCE:
   age = galage(z, [zform,  H0 =, k=, lambda0 =, Omega_m= , q0 =, /SILENT])' 

 INPUTS:
    z - positive numeric vector or scalar of measured redshifts 
    zform - redshift of galaxy formation (> z), numeric positive scalar 
        To determine the age of the universe at a given redshift, set zform
        to a large number (e.g. ~1000).

 OPTIONAL KEYWORD INPUTS: 
    H0 - Hubble constant in km/s/Mpc, positive scalar, default is 70
    /SILENT - If set, then the adopted cosmological parameters are not 
         displayed at the terminal.

        No more than two of the following four parameters should be
        specified.   None of them need be specified -- the adopted defaults
        are given. 
    k - curvature constant, normalized to the closure density.   Default is
        0, (indicating a flat universe)
    Omega_m -  Matter density, normalized to the closure density, default
        is 0.3.   Must be non-negative
    Lambda0 - Cosmological constant, normalized to the closure density,
        default is 0.7
    q0 - Deceleration parameter, numeric scalar = -R*(R'')/(R')^2, default
        is -0.55
       
 OUTPUTS:
    age -  age of galaxy in years, will have the same number of elements
           as the input Z vector

 EXAMPLE:
    (1) Determine the age of a galaxy observed at z = 1.5 in a cosmology with
    Omega_matter = 0.3 and Lambda = 0.0.    Assume the formation redshift was
    at z = 25, and use the default Hubble constant (=70 km/s/Mpc)

    IDL> print,galage(1.5,25,Omega_m=0.3, Lambda = 0)
             ===> 3.35 Gyr
     
    (2) Plot the age of a galaxy in Gyr out to a redshift of z = 5, assuming 
        the default cosmology (omega_m=0.3, lambda=0.7), and zform = 100

    IDL> z = findgen(50)/10.
    IDL> plot,z,galage(z,100)/1e9,xtit='z',ytit = 'Age (Gyr)'

 PROCEDURE:
    For a given formation time zform and a measured z, integrate dt/dz from 
    zform to z. Analytic formula of dt/dz in Gardner, PASP 110:291-305, 1998 
    March  (eq. 7)
 
 COMMENTS:
    (1) Integrates using the IDL Astronomy Library procedure QSIMP.    (The 
    intrinsic IDL QSIMP() function is not called because of its ridiculous
    restriction that only scalar arguments can be passed to the integrating
    function.)    The function 'dtdz' is defined at the beginning of the 
    routine (so it can compile first).
    
    (2) Should probably be fixed to use a different integrator from QSIMP when
    computing age from an "infinite" redshift of formation.    But using a 
    large value of zform seems to work adequately.

     (3) An alternative set of IDL procedures for computing cosmological
    parameters is available at 
            http://cerebus.as.arizona.edu/~ioannis/research/red/
 PROCEDURES CALLED:
    COSMO_PARAM, QSIMP
 HISTORY: 
     STIS version by P. Plait (ACC)                  June 1999
     IDL Astro Version   W. Landsman (Raytheon ITSS)      April 2000
     Avoid integer overflow for more than 32767 redshifts  July 2001

(See $IDLUTILS_DIR/goddard/pro/astro/galage.pro)

GAL_FLAT

 NAME:
	GAL_FLAT

 PURPOSE:
	Transforms the image of a galaxy so that the galaxy appears face-on
 EXPLANATION:
	Either a nearest-neighbor approximations or a bilinear interpolation 
	may  be used.

 CALLING SEQUENCE:
	RESULT = GAL_FLAT( image, ang, inc, [, cen, /INTERP ] )  

 INPUTS:   
	IMAGE  - Image to be transformed
	ANG  - Angle of major axis, counterclockwise from Y-axis, degrees
		For an image in standard orientation (North up, East left)
		this is the Position Angle
	INC - Angle of inclination of galaxy, degrees

 OPTIONAL INPUTS:
	CEN - Two element vector giving the X and Y position of galaxy center
		If not supplied, then the galaxy center is assumed to coincide
		 with the image center

 INPUT KEYWORDS:
	INTERP - If present, and non-zero, then bilinear interpolation will be
		performed.  Otherwise a nearest neighbor approximation  is used.

 OUTPUTS:
	RESULT - the transformed image, same dimensions and type as IMAGE

 METHOD:
	A set of 4 equal spaced control points are corrected for inclination
	using the procedure POLYWARP.   These control points are used by 
	POLY_2D to correct the whole image.

 REVISION HISTORY:
	Written by R. S. Hill, SASC Technologies Inc., 4 December 1985
	Code cleaned up a bit    W. Landsman      December 1992
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/gal_flat.pro)

GAL_UVW

 NAME:
     GAL_UVW
 PURPOSE:
     Calculate the Galactic space velocity (U,V,W) of star  
 EXPLANATION:
     Calculates the Galactic space velocity U, V, W of star given its 
     (1) coordinates, (2) proper motion, (3) distance (or parallax), and 
     (4) radial velocity.
 CALLING SEQUENCE:
     GAL_UVW, U, V, W, [/LSR, RA=, DEC=, PMRA= ,PMDEC=, VRAD= , DISTANCE= 
              PLX= ]
 OUTPUT PARAMETERS:
      U - Velocity (km/s) positive toward the Galactic *anti*center
      V - Velocity (km/s) positive in the direction of Galactic rotation
      W - Velocity (km/s) positive toward the North Galactic Pole 
 REQUIRED INPUT KEYWORDS:
      User must supply a position, proper motion,radial velocity and distance
      (or parallax).    Either scalars or vectors can be supplied.
     (1) Position:
      RA - Right Ascension in *Degrees*
      Dec - Declination in *Degrees*
     (2) Proper Motion
      PMRA = Proper motion in RA in arc units (typically milli-arcseconds/yr)
            If given mu_alpha --proper motion in seconds of time/year - then
            this is equal to 15*mu_alpha*cos(dec)
      PMDEC = Proper motion in Declination (typically mas/yr)
     (3) Radial Velocity
      VRAD = radial velocity in km/s
     (4) Distance or Parallax
      DISTANCE - distance in parsecs 
                 or
      PLX - parallax with same distance units as proper motion measurements
            typically milliarcseconds (mas)

 OPTIONAL INPUT KEYWORD:
      /LSR - If this keyword is set, then the output velocities will be
             corrected for the solar motion (U,V,W)_Sun = (-8.5, 13.38, 6.49) 
            (Coskunoglu et al. 2011 MNRAS) to the local standard of rest.
            Note that the value of the solar motion through the LSR remains
            poorly determined.
  EXAMPLE:
      (1) Compute the U,V,W coordinates for the halo star HD 6755.  
          Use values from Hipparcos catalog, and correct to the LSR
      ra = ten(1,9,42.3)*15.    & dec = ten(61,32,49.5)
      pmra = 628.42  &  pmdec = 76.65         ;mas/yr
      dis = 139    &  vrad = -321.4
      gal_uvw,u,v,w,ra=ra,dec=dec,pmra=pmra,pmdec=pmdec,vrad=vrad,dis=dis,/lsr
          ===>  u=141.2  v = -491.7  w = 93.9        ;km/s

      (2) Use the Hipparcos Input and Output Catalog IDL databases (see 
      http://idlastro.gsfc.nasa.gov/ftp/zdbase/) to obtain space velocities
      for all stars within 10 pc with radial velocities > 10 km/s

      dbopen,'hipp_new,hic'      ;Need Hipparcos output and input catalogs
      list = dbfind('plx>100,vrad>10')      ;Plx > 100 mas, Vrad > 10 km/s
      dbext,list,'pmra,pmdec,vrad,ra,dec,plx',pmra,pmdec,vrad,ra,dec,plx
      ra = ra*15.                 ;Need right ascension in degrees
      GAL_UVW,u,v,w,ra=ra,dec=dec,pmra=pmra,pmdec=pmdec,vrad=vrad,plx = plx 
      forprint,u,v,w              ;Display results
 METHOD:
      Follows the general outline of Johnson & Soderblom (1987, AJ, 93,864)
      except that U is positive outward toward the Galactic *anti*center, and 
      the J2000 transformation matrix to Galactic coordinates is taken from  
      the introduction to the Hipparcos catalog.   
 REVISION HISTORY:
      Written, W. Landsman                       December   2000
      fix the bug occuring if the input arrays are longer than 32767
        and update the Sun velocity           Sergey Koposov June 2008
	   vectorization of the loop -- performance on large arrays 
        is now 10 times higher                Sergey Koposov December 2008
      More recent value of solar motion WL/SK   Jan 2011

(See $IDLUTILS_DIR/goddard/pro/astro/gal_uvw.pro)

GAUSSIAN

 NAME:
       GAUSSIAN
 PURPOSE:
       Compute the 1-d Gaussian function and optionally the derivative
 EXPLANATION:
       Compute the 1-D Gaussian function and optionally the derivative 
       at an array of points.

 CALLING SEQUENCE:
       y = gaussian( xi, parms,[ pderiv ])

 INPUTS:
       xi = array, independent variable of Gaussian function.

       parms = parameters of Gaussian, 2, 3 or 4 element array:
               parms[0] = maximum value (factor) of Gaussian,
               parms[1] = mean value (center) of Gaussian,
               parms[2] = standard deviation (sigma) of Gaussian.
               (if parms has only 2 elements then sigma taken from previous
               call to gaussian(), which is stored in a  common block).
               parms[3] = optional, constant offset added to Gaussian.
 OUTPUT:
       y -  Function returns array of Gaussian evaluated at xi.    Values will
            be floating pt. (even if xi is double) unless the /DOUBLE keyword
            is set.

 OPTIONAL INPUT:
       /DOUBLE - set this keyword to return double precision for both
             the function values and (optionally) the partial derivatives.
 OPTIONAL OUTPUT:
       pderiv = [N,3] or [N,4] output array of partial derivatives,
               computed only if parameter is present in call.

               pderiv[*,i] = partial derivative at all xi absisca values
               with respect to parms[i], i=0,1,2,[3].


 EXAMPLE:
       Evaulate a Gaussian centered at x=0, with sigma=1, and a peak value
       of 10 at the points 0.5 and 1.5.   Also compute the derivative

       IDL> f = gaussian( [0.5,1.5], [10,0,1], DERIV )
       ==> f= [8.825,3.25].   DERIV will be a 2 x 3 array containing the
       numerical derivative at the two points with respect to the 3 parameters.
 
 COMMON BLOCKS:
       None
 HISTORY:
       Written, Frank Varosi NASA/GSFC 1992.
       Converted to IDL V5.0   W. Landsman   September 1997
       Use machar() for machine precision, added /DOUBLE keyword,
       add optional constant 4th parameter    W. Landsman   November 2001

(See $IDLUTILS_DIR/goddard/pro/math/gaussian.pro)

GCIRC

 NAME:
     GCIRC
 PURPOSE:
     Computes rigorous great circle arc distances.  
 EXPLANATION:
     Input position can either be either radians, sexigesimal RA, Dec or
     degrees.   All computations are double precision. 

 CALLING SEQUENCE:
      GCIRC, U, RA1, DC1, RA2, DC2, DIS

 INPUTS:
      U    -- integer = 0,1, or 2: Describes units of inputs and output:
              0:  everything radians
              1:  RAx in decimal hours, DCx in decimal
                       degrees, DIS in arc seconds 
              2:  RAx and DCx in degrees, DIS in arc seconds
      RA1  -- Right ascension or longitude of point 1
      DC1  -- Declination or latitude of point 1
      RA2  -- Right ascension or longitude of point 2
      DC2  -- Declination or latitude of point 2

 OUTPUTS:
      DIS  -- Angular distance on the sky between points 1 and 2
              See U above for units;  double precision  

 PROCEDURE:
      "Haversine formula" see 
      http://en.wikipedia.org/wiki/Great-circle_distance

 NOTES:
       (1) If RA1,DC1 are scalars, and RA2,DC2 are vectors, then DIS is a
       vector giving the distance of each element of RA2,DC2 to RA1,DC1.
       Similarly, if RA1,DC1 are vectors, and RA2, DC2 are scalars, then DIS
       is a vector giving the distance of each element of RA1, DC1 to 
       RA2, DC2.    If both RA1,DC1 and RA2,DC2 are vectors then DIS is a
       vector giving the distance of each element of RA1,DC1 to the 
       corresponding element of RA2,DC2.    If the input vectors are not the 
       same length, then excess elements of the longer ones will be ignored.

       (2) The function SPHDIST provides an alternate method of computing
        a spherical distance.

       (3) The haversine formula can give rounding errors for antipodal
       points.

 PROCEDURE CALLS:
      None

   MODIFICATION HISTORY:
      Written in Fortran by R. Hill -- SASC Technologies -- January 3, 1986
      Translated from FORTRAN to IDL, RSH, STX, 2/6/87
      Vector arguments allowed    W. Landsman    April 1989
      Prints result if last argument not given.  RSH, RSTX, 3 Apr. 1998
      Remove ISARRAY(), V5.1 version        W. Landsman   August 2000
      Added option U=2                      W. Landsman   October 2006
      Use double precision for U=0 as advertised R. McMahon/W.L.  April 2007
      Use havesine formula, which has less roundoff error in the 
             milliarcsecond regime      W.L. Mar 2009

(See $IDLUTILS_DIR/goddard/pro/astro/gcirc.pro)

GCNTRD

  NAME: 
       GCNTRD
  PURPOSE:
       Compute the stellar centroid by Gaussian fits to marginal X,Y, sums 
 EXPLANATION:
       GCNTRD uses the DAOPHOT "FIND" centroid algorithm by fitting Gaussians
       to the marginal X,Y distributions.     User can specify bad pixels 
       (either by using the MAXGOOD keyword or setting them to NaN) to be
       ignored in the fit.    Pixel values are weighted toward the center to
       avoid contamination by neighboring stars. 

  CALLING SEQUENCE: 
       GCNTRD, img, x, y, xcen, ycen, [ fwhm , /SILENT, /DEBUG, MAXGOOD = ,
                            /KEEPCENTER ]

  INPUTS:     
       IMG - Two dimensional image array
       X,Y - Scalar or vector integers giving approximate stellar center

  OPTIONAL INPUT:
       FWHM - floating scalar; Centroid is computed using a box of half
               width equal to 1.5 sigma = 0.637* FWHM.  GCNTRD will prompt
               for FWHM if not supplied

  OUTPUTS:   
       XCEN - the computed X centroid position, same number of points as X
       YCEN - computed Y centroid position, same number of points as Y

       Values for XCEN and YCEN will not be computed if the computed
       centroid falls outside of the box, or if there are too many bad pixels,
       or if the best-fit Gaussian has a negative height.   If the centroid 
       cannot be computed, then a  message is displayed (unless /SILENT is 
       set) and XCEN and YCEN are set to -1.

  OPTIONAL OUTPUT KEYWORDS:
       MAXGOOD=  Only pixels with values less than MAXGOOD are used to in
               Gaussian fits to determine the centroid.    For non-integer
               data, one can also flag bad pixels using NaN values.
       /SILENT - Normally GCNTRD prints an error message if it is unable
               to compute the centroid.   Set /SILENT to suppress this.
       /DEBUG - If this keyword is set, then GCNTRD will display the subarray
               it is using to compute the centroid.
       /KeepCenter  By default, GCNTRD first convolves a small region around 
              the supplied position with a lowered Gaussian filter, and then 
              finds the maximum pixel in a box centered on the input X,Y 
              coordinates, and then extracts a new box about this maximum 
              pixel.   Set the /KeepCenter keyword  to skip the convolution 
              and finding the maximum pixel, and instead use a box 
              centered on the input X,Y coordinates.                          
  PROCEDURE: 
       Unless /KEEPCENTER is set, a small area around the initial X,Y is 
       convolved with a Gaussian kernel, and the maximum pixel is found.
       This pixel is used as the  center of a square, within 
       which the centroid is computed as the Gaussian least-squares fit
       to the  marginal sums in the X and Y directions. 

  EXAMPLE:
       Find the centroid of a star in an image im, with approximate center
       631, 48.    Assume that bad (saturated) pixels have a value of 4096 or
       or higher, and that the approximate FWHM is 3 pixels.

       IDL> GCNTRD, IM, 631, 48, XCEN, YCEN, 3, MAXGOOD = 4096       
  MODIFICATION HISTORY:
       Written June 2004, W. Landsman  following algorithm used by P. Stetson 
             in DAOPHOT2.
       Modified centroid computation (as in IRAF/DAOFIND) to allow shifts of
      more than 1 pixel from initial guess.    March 2008
      First perform Gaussian convolution prior to finding maximum pixel 
      to smooth out noise  W. Landsman  Jan 2009

(See $IDLUTILS_DIR/goddard/pro/idlphot/gcntrd.pro)

GEO2ECI

 NAME:
     GEO2ECI

 PURPOSE:
     Convert geographic spherical coordinates to Earth-centered inertial coords

 EXPLANATION:
     Converts from geographic spherical coordinates [latitude, longitude, 
     altitude] to ECI (Earth-Centered Inertial) [X,Y,Z] rectangular 
     coordinates.    JD time is also needed.

     Geographic coordinates are in degrees/degrees/km
     Geographic coordinates assume the Earth is a perfect sphere, with radius 
       equal to its equatorial radius.
     ECI coordinates are in km from Earth center.

 CALLING SEQUENCE:
       ECIcoord=geo2eci(gcoord,JDtime)

 INPUT:
       gcoord: geographic [latitude,longitude,altitude], or a an array [3,n] 
                of n such coordinates
       JDtime: Julian Day time, double precision. Can be a 1-D array of n 
               such times.

 KEYWORD INPUTS:
       None

 OUTPUT:
       a 3-element array of ECI [X,Y,Z] coordinates, or an array [3,n] of 
                n such coordinates, double precision   
       
 COMMON BLOCKS:
       None

 PROCEDURES USED:
       CT2LST - Convert Local Civil Time to Local Mean Sidereal Time

 EXAMPLES:

       IDL> ECIcoord=geo2eci([0,0,0], 2452343.38982663D)
       IDL> print,ECIcoord
      -3902.9606       5044.5548       0.0000000

       (The above is the ECI coordinates of the intersection of the equator and
       Greenwich's meridian on 2002/03/09 21:21:21.021)

 MODIFICATION HISTORY:
       Written by Pascal Saint-Hilaire (shilaire@astro.phys.ethz.ch) 
             on 2002/05/14

(See $IDLUTILS_DIR/goddard/pro/astro/geo2eci.pro)

GEO2GEODETIC

 NAME:
       GEO2GEODETIC

 PURPOSE:
       Convert from geographic/planetographic to geodetic coordinates
 EXPLANATION:
       Converts from geographic (latitude, longitude, altitude) to geodetic
       (latitude, longitude, altitude).  In geographic coordinates, the 
           Earth is assumed a perfect sphere with a radius equal to its equatorial 
               radius. The geodetic (or ellipsoidal) coordinate system takes into 
               account the Earth's oblateness.

       Geographic and geodetic longitudes are identical.
               Geodetic latitude is the angle between local zenith and the equatorial plane.
               Geographic and geodetic altitudes are both the closest distance between 
               the satellite and the ground.

       The PLANET keyword allows a similar transformation for the other 
       planets  (planetographic to planetodetic coordinates). 

       The EQUATORIAL_RADIUS and POLAR_RADIUS keywords allow the 
       transformation for any ellipsoid.

       Latitudes and longitudes are expressed in degrees, altitudes in km.

       REF: Stephen P.  Keeler and Yves Nievergelt, "Computing geodetic
       coordinates", SIAM Rev. Vol. 40, No. 2, pp. 300-309, June 1998

       Planetary constants from "Allen's Astrophysical Quantities", 
       Fourth Ed., (2000)

 CALLING SEQUENCE:
       ecoord=geo2geodetic(gcoord,[ PLANET=,EQUATORIAL_RADIUS=, POLAR_RADIUS=])

 INPUT:
       gcoord = a 3-element array of geographic [latitude,longitude,altitude],
                or an array [3,n] of n such coordinates.


 OPTIONAL KEYWORD INPUT:
       PLANET = keyword specifying planet (default is Earth).   The planet
                may be specified either as an integer (1-9) or as one of the
                (case-independent) strings 'mercury','venus','earth','mars',
                'jupiter','saturn','uranus','neptune', or 'pluto'
               
       EQUATORIAL_RADIUS : Self-explanatory. In km. If not set, PLANET's 
                value is used.
       POLAR_RADIUS : Self-explanatory. In km. If not set, PLANET's value is 
                used.

 OUTPUT:
      a 3-element array of geodetic/planetodetic [latitude,longitude,altitude],
        or an array [3,n] of n such coordinates, double precision.

 COMMON BLOCKS:
       None

 RESTRICTIONS:

       Whereas the conversion from geodetic to geographic coordinates is given
       by an exact, analytical formula, the conversion from geographic to
       geodetic isn't. Approximative iterations (as used here) exist, but tend 
       to become less good with increasing eccentricity and altitude.
       The formula used in this routine should give correct results within
       six digits for all spatial locations, for an ellipsoid (planet) with
       an eccentricity similar to or less than Earth's.
       More accurate results can be obtained via calculus, needing a 
       non-determined amount of iterations.
       In any case, 
          IDL> PRINT,geodetic2geo(geo2geodetic(gcoord)) - gcoord
       is a pretty good way to evaluate the accuracy of geo2geodetic.pro.

 EXAMPLES:

       Locate the geographic North pole, altitude 0., in geodetic coordinates
       IDL> geo=[90.d0,0.d0,0.d0]  
       IDL> geod=geo2geodetic(geo); convert to equivalent geodetic coordinates
       IDL> PRINT,geod
       90.000000       0.0000000       21.385000

       As above, but for the case of Mars
       IDL> geod=geo2geodetic(geo,PLANET='Mars')
       IDL> PRINT,geod
       90.000000       0.0000000       18.235500

 MODIFICATION HISTORY:
       Written by Pascal Saint-Hilaire (shilaire@astro.phys.ethz.ch), May 2002
       Generalized for all solar system planets by Robert L. Marcialis
               (umpire@lpl.arizona.edu), May 2002
       Modified 2002/05/18, PSH: added keywords EQUATORIAL_RADIUS and 
               POLAR_RADIUS

(See $IDLUTILS_DIR/goddard/pro/astro/geo2geodetic.pro)

GEO2MAG()

 NAME:
       GEO2MAG()

 PURPOSE:
       Convert from geographic to geomagnetic coordinates
 EXPLANATION:
       Converts from GEOGRAPHIC (latitude,longitude) to GEOMAGNETIC (latitude, 
       longitude).   (Altitude remains the same)

       Latitudes and longitudes are expressed in degrees.

 CALLING SEQUENCE:
       mcoord=geo2mag(gcoord)

 INPUT:
       gcoord = a 2-element array of geographic [latitude,longitude], or an 
                array [2,n] of n such coordinates.

 KEYWORD INPUTS:
       None

 OUTPUT:
       a 2-element array of magnetic [latitude,longitude], or an array [2,n] 
         of n such coordinates                     

 COMMON BLOCKS:
       None

 EXAMPLES:
       geographic coordinates of magnetic south pole

       IDL> mcoord=geo2mag([79.3,288.59])      
       IDL> print,mcoord
       89.999992      -173.02325

 MODIFICATION HISTORY:
       Written by Pascal Saint-Hilaire (Saint-Hilaire@astro.phys.ethz.ch), 
            May 2002

(See $IDLUTILS_DIR/goddard/pro/astro/geo2mag.pro)

GEODETIC2GEO

 NAME:
       GEODETIC2GEO

 PURPOSE:
       Convert from geodetic (or planetodetic) to geographic coordinates
 EXPLANATION:
       Converts from geodetic (latitude, longitude, altitude) to geographic
       (latitude, longitude, altitude).  In geographic coordinates, the 
       Earth is assumed a perfect sphere with a radius equal to its equatorial 
       radius. The geodetic (or ellipsoidal) coordinate system takes into 
       account the Earth's oblateness.

       Geographic and geodetic longitudes are identical.
       Geodetic latitude is the angle between local zenith and the equatorial 
       plane.   Geographic and geodetic altitudes are both the closest distance
       between the satellite and the ground.

       The PLANET keyword allows a similar transformation for the other 
       planets  (planetodetic to planetographic coordinates). 

       The EQUATORIAL_RADIUS and POLAR_RADIUS keywords allow the 
       transformation for any ellipsoid.

       Latitudes and longitudes are expressed in degrees, altitudes in km.

       REF: Stephen P.  Keeler and Yves Nievergelt, "Computing geodetic
       coordinates", SIAM Rev. Vol. 40, No. 2, pp. 300-309, June 1998
       Planetary constants from "Allen's Astrophysical Quantities", 
       Fourth Ed., (2000)

 CALLING SEQUENCE:
       gcoord = geodetic2geo(ecoord, [ PLANET= ] )

 INPUT:
       ecoord = a 3-element array of geodetic [latitude,longitude,altitude],
                or an array [3,n] of n such coordinates.

 OPTIONAL KEYWORD INPUT:
       PLANET = keyword specifying planet (default is Earth).   The planet
                may be specified either as an integer (1-9) or as one of the
                (case-independent) strings 'mercury','venus','earth','mars',
                'jupiter','saturn','uranus','neptune', or 'pluto'

       EQUATORIAL_RADIUS : Self-explanatory. In km. If not set, PLANET's value
                is used.   Numeric scalar
       POLAR_RADIUS : Self-explanatory. In km. If not set, PLANET's value is 
                 used.   Numeric scalar

 OUTPUT:
       a 3-element array of geographic [latitude,longitude,altitude], or an
         array [3,n] of n such coordinates, double precision

       The geographic and geodetic longitudes will be identical.
 COMMON BLOCKS:
       None

 EXAMPLES:

       IDL> geod=[90,0,0]  ; North pole, altitude 0., in geodetic coordinates
       IDL> geo=geodetic2geo(geod)
       IDL> PRINT,geo
       90.000000       0.0000000      -21.385000

       As above, but the equivalent planetographic coordinates for Mars
       IDL> geod=geodetic2geo(geod,PLANET='Mars'); 
       IDL> PRINT,geod
       90.000000       0.0000000      -18.235500

 MODIFICATION HISTORY:
       Written by Pascal Saint-Hilaire (shilaire@astro.phys.ethz.ch),
                  May 2002

       Generalized for all solar system planets by Robert L. Marcialis
               (umpire@lpl.arizona.edu), May 2002

       Modified 2002/05/18, PSH: added keywords EQUATORIAL_RADIUS and 
                POLAR_RADIUS

(See $IDLUTILS_DIR/goddard/pro/astro/geodetic2geo.pro)

GETDECOMPOSEDSTATE

  Provides a device-independent way to get the color decomposition state of the
  current graphics device. 

 :Categories:
    Graphics, Utilities
    
 :Returns:
     Returns a 1 if color decomposition is turned on and a 0 if indexed color is used.
       
 :Keywords:
     Depth: out, optional, type=integer
         The depth of the color display. Typically 8 for indexed color devices
         and 24 for true-color devices.
          
 :Examples:
       IDL> currentState = GetDecomposedState()
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 12 December 2010 as a better named wrapper for DECOMPOSEDCOLOR program. DWF.

 :Copyright:
     Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/getdecomposedstate.pro)

GETOPT

 NAME:
	GETOPT
 PURPOSE:
	Convert a string supplied by the user into a valid scalar or vector
 EXPLANATION:
	Distinct elements in the string may be
	separated by either a comma or a space.  The output scalar
	or vector can be specified to be  either  integer or floating
	point.   A null string is converted to a zero.   
 CALLING SEQUENCE:
     option = GETOPT( input, [ type, numopt, COUNT = ])

 INPUTS:
	input   - string that was input by user in response to a prompt
		Arithmetic operations can be included in the string (see
		examples)

 OPTIONAL INPUTS:
	type    - Either an "I" (integer) or an "F" (floating point) specifying 
		the datatype of the output vector.  Default is floating point

	numopt  - number of values expected by calling procedure
		If less than NUMOPT values are supplied the output
		vector will be padded with zeros.  
 OUTPUTS:
	option  - scalar or vector containing the numeric conversion of
		the fields in the string INPUT.  If NUMOPT is not
		supplied, the number of elements in OPTION will 
		equal the number of distinct fields in INPUT.
 OPTIONAL INPUT KEYWORD:
       Count - integer giving the number of values actually returned by
               GETOPT.   If the input is invalid then COUNT is set to -1
 NOTES:
	(1) If an input is invalid, Count is set to -1 and the result is set 
		to 999.
	(2) GETOPT uses the execute function to interpret the user string.   
	 	Therefore GETOPT itself cannot be called with the EXECUTE 
		function.
	(3) GETOPT has a hard limit of 10 tokens in the input string. 

 EXAMPLES:
	(1)   a = getopt( '3.4,5*4 ', 'I' )    yields   a = [ 3, 20]
	(2)   a = getopt( '5/2.', 'F', 5)      yields   a = [2.5,0.,0.,0.,0.]
	(3)   a = getopt( '2*3,5,6')           yields   a = [6.,5.,6.]

 REVISON HISTORY:
	written by B. Pfarr, STX, 5/6/87
	change value of !ERR W. Landsman   STX,  6/30/88
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/getopt.pro)

GETPRIMARYSCREENSIZE

 :Description:
   Provides a way to get the screen size of the primary monitor, especially when
   there are several being used.

 :Categories:
    Graphics
    
 :Params:
    none 
       
 :Keywords:
     exclude_taskbar: in, optional, boolean, default=0
         Set this keyword to exclude the taskbar from the monitor size.
         This keyword is ignored on all but Windows machines.
          
 :Author:
       Dick Jackson, www.dick-jackson.com
       
 :History:
     Change History::
        Written, 8 March 2011. DJ
        Modified to only use IDLsysMonitorInfo for IDL 6.3 and higher. 23 Feb 2012. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/getprimaryscreensize.pro)

GETPRO

 NAME:
     GETPRO
 PURPOSE:
     Search !PATH for a procedure, and copy into user's working directory
 EXPLANATION:
     Extract a procedure from an IDL Library or directory given in the 
     !PATH  system variable and place it in the current default directory
     (presumably to be edited by the user). 

 CALLING SEQUENCE:
     GETPRO, [ proc_name ]          ;Find PROC_NAME in !PATH and copy

 OPTIONAL INPUT:
     proc_name - Character string giving the name of the IDL procedure or 
               function.  Do not give an extension.   If omitted, 
               the program will prompt for PROC_NAME.   

 OUTPUTS:
     None.

 SIDE EFFECTS:
      A file with the extension .pro and a name given by PROC_NAME will
      be created on the user's directory.

 PROCEDURE:
      The FILE_WHICH() function is used to locate the procedure in the IDL
      !PATH.     When found, FILE_COPY is used to 
      copy the procedure into the user's current default directory.    If not 
      found in !PATH, then the ROUTINE_INFO() function is used to determine 
      if it is an intrinsic IDL procedure.  

 EXAMPLE:
       Put a copy of the USER library procedure CURVEFIT on the current
       directory

       IDL> getpro, 'CURVEFIT'

 RESTRICTIONS:
       User will be unable to obain source code for a native IDL function
       or procedure, or for a FORTRAN or C routine added with CALL_EXTERNAL.
       User must have write privilege to the current directory

 PROCEDURE CALLS:
      ZPARCHECK
 REVISION HISTORY:
      Written W. Landsman, STX Corp.   June 1990
      Now use intrinsic EXPAND_PATH() command  W. Landsman November 1994
      Use ROUTINE_NAMES() to check for intrinsic procs  W. Landsman July 95
      Update for Windows/IDL     W. Landsman      September 95
      Check if procedure is in current directory  W. Landsman  June 1997
      Use ROUTINE_INFO instead of undocumented ROUTINE_NAMES W.L. October 1998
      Use FILE_WHICH() to locate procedure W. Landsman May 2006 
      Assume since V5.5, remove VMS support  W. Landsman Sep 2006
      Assume since V6.0, use file_basename() W.Landsman Feb 2009
      Test for .sav file, more robust test for write privilege W.L. Jul 2010

(See $IDLUTILS_DIR/goddard/pro/misc/getpro.pro)

GETPSF

 NAME:
	GETPSF
 PURPOSE:
	To generate a point-spread function (PSF) from observed stars. 
 EXPLANATION:
	The PSF is represented as a 2-dimensional Gaussian
	(integrated over each pixel) and a lookup table of residuals.
	The lookup table and Gaussian parameters are output in a FITS
	image file.   The PSF FITS file created by GETPSF can be
	read with the procedure RDPSF.      Adapted from the 1986 STSDAS 
	version of DAOPHOT

 CALLING SEQUENCE:
	GETPSF, image, xc, yc, apmag, sky, [ronois, phpadu, gauss, psf, 
			idpsf, psfrad, fitrad, psfname, /DEBUG ]

 INPUTS:
	IMAGE  - input image array
	XC     - input vector of x coordinates (from FIND), these should be
		IDL (first pixel is (0,0)) convention.
	YC     - input vector of y coordinates (from FIND)
	APMAG  - vector of magnitudes (from APER), used for initial estimate
		of gaussian intensity.  If APMAG is multidimensional, (more
		than 1 aperture was used in APER) then the first aperture
		is used.
	SKY    - vector of sky values (from APER)                

 OPTIONAL INPUTS:
	The user will be prompted for the following parameters if not supplied.

	RONOIS - readout noise per pixel, (in electrons, or equivalent photons)
	PHPADU - photons per analog digital unit, used to scale the data
		numbers in IMAGE into photon units
	IDPSF  - subscripts of the list of stars created by 
		APER which will be used to define the PSF.   Stars whose
		centroid does not fall within PSFRAD of the edge of the frame,
		or for which a Gaussian fit requires more than 25 iterations,
		will be ignored when creating the final PSF.
	PSFRAD - the scalar radius, in pixels, of the circular area within
		which the PSF will be defined.   This should be slightly larger
		than the radius of the brightest star that one will be
		interested in.
	FITRAD - the scalar radius, in pixels of the circular area used in the
		least-square star fits.  Stetson suggest that FITRAD should
		approximately equal to the FWHM, slightly less for crowded
		fields.  (FITRAD must be smaller than PSFRAD.)
	PSFNAME- Name of the FITS file that will contain the table of residuals,
		and the best-fit Gaussian parameters.    This file is 
		subsequently required for use by NSTAR.  

 OPTIONAL OUTPUTS:
	GAUSS  - 5 element vector giving parameters of gaussian fit to the 
		first PSF star
		GAUSS(0) - height of the gaussian (above sky)
		GAUSS(1) - the offset (in pixels) of the best fitting gaussian
			and the original X centroid
		GAUSS(2) - similiar offset from the Y centroid 
		GAUSS(3) - Gaussian sigma in X
		GAUSS(4) - Gaussian sigma in Y
	PSF    - 2-d array of PSF residuals after a Gaussian fit.

 PROCEDURE:
	GETPSF fits a Gaussian profile to the core of the first PSF star 
	and generates a look-up table of the residuals of the
	actual image data from the Gaussian fit.  If desired, it will then
	fit this PSF to another star (using PKFIT) to determine its precise 
	centroid, scale the same Gaussian to the new star's core, and add the
	differences between the actual data and the scaled Gaussian to the
	table of residuals.   (In other words, the Gaussian fit is performed
       only on the first star.)

 OPTIONAL KEYWORD INPUT:
	DEBUG - if this keyword is set and non-zero, then the result of each
		fitting iteration will be displayed.

 PROCEDURES CALLED
	DAOERF, MAKE_2D, MKHDR, RINTER(), PKFIT, STRNUMBER(), STRN(), WRITEFITS

 REVISON HISTORY:
	Adapted from the 1986 version of DAOPHOT in STSDAS
	IDL Version 2  W Landsman           November 1988
	Use DEBUG keyword instead of !DEBUG  W. Landsman       May 1996
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/idlphot/getpsf.pro)

GETROT

 NAME:
    GETROT
 PURPOSE:
     Return the rotation and plate scale of an image from its FITS header
 EXPLANATION:
     Derive the counterclockwise rotation angle, and the X and Y scale
     factors of an image, from a FITS image header.   The input parameter 
     may be either a FITS image header or an astrometry structure (as 
     obtained by extast.pro)

 CALLING SEQUENCE:
     GETROT, Hdr, [ Rot, CDelt, /SILENT, DEBUG =  ]   
             or 
     GETROT, Astr, Rot, CDelt, /SILENT, DEBUG = ]       

 INPUT PARAMETERS:
     HDR - FITS Image header (string array).  Program will extract the 
             astrometry structure
              or
     ASTR -  ASTROMETRY structure, of the type returned by EXTAST.
             See the documentation for EXTAST.PRO for details.

 OPTIONAL OUTPUT PARAMETERS:
       ROT - Scalar giving the counterclockwise rotation of NORTH in DEGREES 
               from the +Y axis of the image.
       CDELT- 2 element vector giving the scale factors in DEGREES/PIXEL in 
               the X and Y directions.   CDELT[1] is always positive, whereas
               CDELT[0] is negative for a normal left-handed coordinate system,
               and positive for a right-handed system. 

       If no output variables are supplied (or /DEBUG is set), then GETROT 
       will display the rotation and plate scale at the terminal.

 OPTIONAL INPUT KEYWORD
 
       ALT - single character 'A' through 'Z' or ' ' specifying an alternate
             astrometry system present in the FITS header.   See extast.pro
             for more information on the ALT keyword.    Ignored if an
             astrometry structure rather than FITS header is supplied.
       DEBUG - if DEBUG is set, GETROT will print the rotation for both the 
           X and Y axis when these values are unequal.  If DEBUG is set to 2, 
           then the output parameter ROT will contain both X and Y rotations.

       /SILENT - if set, then do not provide a warning about a right-handed
           coordinate system
 PROCEDURE:
       If the FITS header already contains CDELT (and CD or CROTA) keyword,
       (as suggested by the Calabretta & Greisen (2002, A&A, 395, 1077) FITS 
       standard) then this is used for the scale factor.
       
       If the header contains CD keywords but no CDELT keywords (as in IRAF
       headers) then the scale factor is derived from the CD matrix.

       In case of skew (different rotations of the X and Y axes), the rotations
       are averaged together if they are less than 2 degrees.   Otherwise,
       a warning is given and the X rotation is used.  

 PROCEDURES USED:
       EXTAST, GSSS_EXTAST
 REVISION HISTORY:
       Written W. Landsman STX January 1987 
       Option to return both rotations added.  J. D. Offenberg, STX, Aug 1991
       Use new astrometry structure   W. Landsman  Mar 1994
       Recognize a GSSS header        W. Landsman  June 1994
       Correct rotation determination with unequal CDELT values WL October 1998
       Consistent conversion between CROTA and CD matrix  WL  October 2000
       Correct CDELT computations for rotations near 90 deg WL November 2002
       Preserve sign in the CDELT output  WL June 2003
       Check if latitude/longitude reversed in CTYPE  WL  February 2004
       Fix problem in latitude check  M.Lombardi/W.Landsman Sep 2004
       Added ALT keyword W. Landsman May 2005
       Account for any rotation of the native system by examining the value
        of LONGPOLE       H. Taylor/W. Landsman
       Account for case where X,Y rotations differ by 2*!pi WL. Aug 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/getrot.pro)

GETTOK

 NAME:
	GETTOK                                    
 PURPOSE:
	Retrieve the first part of a (vector) string up to a specified character
 EXPLANATION:
	GET TOKen - Retrieve first part of string until the character char 
	is encountered.   

 CALLING SEQUENCE:
	token = gettok( st, char, [ /EXACT, /NOTRIM ] )

 INPUT:
	char - character separating tokens, scalar string

 INPUT-OUTPUT:
	st - string to get token from (on output token is removed unless
            /NOTRIM is set), scalar or vector

 OUTPUT:
	token - extracted string value is returned, same dimensions as st
 OPTIONAL INPUT KEYWORD:
       /EXACT -  The default behaviour of GETTOK is to remove any leading 
              blanks and (if the token is a blank) convert tabs to blanks.    
              Set the /EXACT keyword to skip these steps and leave the 
              input string unchanged before searching for the  character 
              tokens. 

      /NOTRIM - if set, then the input string is left unaltered 
 EXAMPLE:
	If ST is ['abc=999','x=3.4234'] then gettok(ST,'=') would return
	['abc','x'] and ST would be left as ['999','3.4234'] 

 PROCEDURE CALLS:
       REPCHR()
 HISTORY
	version 1  by D. Lindler APR,86
	Remove leading blanks    W. Landsman (from JKF)    Aug. 1991
       V5.3 version, accept vector input   W. Landsman February 2000
       Slightly faster implementation  W. Landsman   February 2001
       Added EXACT keyword  W. Landsman March 2004
       Assume since V5.4, Use COMPLEMENT keyword to WHERE W. Landsman Apr 2006
       Added NOTRIM keyword W. L. March 2011

(See $IDLUTILS_DIR/goddard/pro/misc/gettok.pro)

GETWRD

 NAME:
       GETWRD
 PURPOSE:
       Return the n'th word from a text string.
 CATEGORY:
 CALLING SEQUENCE:
       wrd = getwrd(txt, n, [m])
 INPUTS:
       txt = text string to extract from.         in
         The first element is used if txt is an array.
       n = word number to get (first = 0 = def).  in
       m = optional last word number to get.      in
 KEYWORD PARAMETERS:
       Keywords:
         LOCATION = l.  Return word n string location.
         DELIMITER = d. Set word delimiter (def = space & tab).
         /LAST means n is offset from last word.  So n=0 gives
           last word, n=-1 gives next to last, ...
           If n=-2 and m=0 then last 3 words are returned.
         /NOTRIM suppresses whitespace trimming on ends.
         NWORDS=n.  Returns number of words in string.
 OUTPUTS:
       wrd = returned word or words.              out
 COMMON BLOCKS:
       getwrd_com
 NOTES:
       Note: If a NULL string is given (txt="") then the last string
             given is used.  This saves finding the words again.
             If m > n wrd will be a string of words from word n to
             word m.  If no m is given wrd will be a single word.
             n<0 returns text starting at word abs(n) to string end
             If n is out of range then a null string is returned.
             See also nwrds.
 MODIFICATION HISTORY:
       Ray Sterner,  6 Jan, 1985.
       R. Sterner, Fall 1989 --- converted to SUN.
       R. Sterner, Jan 1990 --- added delimiter.
       R. Sterner, 18 Mar, 1990 --- added /LAST.
       R. Sterner, 31 Jan, 1991 --- added /NOTRIM.
       R. Sterner, 20 May, 1991 --- Added common and NULL string.
       R. Sterner, 13 Dec, 1992 --- Made tabs equivalent to spaces.
       R. Sterner,  4 Jan, 1993 --- Added NWORDS keyword.
       R. Sterner, 2001 Jan 15 --- Fixed to use first element if not a scalar.
       Johns Hopkins University Applied Physics Laboratory.

 Copyright (C) 1985, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.

(See $IDLUTILS_DIR/goddard/pro/jhuapl/getwrd.pro)

GET_COORDS

 NAME:
       GET_COORDS

 PURPOSE:
       Converts a string with angular coordinates  to floating point values.  
 EXPLANATION:
       Although called by ASTRO.PRO, this is a general purpose routine.
       The user may input as floating point or sexigesimal.  If user inputs 
       calling procedure's job to convert hours to degrees if needed.
       Since the input string is parsed character-by-character, ANY character
       that is not a digit, minus sign or decimal point may be used as a 
       delimiter, i.e. acceptable examples of user input are:

       1:03:55 -10:15:31
       1 3 55.0 -10 15 31
       1*3 55              -10abcd15efghij31
       1.065278  hello   -10.25861

 CALLING SEQUENCE:
       GET_COORDS, Coords, [ PromptString, NumVals, INSTRING =, /QUIET ]

 OPTIONAL INPUT:
       PromptString - A string to inform the user what data are to be entered

 OPTIONAL KEYWORD INPUT:
       InString - a keyword that, if set, is assumed to already contain the
               input data string to be parsed.  If this keyword is set, then
               the user is not prompted for any input.
       /Quiet - if set the program won't printout any error messages, but bad
               input is still flagged by Coords=[-999,-999].

 OUTPUT:
       Coords - a 2 element floating array containing the coordinates.  The
               vector [-999,-999] is returned if there has been an error.

 OPTIONAL OUTPUT:
       NumVals - the number of separate values entered by the user:  2 if the
               user entered the coordinates as floating point numbers, 6 if 
               the user entered the coordinates as sexigesimal numbers.  Some
               calling procedures might find this information useful (e.g., to
               to print some output in the same format as the user's input).

 REVISION HISTORY:
       Written by Joel Parker, 5 MAR 90
       Included InString and Quiet keywords.  Cleaned up some of the code and
       comments.  JWmP,  16 Jun 94

*******************************************************************************
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/get_coords.pro)

GET_DATE

 NAME:
       GET_DATE
 PURPOSE:
       Return the (current) UTC date in CCYY-MM-DD format for FITS headers
 EXPLANATION:
       This is the format required by the DATE and DATE-OBS keywords in a 
       FITS header.  

 CALLING SEQUENCE:
       GET_DATE, FITS_date, [ in_date, /OLD, /TIMETAG ]
 OPTIONAL INPUTS:
       in_date - string (scalar or vector) containing dates in IDL
            systime() format (e.g. 'Tue Sep 25 14:56:14 2001')
 OUTPUTS:
       FITS_date = A scalar character string giving the current date.    Actual
               appearance of dte depends on which keywords are supplied.
       
       No Keywords supplied - dte is a 10 character string with the format
               CCYY-MM-DD where <CCYY> represents a calendar year, <MM> the
               ordinal number of a calendar month within the calendar year, 
               and <DD> the ordinal number of a day within the calendar month.
       /TIMETAG set - dte is a 19 character string with the format
               CCYY-MM-DDThh:mm:ss where <hh> represents the hour in the day,
                <mm> the minutes, <ss> the seconds, and the literal 'T' the 
               ISO 8601 time designator
       /OLD set - dte is an 8 character string in DD/MM/YY format

 INPUT KEYWORDS:
       /TIMETAG - Specify the time to the nearest second in the DATE format
       /OLD - Return the DATE format formerly (pre-1997) recommended for FITS
               Note that this format is now deprecated because it uses only
               a 2 digit representation of the year. 
 EXAMPLE:
       Add the current date to the DATE keyword in a FITS header,h
     
       IDL> GET_DATE,dte
       IDL> sxaddpar, h, 'DATE', dte, 'Date header was created'

 NOTES:
       (1) A discussion of the DATExxx syntax in FITS headers can be found in
       http://www.cv.nrao.edu/fits/documents/standards/year2000.txt

       (2) Those who wish to use need further flexibility in their date 
       formats (e.g. to use TAI time) should look at Bill Thompson's time
       routines in http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/time

 PROCEDURES USED:
       DAYCNV - Convert Julian date to Gregorian calendar date
 REVISION HISTORY:
       Written      W. Landsman          March 1991
       Major rewrite to write new DATExxx syntax  W. Landsman  August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Work after year 2000 even with /OLD keyword W. Landsman January 2000
       Don't need to worry about TIME_DIFF since V5.4 W. Landsman July 2001
       Assume since V5.4, remove LOCAL_DIFF keyword  W. Landsman April 2006

(See $IDLUTILS_DIR/goddard/pro/astro/get_date.pro)

GET_EQUINOX

 NAME:
       GET_EQUINOX
 PURPOSE:
       Return the equinox value from a FITS header.  
 EXPLANATION:
       Checks for 4 possibilities:

       (1)  If the EQUINOX keyword is found and has a numeric value, then this
               value is returned
       (2)  If the EQUINOX keyword has the values 'J2000' or 'B1950', then
               either 2000. or 1950. is returned.
       (3)  If the EQUINOX keyword is not found, then GET_EQUINOX will return
               the EPOCH keyword value.   This usage of EPOCH is disparaged.
       (4)  If neither EQUINOX no EPOCH is found, then the RADESYS keyword 
               (or the deprecated RADECSYS keyword) is checked.   If the value 
               is 'ICRS' or 'FK5' then 2000 is is returned, if it is 'FK4' then
               1950 is returned.

       According Calabretta & Greisen (2002, A&A, 395, 1077) the EQUINOX should
       be written as a numeric value, as in format (1).   However, in older 
       FITS headers, the EQUINOX might have been written using formats (2) or 
       (3).      
 CALLING SEQUENCE:
       Year = GET_EQUINOX( Hdr, [ Code ] )   

 INPUTS:
       Hdr - FITS Header, string array, will be searched for the EQUINOX
               (or EPOCH) keyword.

 OUTPUT:
       Year - Year of equinox in FITS header, numeric scalar
 OPTIONAL OUTPUT:
       Code - Result of header search, scalar
               -1 - EQUINOX, EPOCH or RADECSYS keyword not found in header
               0 - EQUINOX found as a numeric value
               1 - EPOCH keyword used for equinox (not recommended)
               2 - EQUINOX found as  'B1950'
               3 - EQUINOX found as  'J2000'
               4 - EQUINOX derived from value of RADESYS or RADECSYS keyword
                   'ICRS', 'FK5' ==> 2000,  'FK4' ==> 1950
 OPTIONAL KEYWORD INPUT: 
       ALT -  single character 'A' through 'Z' or ' ' specifying which  
             astrometry system to use in the FITS header.    The default is
             to use the primary astrometry or ALT = ''.   If /ALT is set, 
             then this is equivalent to ALT = 'A'.   See Section 3.3 of 
             Greisen & Calabretta (2002, A&A, 395, 1061) for information about
             alternate astrometry keywords.
 PROCEDURES USED:
       ZPARCHECK, SXPAR()  
 NOTES:
       Technically, RADESYS = 'ICRS' does not specify any equinox, but can be 
       assumed to be equivalent to J2000 for all but highest-precision work.      
 REVISION HISTORY:                                               
       Written  W. Landsman        STX              March, 1991
       Don't use !ERR          W. Landsman   February 2000
       N = 1 for check of EPOCH keyword, not 0 S. Ott July 2000
       Added ALT keyword, recognize RADESYS along with deprecated RADECSYS
              W. Landsman   Sep 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/get_equinox.pro)

GET_JULDATE

 NAME:
    GET_JULDATE
 PURPOSE:
     Return the current Julian Date

 EXPLANATION:
     In V5.4, GET_JULDATE became completely obsolete with the introduction
     of the /UTC keyword to SYSTIME().   So GET_JULDATE,jd is equivalent to
     jd = SYSTIME(/JULIAN,/UTC).

 CALLING SEQUENCE:
       GET_JULDATE,jd

 INPUTS:
       None

 OUTPUTS:
       jd = Current Julian Date, double precision scalar

 EXAMPLE:
       Return the current hour, day, month and year as integers

       IDL> GET_JULDATE, JD                  ;Get current Julian date
       IDL> DAYCNV, JD, YR, MON, DAY, HOURS  ;Convert to hour,day month & year

 METHOD:
       A call is made to SYSTIME(/JULIAN,/UTC).

 REVISION HISTORY:
       Written Wayne Landsman                March, 1991
       Converted to IDL V5.0   W. Landsman   September 1997
       Assume since V5.4 Use /UTC keyword to SYSTIME()  W. Landsman April 2006

(See $IDLUTILS_DIR/goddard/pro/astro/get_juldate.pro)

GLACTC

 NAME:  
       GLACTC
 PURPOSE:
        Convert between celestial and Galactic (or Supergalactic) coordinates.
 EXPLANATION:
       Program to convert right ascension (ra) and declination (dec) to
       Galactic longitude (gl) and latitude (gb) (j=1) or vice versa (j=2).

 CALLING SEQUENCE: 
       GLACTC, ra, dec, year, gl, gb, j, [ /DEGREE, /FK4, /SuperGalactic ]

 INPUT PARAMETERS: 
       year     equinox of ra and dec, scalar       (input)
       j        direction of conversion     (input)
               1:  ra,dec --> gl,gb
               2:  gl,gb  --> ra,dec

 INPUTS OR OUTPUT PARAMETERS: ( depending on argument J )
       ra       Right ascension, hours (or degrees if /DEGREES is set), 
                         scalar or vector
       dec      Declination, degrees,scalar or vector
       gl       Galactic longitude, degrees, scalar or vector
       gb       Galactic latitude, degrees, scalar or vector

       All results forced double precision floating.

 OPTIONAL INPUT KEYWORD PARAMETERS:
       /DEGREE - If set, then the RA parameter (both input and output) is 
                given in degrees rather than hours. 
       /FK4 - If set, then the celestial (RA, Dec) coordinates are assumed
              to be input/output in the FK4 system.    By default,  coordinates
              are assumed to be in the FK5 system.    For B1950 coordinates,
              set the /FK4 keyword *and* set the year to 1950.
       /SuperGalactic - If set, the GLACTC returns SuperGalactic coordinates
              as defined by deVaucouleurs et al. (1976) to account for the 
              local supercluster. The North pole in SuperGalactic coordinates 
              has Galactic coordinates l = 47.47, b = 6.32, and the origin is 
              at Galactic coordinates l = 137.37, b= 0 
              
 EXAMPLES:
       Find the Galactic coordinates of Altair (RA (J2000): 19 50 47 
       Dec (J2000): 08 52 06)

       IDL> glactc, ten(19,50,47),ten(8,52,6),2000,gl,gb,1
       ==> gl = 47.74, gb = -8.91

 PROCEDURE CALLS:
       BPRECESS, JPRECESS, PRECESS
 HISTORY: 
       FORTRAN subroutine by T. A. Nagy, 21-MAR-78.
       Conversion to IDL, R. S. Hill, STX, 19-OCT-87.
       Modified to handle vector input, E. P. Smith, GSFC, 14-OCT-94
       Converted to IDL V5.0   W. Landsman   September 1997
       Added DEGREE keyword, C. Markwardt, Nov 1999
       Major rewrite, default now FK5 coordinates, added /FK4 keyword
       use external precession routines    W. Landsman   April 2002
       Add /Supergalactic keyword W. Landsman  September 2002
       Fix major bug when year not 2000 and /FK4 not set W. Landsman July 2003

(See $IDLUTILS_DIR/goddard/pro/astro/glactc.pro)

GLACTC_PM

 NAME:  
       GLACTC_PM
 PURPOSE:
        Convert between celestial and Galactic (or Supergalactic) proper
        motion (also converts coordinates).
 EXPLANATION:
       Program to convert proper motion in equatorial coordinates (ra,dec)
       to proper motion in Galactic coordinates (gl, gb) or Supergalacic 
       Coordinates  (sgl,sgb)  or back to equatorial coordinates (j=2).
       The proper motion unit is arbitrary, but be sure to set /MUSTAR if
       units are the projection of the proper motion on the RA, Dec axis.
       It does precession on the coordinates but does not
       take care of precession of the proper motions which is usually a
       very small effect.

 CALLING SEQUENCE: 
       GLACTC_PM, ra, dec, mu_ra,mu_dec,year, gl, gb, mu_gl, mu_gb, j, 
                  [ /DEGREE, /FK4, /SuperGalactic, /mustar ]

 INPUT PARAMETERS: 
       year     equinox of ra and dec, scalar       (input)
       j        direction of conversion     (input)
		1:  ra,dec,mu_ra,mu_dec --> gl,gb,mu_gl,mu_gb
		2:  gl,gb,mu_gl,mu_gb  --> ra,dec,mu_ra,mu_dec

 INPUTS OR OUTPUT PARAMETERS: ( depending on argument J )
       ra       Right ascension, hours (or degrees if /DEGREES is set), 
                         scalar or vector.  
       dec      Declination, degrees,scalar or vector
       mu_ra    right ascension proper motion any proper motion unit
					(angle/time)
       mu_dec    declination proper motion in any proper motion unit
					(angle/time)
       gl       Galactic longitude, degrees, scalar or vector
       gb       Galactic latitude, degrees, scalar or vector
       mu_gl    galactic longitude proper motion in any time unit
       mu_gb    galactic latitude proper motion in any time unit
       All results forced double precision floating.

 OPTIONAL INPUT KEYWORD PARAMETERS:
       /DEGREE - If set, then the RA parameter (both input and output) is 
                given in degrees rather than hours. 
       /FK4 - If set, then the celestial (RA, Dec) coordinates are assumed
              to be input/output in the FK4 system.    By default,  coordinates
              are assumed to be in the FK5 system.    For B1950 coordinates,
              set the /FK4 keyword *and* set the year to 1950.
       /SuperGalactic - If set, the GLACTC returns SuperGalactic coordinates
              as defined by deVaucouleurs et al. (1976) to account for the 
              local supercluster. The North pole in SuperGalactic coordinates 
              has Galactic coordinates l = 47.47, b = 6.32, and the origin is 
              at Galactic coordinates l = 137.37, b= 0 
	/mustar - if set then input and output of mu_ra and mu_dec are the 
                projections of mu in the ra or dec direction rather than
		the d(ra)/dt or d(mu)/dt.  So mu_ra becomes mu_ra*cos(dec)
               and mu_gl becomes mu_gl*cos(gb).
              
 EXAMPLES:
       Find the SuperGalactic proper motion of M33 given its
       equatorial proper motion mu* =(-29.3, 45.2) microas/yr.
       Where the (*) indicates ra component is actual mu_ra*cos(dec) 
		(Position: RA (J2000): 01 33 50.9, Dec (J2000): 30 39 36.8)

       IDL> glactc_pm, ten(1,33,50.9),ten(30,39,36.8),-29.3,45.2, 2000,$
				sgl,sgb,mu_sgl,mu_sgb,1,/Supergalactic,/mustar
       ==> SGL = 328.46732 deg, SGB = -0.089896901 deg, 
			mu_sgl = 33.732 muas/yr, mu_gb = 41.996 muas/yr.
         And for the roundtrip:
       IDL> glactc_pm, ra,dec,mu_ra,mu_dec,2000,$
       IDL>  sgl,sgb,mu_sgl,mu_sgb,2,/Supergalactic,/mustar
        ==> ra=1.5641376 hrs., dec= 30.660277 deg,
            mu_ra= -29.300000 muas/yr, mu_dec=i 45.200000 muas/yr

 PROCEDURE CALLS:
       BPRECESS, JPRECESS, PRECESS
 HISTORY: 
       Written                Ed Shaya, U of MD,  Oct 2009.
       Adapted from GLACTC  to make proper motion transformations, 
       Correct occasional sign error in galactic longitude E. Shaya  Nov 2011

(See $IDLUTILS_DIR/goddard/pro/astro/glactc_pm.pro)

GROUP

 NAME:
      GROUP
 PURPOSE:
      Assign stars with non-overlapping PSF profiles into distinct groups
 EXPLANATION:
      Part of the IDL-DAOPHOT sequence

 CALLING SEQUENCE:
      GROUP, X, Y, RCRIT, NGROUP

 INPUTS:
      X - vector, giving X coordinates of a set of stars.
      Y - vector, giving Y coordinates of a set of stars.
           If X and Y are input as integers, then they will be converted to 
           floating point
      RCRIT - scalar, giving minimum distance between stars of two
               distinct groups.  Stars less than this distance from
               each other are always in the same group.    Stetson suggests
               setting the critical distance equal to the PSF radius +
               the Fitting radius.

 OUTPUTS:
      NGROUP - integer vector, same number of elements as X and Y,
               giving a group number for each star position.  Group
               numbering begins with 0.

 METHOD:
      Each position is initially given a unique group number.  The distance
      of each star is computed against every other star.   Those distances
      less than RCRIT are assigned the minimum group number of the set.   A
      check is then made to see if any groups have merged together.

 PROCEDURES USED:
      REM_DUP()

 REVISION HISTORY:
      Written W. Landsman  STX                  April, 1988
      Major revision to properly merge groups together  W. Landsman   Sep 1991
      Work for more than 32767 points    W. Landsman  March 1997
      Converted to IDL V5.0   W. Landsman   September 1997
      Avoid overflow if X and Y are integers      W. Landsman  Feb. 1999

(See $IDLUTILS_DIR/goddard/pro/idlphot/group.pro)

GSSSADXY

 NAME:
      GSSSADXY
 PURPOSE:
       Converts RA and DEC (J2000) to (X,Y) for an STScI GuideStar image.   
 EXPLANATION:
       The sky coordinates may be printed and/or returned in variables.

 CALLING SEQUENCE:
       GSSSADXY, GSA, Ra,Dec, [ X, Y, /Print ] 

 INPUT:
       GSA - the GSSS Astrometry structure created by GSSSEXTAST
       RA  - the RA coordinate(s) in *degrees*, scalar or vector
       DEC - the DEC coordinate(s) in *degrees*, scalar or vector

 OPTIONAL KEYWORD INPUT:
       /PRINT - If this keyword is set and non-zero, then coordinates will be
               displayed at the terminal
 OUTPUT:
       X - the corresponding X pixel coordinate(s), double precision
       Y - the corresponding Y pixel coordinate(s), double precision

       X and Y will be in IDL convention (first pixel 0,0)
 EXAMPLE:
       Given a FITS header, hdr, from the STScI Guidestar Survey, determine
       the X,Y coordinates of 3C 273 (RA = 12 29 6.7  +02 03 08)

       IDL> GSSSEXTAST, hdr, gsa          ;Extract astrometry structure
       IDL> GSSSADXY, gsa, ten(12,29,6.7)*15,ten(2,3,8),/print

 NOTES:
       For most purpose users can simply use ADXY, which will call GSSSADXY
       if it is passed a GSSS header.

 PROCEDURES CALLED:
       ASTDISP - Print RA, Dec in standard format
 HISTORY:
       10-JUL-90 Version 1 written by Eric W. Deutsch
               Derived from procedures written by Brian McLean
       Vectorized code   W. Landsman        March, 1991
       14-AUG-91 Fixed error which caused returned X and Y to be .5 pixels too
               large.  Now X,Y follows same protocol as ADXY.
       June 1994 - Dropped PRFLAG parameter, added /PRINT  W. Landsman (HSTX)
       Converted to IDL V5.0   W. Landsman   September 1997
       29-JUN-99 Added support for AMD[X,Y]1[2-3] for DSS images by E. Deutsch
       Reduce memory requirements for large arrays D. Finkbeiner April 2004

(See $IDLUTILS_DIR/goddard/pro/astrom/gsssadxy.pro)

GSSSEXTAST

 NAME: 
      GSSSEXTAST

 PURPOSE:
      Extract IDL astrometry structure from a ST Guide Star Survey FITS header

 EXPLANATION:
      This procedure extracts the astrometry information from a ST Guide
      Star Survey FITS header and places it in an IDL structure for 
      subsequent use with GSSSxyad and GSSSadxy.

 CALLING SEQUENCE:
      GSSSExtast, hdr, astr, noparams
 INPUT:
      h - the GSSS FITS header
 OUTPUT:
      astr  - Structure containing the GSSS Astrometry information
               .CTYPE  =  ['RA---GSS','DEC--GSS'] 
               .CRVAL = plate center Ra, Dec (from PLTRAH, PLTRAM etc.)
               .XLL,.YLL = offsets lower lefthand corner
               .AMDX, .AMDY = 12 transformation coefficients
               .XSZ,.YSZ = X and Y pixel size in microns
               .PLTSCL = plate scale in arc sec/mm
               .PPO3, .PPO6 - orientation coefficients
 NOTES:
      Most users should use EXTAST rather than this procedure.   EXTAST will
      call GSSSEXTAST if supplied with GSSS FITS header.

 PROCEDURES CALLED:
      SXPAR() - Extract parameter values from a FITS header
 HISTORY:
       01-JUL-90 Version 1 written by Eric W. Deutsch
       Code derived from Software by Brian McLean
       20-AUG-91 Modified to Double Precision Variables.  E. Deutsch
       June 94 Change astrometry tags to better agree with EXTAST  W. Landsman
       Converted to IDL V5.0   W. Landsman   September 1997
       29-JUN-99 Added support for AMD[X,Y]1[2-3] for DSS images by E. Deutsch
       Eliminate use of obsolete !ERR  W. Landsman    February 2000

(See $IDLUTILS_DIR/goddard/pro/astrom/gsssextast.pro)

GSSSXYAD

 NAME:
       GSSSXYAD
 PURPOSE:
       Convert (X,Y) coordinates in a STScI Guide Star image to RA and Dec
 EXPLANATION:
       The sky coordinates may be printed and/or returned in variables.

 CALLING SEQUENCE:
       GSSSxyad, gsa, x, y, ra, dec, [ /PRINT ]
 INPUT:
       GSA  - The GSSS Astrometry structure extracted from a FITS header 
              by GSSSEXTAST
       X - The X pixel coordinate(s) of the image, scalar or vector
       Y - The Y pixel coordinate(s) of the image, scalar or vector

 OUTPUT:
       RA - The RA coordinate of the given pixel(s) in *degrees*
       DEC - The DEC coordinate of the given pixel(s) in *degrees*

       Both RA and Dec will be returned as double precision

 OPTIONAL KEYWORD INPUT:
       /PRINT - If this keyword is set and non-zero, then coordinates will be
               displayed at the terminal
 EXAMPLE:
       Given a FITS header,hdr, from a GSSS image, print the astronomical
       coordinates of (X,Y) = (200.23, 100.16) at the terminal

       IDL> GSSSExtast, hdr, gsa        ;Extract astrometry structure
       IDL> GSSSxyad, gsa, 200.23, 100.16, /print

 NOTES:
       For most purpose users can simply use XYAD, which will call GSSSXYAD
       if it is passed a GSSS header.

 PROCEDURES CALLED:
       ASTDISP - print RA, Dec in a standard format
 HISTORY:
       01-JUL-90 Version 1 written by Eric W. Deutsch
       Vectorized Code   W. Landsman        March, 1991
       14-AUG-91 Fixed error which caused returned RA and DEC to be off by
       -.5 pixels in both X,Y.  Now X,Y follows same protocol as ADXY.
       20-AUG-91 Modified to use AstDisp procedure.
       June 94 Added /PRINT keyword instead of PRFLAG W. Landsman June 94
       Converted to IDL V5.0   W. Landsman   September 1997
       29-JUN-99 Added support for AMD[X,Y]1[2-3] for DSS images by E. Deutsch

(See $IDLUTILS_DIR/goddard/pro/astrom/gsssxyad.pro)

GSSS_STDAST

 NAME:
      GSSS_STDAST

 PURPOSE:
      Insert the closest tangent projection astrometry into an GSSS Image
   
 DESCRIPTION:
       This procedure takes a header with GSSS (ST Guide Star Survey) 
       astrometry and writes a roughly equivalent tangent projection 
       astrometry into the header.     One might want to do this if (1)
       one needs to use software which does not recognize the GSSS astrometric
       parameters or (2) if the the image to be transformed, since the 
       highly nonlinear GSSS solution does not transform easily.  

 CALLING SEQUENCE:
       GSSS_STDAST, H, [Xpts, Ypts]

 INPUT - OUTPUT:
       H -  FITS header (string array) containing GSSS astrometry.  
       GSSS_STDAST will write the roughly equivalent tangent projection 
               astrometry solution into H.
 OPTIONAL INPUTS:
       xpts, ypts -- Vectors giving the X and Y positions of the three 
               reference points used to find approximate tangent projection.
               Default is Xpts = [0.2,0.8,0.5], Ypts = [0.2, 0.4, 0.8]
 METHOD:
       The procedures GSSSXYAD is used to exactly determine the RA and Dec
       at 3 reference points.    STARAST is then used to find the tangent
       projection astrometry that best matches these reference points.

 NOTES:
       Images from the STScI server (http://archive.stsci.edu/dss/) contain
       both a GSSS polynomial plate solution and an approximate WCS tangent
       projection.    The value  of the WCSNAME keyword in the FITS header 
       is 'DSS'.    If WCSNAME = "DSS' then the more accurate DSS astrometry
       is extracted by EXTAST    This procedure changes the value of WCSNAME  
       to 'DSS_TANGENT' to indicate that the tangent solution should be used.
    
       Some early GSSS images (before the 1994 CD-Rom) used keywords CRPIXx
       rather than CNPIXx.    The GSSS astrometry in these images could be
       corrupted by this procedure as the CRPIXx values will be altered.

       The tangent is only a approximation of the nonlinear GSSS astrometry,
       but is generally accurate to about 0.1 pixels on a 1024 x 1024 image.

 PROCEDURES USED:
       GSSSEXTAST, GSSSXYAD, STARAST, PUTAST, SXADDHIST, SXDELPAR

 HISTORY:
       13-AUG-91 Version 2 written from MAKEASTGSSS  Eric Deutsch (STScI)
       Delete CDELT* keywords from header   W. Landsman      May 1994
       Remove call to BUILDAST  W. Landsman                  Jan, 1995
       Added optional Xpts, Ypts parameters   E. Deutsch     Oct, 1995
       Add WCSNAME   W. Landsman                             Nov 2006

(See $IDLUTILS_DIR/goddard/pro/astrom/gsss_stdast.pro)

HADEC2ALTAZ

  NAME:
     HADEC2ALTAZ
  PURPOSE:
      Converts Hour Angle and Declination to Horizon (alt-az) coordinates.
  EXPLANATION:
      Can deal with NCP/SCP singularity.    Intended mainly to be used by
      program EQ2HOR

 CALLING SEQUENCE:
      HADEC2ALTAZ, ha, dec, lat ,alt ,az [ /WS ]

 INPUTS
     ha -  the local apparent hour angle, in DEGREES, scalar or vector
     dec -  the local apparent declination, in DEGREES, scalar or vector
     lat -  the local latitude, in DEGREES, scalar or vector

 OUTPUTS
     alt - the local apparent altitude, in DEGREES.
     az  - the local apparent azimuth, in DEGREES, all results in double
           precision
 OPTIONAL KEYWORD INPUT:
      /WS - Set this keyword for the output azimuth to be measured West from 
            South.    The default is to measure azimuth East from North.

 EXAMPLE:
     What were the apparent altitude and azimuth of the sun when it transited 
     the local meridian at Pine Bluff Observatory (Lat=+43.07833 degrees) on 
     April 21, 2002?   An object transits the local meridian at 0 hour angle.
     Assume this will happen at roughly 1 PM local time (18:00 UTC).

     IDL> jdcnv, 2002, 4, 21, 18., jd  ; get rough Julian date to determine 
                                       ;Sun ra, dec.
     IDL> sunpos, jd, ra, dec
     IDL> hadec2altaz, 0., dec, 43.078333, alt, az

       ===> Altitude alt = 58.90
            Azimuth  az = 180.0

 REVISION HISTORY:
      Written  Chris O'Dell Univ. of Wisconsin-Madison May 2002

(See $IDLUTILS_DIR/goddard/pro/astro/hadec2altaz.pro)

HASIMAGEMAGICK

 :Description:
   Searches for the ImageMagick "convert" command to see if ImageMagick is available 
   on the system.

 :Categories:
    Utilities
    
 :Params:
    none.
       
 :Keywords:
     version: out, optional, type=string
        Returns the version number of the ImageMagick convert command, if found.
          
 :Examples:
    Used to determine if the ImageMagick convert command is available::
       IDL> available = SearchForImageMagick(Version=version)
       IDL> IF available THEN Print, version
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 17 January 2011. DWF.

 :Copyright:
     Copyright (c) 2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/hasimagemagick.pro)

HASTROM

 NAME:
       HASTROM
 PURPOSE:
       Transformation of an image to align it with a reference image
 EXPLANATION:
       A  transformation is applied (using POLY_2D) to an image so that   
       its astrometry is identical with that in a reference header.  This
       procedure can be used to align two images.

 CALLING SEQUENCE:
       HASTROM, oldim, oldhd, newim, newhd, refhd, [MISSING =, INTERP = ]
                            or
       HASTROM, oldim, oldhd, refhd, [MISSING =, INTERP ={0,1,2}, NGRID =, 
                                      CUBIC =, DEGREE = ]

 INPUTS:
       OLDIM - Image array to be manipulated.  If only 3 parameters are
               supplied then OLDIM and OLDHD will be modified to contain 
               the output image array and header
       OLDHD - FITS header array for OLDIM, containing astrometry parameters
       REFHD - Reference header, containing astrometry parameters.  OLDIM
               will be rotated, shifted, and compressed or expanded until
               its astrometry matches that in REFHD.
 OUTPUTS:
       NEWIM - Image array after transformation has been performed.
               The dimensions of NEWIM will be identical to the NAXIS1 and 
               NAXIS2 keywords specified in REFHD.  Regions on the reference 
               image that do not exist in OLDIM can be assigned a value with
               the MISSING keyword.
       NEWHD - Updated FITS image header associated with NEWIM

 OPTIONAL INPUT KEYWORDS:
       MISSING - Set this keyword to a scalar value which will be assigned
               to pixels in the output image which are out of range of the
               supplied imput image.  If not supplied, then linear 
               extrapolation is used.   See the IDL manual on POLY_2D.
               ***NOTE: A bug was introduced into the POLY_2D function in IDL 
               V5.5 (fixed in V6.1) such that the MISSING keyword
               may not work properly with floating point data***
       INTERP - Scalar, one of 0, 1, or 2 determining type of interpolation
               0 nearest neighbor, 1 (default) bilinear interpolation, 
               2 cubic interpolation.
       CUBIC - a scalar value between -1 and 0 specifying cubic interpolation
               with the specified value as the cubic interpolation parameter.
              (see poly_2d for info).    Setting CUBIC to a value greater 
               than zero is equivalent to setting CUBIC = -1. 
       NGRID -  Integer scalar specifying the number of equally spaced grid 
               points on each axis to use to specify the transformation.   
               The value of NGRID must always be greater than DEGREE + 1.
               The default is DEGREE + 2 which equals 3 (9 total points) for
               DEGREE=1 (linear warping).
       DEGREE - Integer scalar specifying the degree of the transformation.
               See the routine POLYWARP for more info.   Default = 
               1 (linear transformation) unless polynomial ('SIP') distortion 
               parameters are present in either the input or reference FITS
               header.    In that case, the default degree is equal to the
               degree of the distortion polynomial.
 OPTIONAL OUTPUT KEYWORD:
       ERRMSG - If this keyword is supplied, then any error messages will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               
 NOTES:
       (1) The 3 parameter calling sequence is less demanding on virtual 
               memory.
       (2) The astrometry in OLDHD will be precessed to match the equinox
                given in REFHD.
       (3) If an ST Guidestar image is used for the reference header, then the
                output header will be converted to standard astrometry.  
 EXAMPLE:
       Suppose one has an image array, IM, and an associated FITS header H.
       One desires to warp the image array so that it is aligned with another
       image with a FITS header, HREF.    Both headers contain astrometry info.
       Set pixel values to 0 where there is no overlap between the input and
       reference image, and use linear interpolation (default)

       IDL> hastrom, IM, H, HREF, MISSING = 0

 PROCEDURES USED:
       ad2xy, check_FITS, extast, get_EQUINOX(), gsssextast, hprecess,
       putast, sxaddpar, sxaddhist, sxpar(), xy2ad, zparcheck

 REVISION HISTORY:
       Written  W. Landsman, STX Co.              Feb, 1989
       Updated to CHECK_FITS                      Dec, 1991
       New astrometry keywords                    Mar, 1994
       Recognize GSSS header   W. Landsman        June, 1994
       Added CUBIC keyword     W. Landsman        March, 1997
       Accept INTERP=0, Convert output GSS header to standard astrometry
                               W. Landsman        June 1998
       Remove calls to obsolete !ERR system variable   March 2000
       Added ERRMSG output keyword  W. Landsman    April 2000
       Need to re-extract astrometry after precession  W. Landsman Nov. 2000
       Check for distortion parameters in headers, add more FITS HISTORY
       information                        W. Landsman   February 2005
       Use different coefficient for nearest neighbor to avoid half-pixel
       shift with POLY_2D      W. Landsman   Aug 2006
       Return ERRMSG if no overlap between images  W. Landsman  Nov 2007
       Use V6.0 notation  W. Landsman  Jan 2012

(See $IDLUTILS_DIR/goddard/pro/astrom/hastrom.pro)

HBOXAVE

 NAME:
       HBOXAVE
 PURPOSE:
       Box average an image array and update the FITS header array
 EXPLANATION:
       The function BOXAVE() is used.  This procedure is recommended for 
       integer images when photometric precision is desired, because it 
       performs intermediate steps using REAL*4 arithmetic.   Otherwise, the 
       procedure HREBIN is much faster.

 CALLING SEQUENCE:
       HBOXAVE, Oldim, Oldhd, Newim, Hewhd, box
               or
       HBOXAVE, Oldim, Oldhd, box

 INPUTS:
       Oldim - the original image array
       Oldhd - the original image FITS header, string array

 OPTIONAL INPUTS:
       box - the box size to be used, integer scalar.  If omitted, then
               HBOXAVE will prompt for this parameter.

 OPTIONAL OUTPUTS:
       Newim - the image after boxaveraging
       Newhd - header for newim containing updated astrometry info
               If output parameters are not supplied, the program
               will modify the input parameters OLDIM and OLDHD
               to contain the new array and updated header.
 OPTIONAL KEYWORD OUTPUT:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               

 PROCEDURE:
       The parameters BSCALE, NAXIS1, NAXIS2, CRPIX1, and CRPIX2 and
       the CD (or CDELT) parameters are updated for the new FITS header.

 EXAMPLE:
       Compress the image in a FITS file 'image.fits' by a factor of 4 and 
       update the astrometry in the FITS header

       IDL> im = readfits('image.fits',hdr)    ;Read FITS file into IDL arrays
       IDL> hboxave, im, hdr, 4                ;Boxaverage by 4
       IDL> writefits,'image.fits',im,hdr      ;Write a new FITS file

 CALLED PROCEDURES:
       CHECK_FITS - Check that the FITS header is appropriate to the image
       BOXAVE() - Performs box averaging of an image
       SXPAR(), SXADDPAR - Read and write FITS keyword values

 MODIFICATION HISTORY:
       Written, Aug. 1986 W. Landsman, STI Corp.
       IDLV2 changes, sxaddpar format keyword added, J. Isensee, July,1990
       Fix 0.5 pixel offset in new CRPIX computation W. Landsman, Dec, 1991
       Update BSCALE even if no astrometry present   W. Landsman, May 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Added ERRMSG keyword, Use double formatting   W. Landsman   April 2000
       Recognize PC matrix astrometry format    W. Landsman   December 2001

(See $IDLUTILS_DIR/goddard/pro/astrom/hboxave.pro)

HCONGRID

 NAME:
       HCONGRID
 PURPOSE:
       CONGRID an image and update astrometry in a FITS header
 EXPLANATION:
       Expand or contract an image using CONGRID and update the 
       associated FITS header array.

 CALLING SEQUENCE:
       HCONGRID, oldhd                       ;Update FITS header only
       HCONGRID, oldim, oldhd, [ newim, newhd, newx, newy, /HALF_HALF
                                 CUBIC = , INTERP=, OUTSIZE=, ERRMSG=, ALT= ]

 INPUTS:
       OLDIM - the original image array
       OLDHD - the original image FITS header, string array

 OPTIONAL INPUTS:
       NEWX - size of the new image in the X direction
       NEWY - size of the new image in the Y direction
               The OUTSIZE keyword can be used instead of the 
               NEWX, NEWY parameters

 OPTIONAL OUTPUTS:
       NEWIM - the image after expansion or contraction with CONGRID
       NEWHD - header for newim containing updated astrometry info
               If output parameters are not supplied, the program
               will modify the input parameters OLDIM and OLDHD
               to contain the new array and updated header.

 OPTIONAL KEYWORD INPUTS:
      ALT - Single character 'A' through 'Z' or ' ' specifying which astrometry
          system to modify in the FITS header.    The default is to use the
          primary astrometry of ALT = ' '.    See Greisen and Calabretta (2002)
          for information about alternate astrometry keywords.

       CUBIC - If set and non-zero, then cubic interpolation is used.   Valid
               ranges are  -1 <= Cubic < 0.   Setting /CUBIC is equivalent to
               CUBIC = -1 and also equivalent to INTERP = 2.   See INTERPOLATE
               for more info.    Setting CUBIC = -0.5 is recommended.
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               
       /HALF_HALF - Due to edge effects, the default behaviour of CONGRID is 
           to introduce a slight shift in the image center.  Craig Markwardt
           (http://cow.physics.wisc.edu/~craigm/idl/misc.html) has written
           a modified version of CONGRID called CMCONGRID that when used with
           the /HALF_HALF keyword eliminates any shift.   The use of the 
           /HALF keyword emulates CMCONGRID and eliminates any shift in the
           image centroid. 
       INTERP   - 0 for nearest neighbor, 1 for bilinear interpolation
               (default), 2 for cubic (=-1) interpolation.   
       OUTSIZE - Two element integer vector which can be used instead of the
               NEWX and NEWY parameters to specify the output image dimensions
 OPTIONAL KEYWORD OUTPUT:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               
 PROCEDURE:
       Expansion or contraction is done using the CONGRID function, unless
       HALF_HALF is set. 

       The parameters BSCALE, NAXIS1, NAXIS2, CRPIX1, and CRPIX2 and
       the CD (or CDELT) parameters are updated for the new header.

 NOTES:
       A FITS header can be supplied as the first parameter without having
       to supply an image array.   The astrometry in the FITS header will be
       updated to be appropriate to the specified image size.

       If the FITS header contains astrometry from a ST Guide Star image,
       then the astrometry will be converted to an approximately equivalent
       tangent projection before applying CONGRID.
 EXAMPLE:
       Congrid an 512 x 512 image array IM and FITS header H to size 300 x 300
       using cubic interpolation.   Use the HALF_HALF keyword to avoid 
       a shift of the image centroid

       IDL> hcongrid, IM ,H, OUT = [300, 300], CUBIC = -0.5, /HALF

       The variables IM and H will be modified to the new image size.

 PROCEDURES CALLED:
       CHECK_FITS, CONGRID(), EXTAST, GSSS_STDAST, SXADDHIST, 
       SXADDPAR, SXPAR(), ZPARCHECK
 MODIFICATION HISTORY:
       Written, Aug. 1986 W. Landsman, STI Corp.
       Added interp keywords, J. Isensee, July, 1990
       Add cubic interpolation W. Landsman HSTX   January 1994
       Recognize a GSSS FITS header   W. Landsman   June 1994
       Fix case where header but not image supplied  W. Landsman  May 1995
       Remove call to SINCE_VERSION()   W. Landsman   March 1996
       Assume since IDL V3.5, add CUBIC keyword      W. Landsman   March 1997
       Update BSCALE even if no astrometry present   W. Landsman   May 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Added HALF_HALF keyword  W. Landsman  February 2000
       Added ERRMSG keyword, use double precision formatting W.L.  April 2000
       Recognize PC00n00m astrometry format  W. Landsman   December 2001
       Now works when both /INTERP and /HALF are set W. Landsman January 2002
       Fix output astrometry for non-equal plate scales for PC matrix or
       CROTA2 keyword, added ALT keyword.   W. Landsman May 2005
       Update distortion parameters if present  W. Landsman January 2008
       Don't update BSCALE/BZERO for unsigned integer W.Landsman Mar 2008

(See $IDLUTILS_DIR/goddard/pro/astrom/hcongrid.pro)

HEADFITS

 NAME:
       HEADFITS
 PURPOSE:
       Read a FITS (primary or extension) header into a string array.
 EXPLANATION:
       HEADFITS() supports several types of compressed files including 
       gzip (.gz), Unix compressed (.Z), Bzip2 (.bz2) or FPACK (.fz 
       http://heasarc.gsfc.nasa.gov/fitsio/fpack/ )

 CALLING SEQUENCE:
       Result = HEADFITS(Filename/Fileunit ,[ ERRMSG =, EXTEN= , COMPRESS=, 
                                            /SILENT ])

 INPUTS:
       Filename = String containing the name of the FITS file to be read.
                If set to an empty string, then user will be prompted for name.
                File names ending in '.gz' are assumed to be gzip'ed compressed
                and under Unix file names ending in '.Z' are assumed to be
                Unix compressed, and file names ending in .bz2 are assumed to
                be bzip2 compressed.    If this default behaviour is not 
                sufficient then use the COMPRESS keyword.
                            or
       Fileunit - A scalar integer specifying the unit of an already opened
                  FITS file.  The unit will remain open after exiting 
                  HEADFITS().  There are two possible reasons for choosing 
                  to specify a unit number rather than a file name:
          (1) For a FITS file with many extensions, one can move to the 
              desired extensions with FXPOSIT() and then use HEADFITS().  This
              is more efficient that repeatedly starting at the beginning of 
              the file.
          (2) For reading a FITS file across a Web http: address after opening
              the unit with the SOCKET procedure.
 OPTIONAL INPUT KEYWORDS:
      EXTEN  = Either an integer scalar, specifying which FITS extension to 
               read, or a scalar string specifying the extension name (stored
               in the EXTNAME keyword).   For example, to read the header of 
               the first extension set EXTEN = 1.   Default is to read the 
               primary FITS header  (EXTEN = 0).    The EXTEN keyword cannot 
               be used when a unit number is supplied instead of a file name.
     COMPRESS - If this keyword is set and non-zero, then treat the file
              as compressed.  If 1 assume a gzipped file.   Use IDL's
              internal decompression facilities for gzip files, while for 
              Unix or bzip2 compression spawn off a process to decompress and 
              use its output as the FITS stream.  If the keyword is not 1, 
              then use its value as a string giving the command needed for 
              decompression.   See FXPOSIT for more info.
     /SILENT - If set, then suppress any warning messages about invalid 
              characters in the FITS file.
 OPTIONAL KEYWORD OUTPUT:
       ERRMSG	= If this keyword is present, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.  

 OUTPUTS:
       Result of function = FITS header, string array

 EXAMPLE:
       Print the main FITS header of a file 'test.fits' into a string 
       variable, h

       IDL>  print, headfits( 'test.fits')

       Print the second extension header of a gzip compressed FITS file
       'test.fits.gz'.  Use HPRINT for pretty format

       IDL> hprint, headfits( 'test.fits.gz', ext=2)

       Read the extension named CALSPEC 

       IDL> hprint,headfits('test.fits.gz',ext='CALSPEC')

 PROCEDURES CALLED
       FXPOSIT(), MRD_HREAD
       The version of fxposit.pro must be post- May 2009.
 MODIFICATION HISTORY:
       adapted by Frank Varosi from READFITS by Jim Wofford, January, 24 1989
       Keyword EXTEN added, K.Venkatakrishna, May 1992
       Make sure first 8 characters are 'SIMPLE'  W. Landsman October 1993
       Check PCOUNT and GCOUNT   W. Landsman    December 1994
       Major rewrite, work for Unix gzip files,   W. Landsman  April 1996
       Added COMPRESS keyword  W. Landsman   April 2000
       Added ERRMSG keyword    W. Landsman   July 2000
       Added /SILENT keyword   W. Landsman    December 2000
       Option to read a unit number rather than file name W.L    October 2001
       Test output status of MRD_HREAD call October 2003 W. Landsman
       Allow extension to be specified by name Dec 2006 W. Landsman
       No need to uncompress FPACK compressed files  May 2009 W. Landsman
       Use V6.0 notation   W.L.   Feb. 2011

(See $IDLUTILS_DIR/goddard/pro/fits/headfits.pro)

HELIO

 NAME: 
      HELIO
 PURPOSE: 
      Compute (low-precision) heliocentric coordinates for the planets.
 EXPLANATION:
      The mean orbital elements for epoch J2000 are used.   These are derived
      from a 250 yr least squares fit of the DE 200 planetary ephemeris to a 
      Keplerian orbit where each element is allowed to vary linearly with 
      time.  For dates between 1800 and 2050, this solution fits the 
      terrestrial planet orbits to ~25" or better, but achieves only ~600" 
      for Saturn.   

      Use PLANET_COORDS (which calls HELIO) to get celestial (RA, Dec)
      coordinates of the planets
 CALLING SEQUENCE: 
       HELIO, JD, LIST, HRAD, HLONG, HLAT, [/RADIAN]
 INPUTS:
       JD = Julian date, double precision scalar or vector
       LIST = List of planets array.  May be a single number.
               1 = merc, 2 = venus, ... 9 = pluto.

 OUTPUTS:
       HRAD = array of Heliocentric radii (A.U).
       HLONG = array of Heliocentric (ecliptic) longitudes (degrees).
       HLAT = array of Heliocentric latitudes (degrees).
             These output parameters will be dimensioned Nplanet by Ndate,
             where Nplanet is the number of elements of list, and Ndate is 
             the number of elements of JD.

 OPTIONAL INPUT KEYWORD:
       /RADIAN - If set, then the output longitude and latitude are given in 
                 radians.         
 EXAMPLE:
       (1) Find the current heliocentric positions of all the planets

        IDL> GET_JULDATE, jd      ;Get current Julian date
        IDL> HELIO,jd,indgen(9)+1,hrad,hlong,hlat  ;Get radius, long, and lat

       (2) Find heliocentric position of Mars on August 23, 2000 
         IDL> JDCNV, 2000,08,23,0,jd
         IDL> HELIO,JD,2,HRAD,HLONG,HLAT
                  ===> hrad = 1.6407 AU hlong = 124.3197 hlat = 1.7853
         For comparison, the JPL ephemeris gives
                       hrad = 1.6407 AU hlong = 124.2985 hlat = 1.7845
       (3) Find the heliocentric positions of Mars and Venus for every day in
           November 2000
        IDL> JDCNV, 2000, 11, 1, 0, jd    ;Julian date of November 1, 2000
        IDL> helio, jd+indgen(30), [4,2], hrad,hlong,hlat   ;Mars=4, Venus=2 
                   hrad, hlong, and hlat will be dimensioned [2,30]
                   first column contains Mars data, second column Venus
 COMMON BLOCKS: 
       None 
 ROUTINES USED: 
       CIRRANGE - force angle between 0 and 2*!PI
 NOTES:
       (1) The calling sequence for this procedure was changed in August 2000
       (2) This program is based on the two-body model and thus neglects 
           interactions between the planets.   This is why the worst results
           are for Saturn.  Use the procedure JPLEPHINTERp for more accurate
           positions using the JPL ephemeris.   Also see 
           http://ssd.jpl.nasa.gov/cgi-bin/eph for a more accurate ephemeris 
           generator online.     
       (3) The coordinates are given for equinox 2000 and *not* the equinox
           of the supplied date(s)
 MODIFICATION HISTORY: 
       R. Sterner.  20 Aug, 1986.
       Code cleaned up a bit      W. Landsman             December 1992
       Major rewrite, use modern orbital elements, vectorize, more accurate
         solution to Kepler's equation          W. Landsman August 2000
       Wasn't working for planet vectors        W. Landsman August 2000
       Work for more than 32767 positions       S. Leach Jan 2009

(See $IDLUTILS_DIR/goddard/pro/astro/helio.pro)

HELIO_JD

 NAME:
      HELIO_JD
 PURPOSE:
      Convert geocentric (reduced) Julian date to heliocentric Julian date
 EXPLANATION:
      This procedure correct for the extra light travel time between the Earth 
      and the Sun.

       An online calculator for this quantity is available at 
       http://www.physics.sfasu.edu/astro/javascript/hjd.html

       Users requiring more precise calculations and documentation should 
       look at the IDL code available at 
       http://astroutils.astronomy.ohio-state.edu/time/
 CALLING SEQUENCE:
       jdhelio = HELIO_JD( date, ra, dec, /B1950, /TIME_DIFF)

 INPUTS
       date - reduced Julian date (= JD - 2400000), scalar or vector, MUST
               be double precision
       ra,dec - scalars giving right ascension and declination in DEGREES
               Equinox is J2000 unless the /B1950 keyword is set

 OUTPUTS:
       jdhelio - heliocentric reduced Julian date.  If /TIME_DIFF is set, then
                 HELIO_JD() instead returns the time difference in seconds
                 between the geocentric and heliocentric Julian date.
                 
 OPTIONAL INPUT KEYWORDS 
       /B1950 - if set, then input coordinates are assumed to be in equinox 
                B1950 coordinates.
       /TIME_DIFF - if set, then HELIO_JD() returns the time difference
                (heliocentric JD - geocentric JD ) in seconds 

 EXAMPLE:
       What is the heliocentric Julian date of an observation of V402 Cygni
       (J2000: RA = 20 9 7.8, Dec = 37 09 07) taken June 15, 1973 at 11:40 UT?

       IDL> juldate, [1973,6,15,11,40], jd      ;Get geocentric Julian date
       IDL> hjd = helio_jd( jd, ten(20,9,7.8)*15., ten(37,9,7) )  
                                                            
       ==> hjd = 41848.9881

 Wayne Warren (Raytheon ITSS) has compared the results of HELIO_JD with the
 FORTRAN subroutines in the STARLINK SLALIB library (see 
 http://star-www.rl.ac.uk/).    
                                                  Time Diff (sec)
      Date               RA(2000)   Dec(2000)  STARLINK      IDL

 1999-10-29T00:00:00.0  21 08 25.  -67 22 00.  -59.0        -59.0
 1999-10-29T00:00:00.0  02 56 33.4 +00 26 55.  474.1        474.1
 1940-12-11T06:55:00.0  07 34 41.9 -00 30 42.  366.3        370.2
 1992-02-29T03:15:56.2  12 56 27.4 +42 10 17.  350.8        350.9
 2000-03-01T10:26:31.8  14 28 36.7 -20 42 11.  243.7        243.7
 2100-02-26T09:18:24.2  08 26 51.7 +85 47 28.  104.0        108.8
 PROCEDURES CALLED:
       bprecess, xyz, zparcheck

 REVISION HISTORY:
       Algorithm from the book Astronomical Photometry by Henden, p. 114
       Written,   W. Landsman       STX     June, 1989 
       Make J2000 default equinox, add B1950, /TIME_DIFF keywords, compute
       variation of the obliquity      W. Landsman   November 1999

(See $IDLUTILS_DIR/goddard/pro/astro/helio_jd.pro)

HELIO_RV

 NAME:
    HELIO_RV

 PURPOSE:
     Return the heliocentric radial velocity of a spectroscopic binary

 EXPLANATION:
    This function will return the heliocentric radial velocity of a 
    spectroscopic binary star at a given heliocentric date 
    given its orbit.

 CALLING SEQUENCE:

  Result = HELIO_RV ( JD ,T ,Period ,Gamma , K, [,e ,Omega ] )

 INPUT:

 JD            - Time of observation
 T             - Time of periastron passage (max. +ve velocity
                 for circular orbits), same time system as JD
 Period        - the period in same units as JD
 Gamma         - systemic velocity
 K             - velocity semi-amplitude in the same units as Gamma.
 e             - eccentricity of the orbit, default is 0.
 Omega         - longitude of periastron in degrees. Must be specified for
                 eccentric orbits.

 OUTPUT:

  The predicted heliocentric radial velocity in the same units as Gamma
  for the date(s) specified by Reduced_HJD.

 RESTRICTIONS:

  The user should ensure consistency with all time systems being
  used (i.e. JD and T should be in the same units and time system).
  Generally, users should reduce large time values by subtracting 
  a large constant offset, which may improve numerical accuracy.
  
  If using the the routines JULDATE and HELIO_JD, the reduced HJD
  time system must be used throughtout.

 EXAMPLES:

 Example 1

  What was the heliocentric radial velocity of the primary component of HU Tau
 at 1730 UT 25 Oct 1994?
 
 IDL> juldate ,[94,10,25,17,30],JD                 ;Get Geocentric julian date
 IDL> hjd = helio_jd(jd,ten(04,38,16)*15.,ten(20,41,05)) ; Convert to HJD
 IDL> print, helio_rv(hjd,46487.5303D,2.0563056D,-6.0,59.3)
      -62.965569

 NB. 1. The routines JULDATE and HELIO_JD return a reduced HJD (HJD - 2400000)
        and so T and P must be specified in the same fashion.
     2. The user should be careful to use double precision format to specify
        T and P to sufficient precision where necessary. 
 
 Example 2

  Plot two cycles of an eccentric orbit, e=0.6, omega=45 for both
  components of a binary star

 IDL> phi=findgen(100)/50.0             ; Generates 100 phase points
 IDL> plot, phi,helio_rv(phi,0,1,0,100,0.6,45),yrange=[-100,150]
 IDL> oplot, phi,helio_rv(phi,0,1,0,50,0.6,45+180)
 
 This illustrates both the use of arrays to perform multiple calculations
 and generating radial velocities for a given phase by setting T=0 and P=1.
 Note also that omega has been changed by 180 degrees for the orbit of the
 second component  (the same 'trick' can be used for circular orbits).

 
 MODIFICATION HISTORY:

  Written by:  Pierre Maxted CUOBS, October, 1994

  Circular orbits handled by setting e=0 and omega=0 to allow
  binary orbits to be handled using omega and omega+180.
                                                      Pierre Maxted,Feb 95
  BUG - omega was altered by the routine - corrected Feb 95,Pierre Maxted
  Iteration for E changed to that  given by Reidel , Feb 95,Pierre Maxted
  /SINGLE keyword removed.                           May 96,Pierre Maxted
;       
  Removed limitation of time system on HJD, C. Markwardt, 2011-04-15

  Change convergence test from relative to absolute precision on E
                                                     Pierre Maxted, Apr 12

(See $IDLUTILS_DIR/goddard/pro/astro/helio_rv.pro)

HERMITE

 NAME:
       HERMITE
 PURPOSE:
       To compute Hermite spline interpolation of a tabulated function.
 EXPLANATION:
       Hermite interpolation computes the cubic polynomial that agrees with 
       the tabulated function and its derivative at the two nearest 
       tabulated points.   It may be preferable to Lagrangian interpolation 
       (QUADTERP) when either (1) the first derivatives are known, or (2)
       one desires continuity of the first derivative of the interpolated
       values.    HERMITE() will numerically compute the necessary
       derivatives, if they are not supplied.
       
 CALLING SEQUENCE:
       F = HERMITE( XX, FF, X, [ FDERIV = ])

 INPUT PARAMETERS:
       XX - Vector giving tabulated X values of function to be interpolated
               Must be either monotonic increasing or decreasing   
       FF - Tabuluated values of function, same number of elements as X
       X -  Scalar or vector giving the X values at which to interpolate

 OPTIONAL INPUT KEYWORD:
       FDERIV - function derivative values computed at XX.    If not supplied,
               then HERMITE() will compute the derivatives numerically.
               The FDERIV keyword is useful either when (1) the derivative
               values are (somehow) known to better accuracy than can be 
               computed numerically, or (2) when HERMITE() is called repeatedly
               with the same tabulated function, so that the derivatives
               need be computed only once.

 OUTPUT PARAMETER:
       F - Interpolated values of function, same number of points as X

 EXAMPLE:
       Interpolate the function 1/x at x = 0.45 using tabulated values
       with a spacing of 0.1

       IDL> x = findgen(20)*0.1 + 0.1
       IDL> y = 1/x
       IDL> print,hermite(x,y,0.45)         
               This gives 2.2188 compared to the true value 1/0.45 = 2.2222

       IDL> yprime = -1/x^2      ;But in this case we know the first derivatives
       IDL> print,hermite(x,y,0.45,fderiv = yprime)
             == 2.2219            ;and so can get a more accurate interpolation
 NOTES:
       The algorithm here is based on the FORTRAN code discussed by 
       Hill, G. 1982, Publ Dom. Astrophys. Obs., 16, 67.   The original 
       FORTRAN source is U.S. Airforce. Surveys in Geophysics No 272. 

       HERMITE() will return an error if one tries to interpolate any values 
       outside of the range of the input table XX
 PROCEDURES CALLED:
       None
 REVISION HISTORY:
       Written,    B. Dorman (GSFC) Oct 1993, revised April 1996
       Added FDERIV keyword,  W. Landsman (HSTX)  April 1996
       Test for out of range values  W. Landsman (HSTX) May 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Use VALUE_LOCATE instead of TABINV   W. Landsman   February 2001

(See $IDLUTILS_DIR/goddard/pro/math/hermite.pro)

HEULER

 NAME:
      HEULER 

 PURPOSE:
       Change the coordinate system of a FITS header or astrometry structure
 EXPLANATION:
       Converts a FITS header or a astrometry structure containing WCS (world 
       coordinate system) information between celestial, ecliptic, and 
       Galactic coordinates

 CALLING SEQUENCE:
       HEULER, hdr, [/GALACTIC, /CELESTIAL, /ECLIPTIC, ALT_IN = , ALT_OUT=]  
                      or
       HEULER, astr, /GALACTIC, /CELESTIAL, /ECLIPTIC

 INPUT/OUTPUT PARAMETERS:
       hdr - FITS header (string array) containing WCS information
                            or
       Astr - Astrometry structure as extracted from a FITS header
             by extast.pro (See EXTAST for more info).

       Header or astrometry structure will be modified by the program to 
       contain astrometry in the new coordinates system.
 REQUIRED INPUT KEYWORDS:
       One of the following exclusive keywords is *required*
       /GALACTIC - Convert the header to Galactic coordinates
       /CELESTIAL - Convert the header to celestial (RA & Dec) coordinates
       /ECLIPTIC - Convert the header to ecliptic coordinates

 OPTIONAL INPUT KEYWORDS:
      The following two keywords apply if the FITS header contains multiple
      WCS keywords. See Section 3.3 of Greisen & Calabretta (2002, A&A, 395, 
      1061) for information about alternate astrometry keywords.

      ALT_IN -  single character 'A' through 'Z' or ' ' specifying an 
          alternate astrometry system present in the input FITS header.  The 
          default isto use the primary astrometry or ALT = ' '.   If /ALT_IN 
          is set, then this is equivalent to ALT_IN = 'A'.
      ALT_OUT - single character specifying the alternate WCS keywords 
          to write the *output* astrometry.    If not specified, then ALT_OUT
          is set equal to ALT_IN.
 RESTRICTIONS:
       Currently assumes that celestial and ecliptic coordinates are in
       J2000.   Use HPRECESS if this is not the case.

       ST Guide Star (DSS) image headers are first converted to a standard
       tangent projection, prior to the coordinate conversion
 METHOD:
       The algorithm used is described in Section 2.7 of Calabretta & Greisen
       (2002, A&A, 395, 1077).    The CRVAL coordinates are transformed
       directly using EULER.    The new LONPOLE and LATPOLE values are then
       determined by transforming the pole of the new system to the old, and
       converted to native coordinates using WCS_ROTATE. 
 EXAMPLE:
       A FITS header, hdr, has a standard tangent projection WCS information.
       Add an alternate 'G' Galactic projection.    Note that the original
       WCS information will be left unchanged 

       IDL> heuler, hdr, /Galactic, alt='G'
 PROCEDURES USED:
       EULER, EXTAST, GSSS_STDAST, PUTAST, SXADDHIST, WCS_ROTATE
 REVISION HISTORY:
       Written    W. Landsman                  June 2003
       Use PV2 tag in astrometry structure rather than PROJP1 W. L. May 2004
       Use double precision to compute new North pole  W.L. Aug 2005

(See $IDLUTILS_DIR/goddard/pro/astrom/heuler.pro)

HEXTRACT

 NAME:
       HEXTRACT
 PURPOSE:
       Extract a subimage from an array and update astrometry in FITS header
 EXPLANATION:
       Extract a subimage from an array and create a new FITS header with
       updated astrometry for the subarray
 CALLING SEQUENCE:
       HEXTRACT, Oldim, Oldhd, [ Newim, Newhd, x0, x1, y0, y1, /SILENT ]
               or
       HEXTRACT, Oldim, Oldhd, [x0, x1, y0, y1, /SILENT, ERRMSG =  ]    

 INPUTS:
       Oldim - the original image array
       Oldhd - the original image header

 OPTIONAL INPUTS:
       x0, x1, y0, y1 - respectively, first and last X pixel, and first and
       last Y pixel to be extracted from the original image, integer scalars.
       HEXTRACT will convert these values to long integers. 
       If omitted,  HEXTRACT will prompt for these parameters

 OPTIONAL OUTPUTS:
       Newim - the new subarray extracted from the original image 
       Newhd - header for newim containing updated astrometry info
               If output parameters are not supplied or set equal to
               -1, then the HEXTRACT will modify the input parameters 
               OLDIM and OLDHD to contain the subarray and updated header.

 OPTIONAL INPUT KEYWORD:
      ALT - Single character 'A' through 'Z' or ' ' specifying which astrometry
          system to modify in the FITS header.    The default is to use the
          primary astrometry or ALT = ' '.    See Greisen and Calabretta (2002)
          for information about alternate astrometry keywords.
      /SILENT - If set and non-zero, then a message describing the extraction
               is not printed at the terminal.   This message can also be 
               suppressed by setting !QUIET.
 OPTIONAL KEYWORD OUTPUT:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               

 PROCEDURE:
       The FITS header parameters NAXIS1, NAXIS2, CRPIX1, and CRPIX2 are
       updated for the extracted image.

 EXAMPLE:  
       Read an image from a FITS file 'IMAGE', extract a 512 x 512 subimage 
       with the same origin, and write to a new FITS file 'IMAGENEW'

       IDL> im = READFITS( 'IMAGE', hdr )      ;Read FITS files into IDL arrays
       IDL> hextract, im, h, 0, 511, 0, 511    ;Extract 512 x 512 subimage
       IDL> writefits, 'IMAGENEW', im ,h       ;Write subimage to a FITS file

 PROCEDURES CALLED
       CHECK_FITS, STRN(), SXPAR(), SXADDPAR, SXADDHIST
 MODIFICATION HISTORY:
       Written, Aug. 1986 W. Landsman, STX Corp.
       Use astrometry structure,   W. Landsman      Jan, 1994
       Minor fix if bad Y range supplied   W. Landsman    Feb, 1996
       Added /SILENT keyword              W. Landsman     March, 1997
       Added ERRMSG keyword    W. Landsman   May 2000
       Work for dimensions larger than 32767   W.L., M.Symeonidis Mar 2007
       Added ALT keyword  W.L. April 2007

(See $IDLUTILS_DIR/goddard/pro/astrom/hextract.pro)

HGREP

 NAME:
     HGREP

 PURPOSE:
       Find a substring in a FITS header (or any other string array)

 CALLING SEQUENCE:
       HGREP, header, substring, [/KEEPCASE, /LINENUM ]

 INPUTS: 
       header -  FITS header or other string array
       substring - scalar string to find in header; if a numeric value is 
                 supplied, it will be converted to type string

 OPTIONAL INPUT KEYWORDS:
       /KEEPCASE: if set, then look for an exact match of the input substring 
                 Default is to ignore case .
       /LINENUM: if set, prints line number of header in which
                substring appears 

 OUTPUTS:
       None, results are printed to screen

 EXAMPLE: 
       Find every place in a FITS header that the word 'aperture'
       appears in lower case letters and print the element number 
       of the header array:
       
       IDL> hgrep, header, 'aperture', /keepcase, /linenum

 HISTORY: 
       Written, Wayne Landsman (Raytheon ITSS)      August 1998
       Adapted from STIS version by Phil Plait/ ACC November 14, 1997
       Remove trailing spaces if a non-string is supplied W. Landsman Jun 2002

(See $IDLUTILS_DIR/goddard/pro/misc/hgrep.pro)

HISTOGAUSS

NAME:
       HISTOGAUSS

 PURPOSE:
       Histograms data and overlays it with a Gaussian. Draws the mean, sigma,
       and number of points on the plot.

 CALLING SEQUENCE:
       HISTOGAUSS, Sample, A, [XX, YY, GX, GY, /NOPLOT, /NOFIT, FONT=, 
                               CHARSIZE = ]

 INPUT:
       SAMPLE = Vector to be histogrammed

 OUTPUT ARGUMENTS:
       A = coefficients of the Gaussian fit: Height, mean, sigma
               A[0]= the height of the Gaussian
               A[1]= the mean
               A[2]= the standard deviation
               A[3]= the half-width of the 95% conf. interval of the standard
                     mean
               A[4]= 1/(N-1)*total( (y-mean)/sigma)^2 ) = a measure of 
                       normality

       Below: superceded. The formula is not entirely reliable.
       A[4]= measure of the normality of the distribution. =1.0, perfectly
       normal. If no more than a few hundred points are input, there are
       formulae for the 90 and 95% confidence intervals of this quantity:
       M=ALOG10(N-1) ; N = number of points
       T90=ABS(.6376-1.1535*M+.1266*M^2)  ; = 90% confidence interval
       IF N LT 50 THEN T95=ABS(-1.9065-2.5465*M+.5652*M^2) $
                  ELSE T95=ABS( 0.7824-1.1021*M+.1021*M^2)   ;95% conf.
       (From Martinez, J. and Iglewicz, I., 1981, Biometrika, 68, 331-333.)

       XX = the X coordinates of the histogram bins (CENTER)
       YY = the Y coordinates of the histogram bins
       GX = the X coordinates of the Gaussian fit
       GY = the Y coordinates of the Gaussian fit

 OPTIONAL INPUT KEYWORDS:
       /NOPLOT - If set, nothing is drawn
       /FITIT   If set, a Gaussian is actually fitted to the distribution.
               By default, a Gaussian with the same mean and sigma is drawn; 
               the height is the only free parameter.
       CHARSIZE Size of the characters in the annotation. Default = 0.82.
       FONT - scalar font graphics keyword (-1,0 or 1) for text
       /WINDOW - set to plot to a resizeable graphics window
       _EXTRA - Any value keywords to the cgPLOT command (e.g. XTITLE) may also
               be passed to HISTOGAUSS
 SUBROUTINE CALLS:
       BIWEIGHT_MEAN, which determines the mean and std. dev.
       AUTOHIST, which draws the histogram
       GAUSSFIT() (IDL Library) which does just that

 REVISION HISTORY:
       Written, H. Freudenreich, STX, 12/89
       More quantities returned in A, 2/94, HF
       Added NOPLOT keyword and print if Gaussian, 3/94
       Stopped printing confidence limits on normality 3/31/94 HF
       Added CHARSIZE keyword, changed annotation format, 8/94 HF
       Simplified calculation of Gaussian height, 5/95 HF
       Convert to V5.0, use T_CVF instead of STUDENT_T, GAUSSFIT instead of
           FITAGAUSS  W. Landsman April 2002 
       Correct call to T_CVF for calculation of A[3], 95% confidence interval
                P. Broos/W. Landsman   July 2003
       Allow FONT keyword to be passed.  T. Robishaw Apr. 2006
       Use Coyote Graphics for plotting W.L. Mar 2011
       Better formatting of text output W.L. May 2012

(See $IDLUTILS_DIR/goddard/pro/robust/histogauss.pro)

HOR2EQ

 NAME:
   HOR2EQ

 PURPOSE:
    Converts local horizon coords (alt-az) of something to equatorial (ra-dec).

 EXPLANATION:
     This is a nice code to calculate equatorial (ra,dec) coordinates from
     horizon (alt,az) coords.    It is typically accurate to about 1 arcsecond
     or better (I have checked the output against the publicly available XEPHEM
     software). It performs precession, nutation, aberration, and refraction
     corrections.  The perhaps best thing about it is that it can take arrays
     as inputs, in all variables and keywords EXCEPT Lat, lon, and Altitude
    (the code assumes these aren't changing), and uses vector arithmetic in
     every calculation except when calculating the precession matrices.

 CALLING SEQUENCE:

    HOR2EQ, alt, az, jd, ra, dec, [ha, LAT= , LON= , /WS, OBSNAME= , $
                       /B1950 , PRECESS_= 0, NUTATE_= 0, REFRACT_= 0, $
                       ABERRATION_= 0, ALTITUDE= , /VERBOSE, _EXTRA= ]


 INPUT VARIABLES
       alt  : altitude (in degrees) [scalar or vector]
       az   : azimuth angle (in degrees, measured EAST from NORTH, but see
              keyword WS below.) [scalar or vector]
       JD   : Julian Date [scalar or vector], double precision

       Note: if RA and DEC are arrays, then alt and az will also be arrays.
             If RA and DEC are arrays, JD may be a scalar OR an array of
              the same dimensionality.

 OPTIONAL INPUT KEYWORDS:
       lat   : north geodetic latitude of location in degrees
       lon   : EAST longitude of location in degrees
               (Specify west longitude with a negative sign.)
       /WS   : Set this to get the azimuth measured westward from south
               (not East of North).
       obsname   : Set this to a valid observatory name to be used by the
               astrolib OBSERVATORY procedure, which will return the latitude
               and longitude to be used by this program.
       /B1950  : Set this if your ra and dec are specified in B1950,
               FK4 coordinates (instead of J2000, FK5)
       precess_ : Set this to 1 to force precession [default], 0 for no
                 precession.
       nutate_  : Set this to 1 to force nutation [default], 0 for no nutation.
       aberration_ : Set this to 1 to force aberration correction [default],
                 0 for no correction.
       refract_  : Set to 1 to force refraction correction [default], 0 for
                   no correction.
       altitude: The altitude of the observing location, in meters. [default=0].
       /verbose: Set this for verbose output.  The default is verbose=0.
   _extra: This is for setting TEMPERATURE or PRESSURE explicitly, which are
           used by CO_REFRACT to calculate the refraction effect of the
           atmosphere. If you don't set these, the program will make an
           intelligent guess as to what they are (taking into account your
            altitude).  See CO_REFRACT for more details.

 OUTPUT VARIABLES
       ra   : Right Ascension of object  (J2000) in degrees (FK5); scalar or
              vector.
       dec  : Declination of object (J2000) in degrees (FK5), scalar or vector.
       ha   : hour angle (in degrees) (optional)

 DEPENDENCIES:
       NUTATE, PRECESS, ADSTRING(), SUNPOS, OBSERVATORY (from the astrolib)
       CO_NUTATE, CO_ABERRATION, CO_REFRACT, HADEC2ALTAZ

 BASIC STEPS
   Precess Ra-Dec to current equinox.
   Nutation Correction to Ra-Dec
   Aberration correction to Ra-Dec
   Calculate Local Mean Sidereal Time
   Calculate Local Apparent Sidereal Time
   Calculate Hour Angle
   Do Spherical Trig to find Apparent Alt-Az
   Apply refraction correction to find observed Alt.

CORRECTIONS I DO NOT MAKE:
   *  Deflection of Light by the sun due to GR. (typically milliarcseconds,
        can be arcseconds within one degree of the sun)
   *  The Effect of Annual Parallax (typically < 1 arcsecond)
   *  and more (see below)

 TO DO
    * Better Refraction Correction.  Need to put in wavelength dependence,
       and integrate through the atmosphere.
    * Topocentric Parallax Correction (will take into account elevation of
          the observatory)
    * Proper Motion (but this will require crazy lookup tables or something).
    * Difference between UTC and UT1 in determining LAST -- is this important?
    * Effect of Annual Parallax (is this the same as topocentric Parallax?)
    * Polar Motion
    * Better connection to Julian Date Calculator.

 EXAMPLE:

   You are at Kitt Peak National Observatory, looking at a star at azimuth
   angle 264d 55m 06s and elevation 37d 54m 41s (in the visible).  Today is
   Dec 25, 2041 and the local time is 10 PM precisely.  What is the ra and dec
   (J2000) of the star you're looking at?   The temperature here is about 0
   Celsius, and the pressure is 781 millibars.    The Julian date for this
   time is 2466879.7083333

  IDL> hor2eq, ten(37,54,41), ten(264,55,06), 2466879.7083333d, ra, dec, $
           /verb, obs='kpno', pres=781.0, temp=273.0

 The program produces this output (because the VERBOSE keyword was set):

 Latitude = +31 57 48.0   Longitude = *** 36  0.0   ; longitude prints weirdly b/c of negative input to ADSTRING!!
 Julian Date =  2466879.708333
 Az, El =  17 39 40.4  +37 54 41.0   (Observer Coords)
 Az, El =  17 39 40.4  +37 53 39.6   (Apparent Coords)
 LMST = +03 53 54.1
 LAST = +03 53 53.6
 Hour Angle = +03 38 30.1  (hh:mm:ss)
 Ra, Dec:  00 15 23.5  +15 25  1.9   (Apparent Coords)
 Ra, Dec:  00 15 24.2  +15 25  0.1   (J2041.9841)
 Ra, Dec:  00 13 14.1  +15 11  0.3   (J2000)

 The star is therefore Algenib!  Compare the derived Ra, Dec with what XEPHEM
 got:
 Ra, Dec:      00 13 14.2  +15 11  1.0   (J2000)

 AUTHOR:
   Chris O'Dell
       Univ. of Wisconsin-Madison
   Observational Cosmology Laboratory
   Email: odell@cmb.physics.wisc.edu
 REVISION HISTORY:
     Made all integers type LONG  W. Landsman   September 2007
     Fixed for case of scalar Julian date but vector positions W L June 2009

(See $IDLUTILS_DIR/goddard/pro/astro/hor2eq.pro)

HOST_TO_IEEE

 NAME:
     HOST_TO_IEEE
 PURPOSE:
     Translate an IDL variable from host to IEEE representation 
 EXPLANATION:
     The variable is converted from the format used by the host architecture
     into IEEE-754 representation ("big endian" as used, e.g., in FITS data ).

     Duplicates most of the functionality of the SWAP_ENDIAN_INPLACE procedure
     with the addition of the IDLTYPE keyword.
 CALLING SEQUENCE:
     HOST_TO_IEEE, data, [ IDLTYPE = ]

 INPUT-OUTPUT PARAMETERS:
     data - any IDL variable, scalar or vector.   It will be modified by
             HOST_TO_IEEE to convert from host to IEEE representation.  Byte 
             and string variables are returned by HOST_TO_IEEE unchanged

 OPTIONAL KEYWORD INPUTS:
     IDLTYPE - scalar integer (1-15) specifying the IDL datatype according
               to the code given by the SIZE function.      This keyword
               will usually be used when supplying a byte array that needs
               to be interpreted as another data type (e.g. FLOAT).

 EXAMPLE:
     Suppose FITARR is a 2880 element byte array to be converted to a FITS
     record and interpreted a FLOAT data.

       IDL> host_to_ieee, FITARR, IDLTYPE = 4

 METHOD:
     The BYTEORDER procedure is called with the appropriate keywords

 MODIFICATION HISTORY:
      Adapted from CONV_UNIX_VAX, W. Landsman   Hughes/STX    January, 1992
      Version for IDL V5.0  August 1997
      Converted to IDL V5.0   W. Landsman   September 1997
      Added new integer datatypes  C. Markwardt/W. Landsman  July 2000
      Use /SWAP_IF_LITTLE_ENDIAN keyword for 64bit types W. Landsman Feb 2003
      Do not use XDR keywords to BYTEORDER for much improved speed
                               W. Landsman   April 2006

(See $IDLUTILS_DIR/goddard/pro/misc/host_to_ieee.pro)

HPRECESS

 NAME:
       HPRECESS
 PURPOSE:
       Precess the astrometry in a FITS header to a new equinox

 CALLING SEQUENCE:
       HPRECESS, HDR, [ yearf ]      

 INPUT-OUTPUT:
       HDR - FITS Header, must contain the CRVAL astrometry keywords,
               and either an EPOCH or EQUINOX keyword.
               HDR will be modified to contain the precessed astrometry

 OPTIONAL INPUT:
       YEARF - Scalar, giving the year of the new (Final) equinox.
               If not supplied, user will be prompted for this value.

 METHOD:
       The CRVAL and CD (or CROTA) keywords are extracted from the header 
       and precessed to the new equinox.  The EPOCH or EQUINOX keyword in 
       the header is  updated.  A HISTORY record is added

 RESTRICTIONS:
       The FK5 reference frame is assumed for both equinoxes.

 PROCEDURES USED:
       EXTAST, GET_EQUINOX(), SXADDPAR, SXADDHIST, PRECESS, PRECESS_CD
       PUTAST, ZPARCHECK
 REVISION HISTORY:                                               
       Written  W. Landsman        STX              July, 1988
       CD matrix precessed -                        February, 1989
       Update EQUINOX keyword when CROTA2 present   November, 1992
       Recognize a GSSS header                      June, 1994
       Additional Noparams value recognize for storing CDs.  RSH, 6 Apr 95
       Understand reversed X,Y (X-Dec, Y-RA) axes,   W. Landsman  October 1998
       Correct algorithm when CROTA2 is in header W. Landsman  April 2006
       Correct sign error introduced April 2006, include CDELT values
         when computing rotation of pole   W. Landsman July 2007
       Call hprecess/jprecess for 1950<>2000   W. L. Aug 2009

(See $IDLUTILS_DIR/goddard/pro/astrom/hprecess.pro)

HPRINT

 NAME:
       HPRINT
 PURPOSE:
       Display a FITS header (or other string array) 
 EXPLANATION:
       On a GUI terminal, the string array is displayed using XDISPSTR.    
       If printing at a non-GUI terminal, the string array is  printed 1 line 
       at a  time, to make sure that each element of the string array is 
       displayed on a separate line. 

 CALLING SEQUENCE:
       HPRINT, h, [ firstline ]

 INPUTS:
       H - FITS header (or any other string array).

 OPTIONAL INPUT:
       FIRSTLINE - scalar integer specifying the first line to begin 
               displaying.   The default is FIRSTLINE = 1, i.e. display 
               all the lines.     If Firstline is negative, then the first
               line to be printed is counted backward from the last line.

 NOTES:
       When displaying at the terminal, HPRINT has the following differences 
       from the intrinsic PRINT procedure

       (1) Arrays are printed one line at a time to avoid a space between 80
               character lines
       (2) Lines are trimmed with STRTRIM before being printed to speed up 
               display
       (3) The /more option is used for output. 

 EXAMPLE:
       Read the header from a FITS file named 'test.fits' and display it at the
       terminal beginning with line 50

       IDL> h = headfits( 'test.fits')         ;Read FITS header
       IDL> hprint, h, 50                      ;Display starting at line 50

       To print the last 25 lines of the header

       IDL> hprint, h, -25

 REVISION HISTORY:
       Written W. Landsman                     July, 1990
       Added test for user quit                July, 1991
       Added optional FIRSTLINE parameter      November, 1992
       Modified for when STDOUT is not a TTY W. Landsman  September 1995
       Converted to IDL V5.0   W. Landsman   September 1997
       Fixed printing in IDLDE, C. Gehman      August, 1998
       Skip PRINTF if IDL in demo mode  W. Landsman  October 2004
       Fixed bug on non-terminals, William Thompson, 18-Oct-2004
       Assume since V5.4 Use BREAK instead of GOTO  W. Landsman Apr 2006
       Call XDISPSTR on a GUI terminal  W. Landsman Jun 2006

(See $IDLUTILS_DIR/goddard/pro/misc/hprint.pro)

HREBIN

 NAME:
    HREBIN
 PURPOSE:
    Expand or contract a FITS image using (F)REBIN and update the header 
 EXPLANATION:
    If the output size is an exact multiple of the input size then REBIN is 
    used, else FREBIN is used.     User can either overwrite the input array,
    or write to new variables.

 CALLING SEQUENCE:
    HREBIN, oldhd        ;Special calling sequence to just update header
    HREBIN, oldim, oldhd, [ newim, newhd, newx, newy, OUTSIZE = ,/SAMPLE, 
                            ERRMSG =  ]

 INPUTS:
    OLDIM - the original image array
    OLDHD - the original image FITS header, string array

 OPTIONAL INPUTS:
    NEWX - size of the new image in the X direction, integer scalar
    NEWY - size of the new image in the Y direction, integer scalar
            HREBIN will prompt for NEWX and NEWY if not supplied

 OPTIONAL OUTPUTS:
    NEWIM - the image after expansion or contraction with REBIN
    NEWHD - header for newim containing updated astrometry info
            If output parameters are not supplied, the program will modify
            the input parameters OLDIM and OLDHD to contain the new array and 
            updated header.

 OPTIONAL INPUT KEYWORDS:
    /SAMPLE - Expansion or contraction is done using REBIN which uses 
              bilinear interpolation when magnifying and boxaveraging when 
              minifying.   If the SAMPLE keyword is supplied and non-zero, 
              then nearest neighbor sampling is used in both cases.   Keyword
              has no effect when output size is not a multiple of input size.

    OUTSIZE - Two element integer vector which can be used instead of the
             NEWX and NEWY parameters to specify the output image dimensions

    ALT - Single character 'A' through 'Z' or ' ' specifying which astrometry
          system to modify in the FITS header.    The default is to use the
          primary astrometry of ALT = ' '.    See Greisen and Calabretta (2002)
          for information about alternate astrometry keywords.
 OPTIONAL KEYWORD OUTPUT:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               
 PROCEDURE:
     The parameters BSCALE, NAXIS1, NAXIS2, CRPIX1, and CRPIX2 and the CD 
     (or CDELT) parameters are updated for the new FITS header.

 EXAMPLE:
     Compress a 2048 x 2048 image array IM, with FITS header HDR, to a 
     724 x 724 array.   Overwrite the input variables with the compressed 
     image and header.

     IDL> hrebin, im, hdr, OUT = [724, 724]

 PROCEDURES USED:
     CHECK_FITS, EXTAST, FREBIN, GSSS_STDAST, STRN(), SXPAR(), SXADDHIST, 
     SXADDPAR, ZPARCHECK

 MODIFICATION HISTORY:
     Written, December 1990  W. Landsman, ST System Corp.
     Update CD1_1 keywords   W. Landsman   November 1992
     Check for a GSSS header   W. Landsman  June 1994
     Update BSCALE even if no astrometry present   W. Landsman  May 1997
     Converted to IDL V5.0   W. Landsman   September 1997
     Use FREBIN to accept sizes that are not a integer multiple of the original
         size    W. Landsman     August 1998
     Correct for "edge" effects when expanding with REBIN W. Landsman Apr. 1999
     Fixed initialization of header only call broken in Apr 98 change May. 1999
     Remove reference to obsolete !ERR  W. Landsman   February 2000
     Use double precision formatting for CD matrix W. Landsman April 2000
     Recognize PC00n00m astrometry format   W. Landsman   December 2001
     Correct astrometry for integral contraction W. Landsman  April 2002
     Fix output astrometry for non-equal plate scales for PC matrix or
     CROTA2 keyword, added ALT keyword.   W. Landsman May 2005
     Update distortion parameters if present  W. Landsman August 2007
     Don't update BSCALE/BZERO for unsigned integer W.Landsman Mar 2008
     Use post-V6.0 notation   W. Landsman  Nov 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/hrebin.pro)

HREVERSE

 NAME:
       HREVERSE
 PURPOSE:
       Reverse an image about either dimension and update FITS astrometry
 EXPLANATION:
       Reverse an image about either the X or Y axis, and create a new 
       header with updated astrometry for the reversed image.

 CALLING SEQUENCE:
       HREVERSE,oldim,oldhd, [ subs, /SILENT ]   ;Update input image and header
               or
       HREVERSE, oldim, oldhd, newim, newhd, [ subs, /SILENT ]   

 INPUTS:
       OLDIM - the original image array
       OLDHD - the original image header

 OPTIONAL INPUTS:
       SUBS - Subs equals 1 to reverse the order of the X dimension,
               2 to reverse Y order.  If omitted, then HREVERSE will
               prompt for this scalar parameter.

 OPTIONAL OUTPUTS:
       NEWIM - the rotated image, with the same dimensions as Oldim 
       NEWHD - header for newim containing updated astrometry info
               If output parameters are not supplied, the program
               will modify the input parameters OLDIM and OLDHD
               to contain the rotated image and updated header.

 OPTIONAL KEYWORD INPUT:
       SILENT - if set and non-zero, then informative messages are suppressed.

 OPTIONAL KEYWORD OUTPUT:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               

 SIDE EFFECTS:
       A right-handed coordinate system is converted into a left-
       handed one, and vice-versa.

 PROCEDURE:
       The User's Library procedure REVERSE is used to reverse the image.
       The CD and CRPIX header parameters are updated for the new header.
       For AIPS type astrometry, the CDELT parameters are also updated.
       A history record is also added to the header

 PROCEDURES USED:
       CHECK_FITS, EXTAST, REVERSE(), STRN(), SXADDPAR 
 MODIFICATION HISTORY:
       Written, Aug. 1986 W. Landsman, STI Corp.
       Error modifying CROTA angles corrected     9-23-88
       Added format keyword, J. Isensee, July, 1990
       Work for ST Guide Star images, W. Landsman   HSTX, May 1995
       Compute CRPIX1 correctly for X reversal   W. Landsman HSTX August 1995
       Converted to IDL V5.0   W. Landsman   September 1997
       Added ERRMSG, Use double precision formatting, W. Landsman April 2000
       Recognize PC00n00m astrometry matrix   W. Landsman   December 2001

(See $IDLUTILS_DIR/goddard/pro/astrom/hreverse.pro)

HROT

 NAME:
       HROT
 PURPOSE:
       Rotate an image and create new FITS header with updated astrometry.
 EXPLANATION: 
       Cubic, bilinear or nearest neighbor interpolation can be used.

 CALLING SEQUENCE:
       HROT, oldim, oldhd, [ newim, newhd, angle, xc, yc, int, 
                       MISSING =, INTERP =, CUBIC = , /PIVOT]
 INPUTS:
       OLDIM - the original image array                             
       OLDHD - the original FITS image header, string array

 OPTIONAL INPUTS:
       NEWIM - If NEWIM is set to -1, then the old image and header will
               be updated
       ANGLE - Rotation angle, degrees clockwise, scalar
       XC    - X Center of rotation (-1 for center of image)
       YC    - Y Center of rotation (-1 for center of image)
       INT   - 0 for nearest neighbor, 1 for bilinear interpolation
               2 for cubic interpolation.  

 OPTIONAL OUTPUTS:
       NEWIM - the rotated image, with the same dimensions as Oldim 
       NEWHD - header for newim containing updated astrometry info
               If output parameters are not supplied, the program
               will modify the input parameters OLDIM and OLDHD
               to contain the rotated image and updated header.

 OPTIONAL INPUT KEYWORD:
       MISSING - Set this keyword to a scalar value which will be assigned
               to pixels in the output image which do not correspond to 
               existing input images (e.g if one rotates off-center). 
               If not supplied then linear extrapolation is used.
               ***NOTE: A bug was introduced into the POLY_2D function in IDL
               V5.5 (fixed in V6.1) such that the MISSING keyword
               may not work properly with floating point data***

       INTERP - scalar set to either 0 (nearest neighbor interpolation),
               1 (bilinear interpolation), or 2 (cubic interpolation).    
               The interpolation type can be specified by either the INTERP 
               keyword or the int parameter
             
       CUBIC - If set and non-zero then cubic interpolation is used (see ROT),
               which is equivalent to setting INT = 2.   In IDL V5.0 and later,
                this keyword can also be set to a value between -1 and 0.

       /PIVOT - Setting this keyword causes the image to pivot around the point
		XC, YC, so that this point maps into the same point in the
		output image.  If this keyword is set to 0 or omitted, then the
		point XC, YC in the input image is mapped into the center of
		the output image.

 OPTIONAL OUTPUT KEYWORD:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               
 EXAMPLE:
       Rotate an image non-interactively 30 degrees clockwise.  Use
       bilinear interpolation, and set missing values to 0.

       IDL>  HROT, im_old, h_old, im_new, h_new, 30, -1, -1, 1, MIS = 0

       As above but update the input image and header and pivot about (100,120)

       IDL>  HROT, im_old, h_old, -1, -1, 30, 100, 120, 1, MIS = 0, /PIVOT
 RESTRICTIONS:
       Unlike the ROT procedure, HROT cannot be used to magnify or
       or demagnify an image. Use HCONGRID or HREBIN instead.

 PROCEDURE:
       The image array is rotated using the ROT procedure.
       The CD (or CROTA) and CRPIX parameters, if present in the FITS header,
       are updated for the new rotation.
       History records are also added to the header

 PROCEDURES USED:
       CHECK_FITS, EXTAST, GETOPT(), GETROT, ROT(), STRN(), SXADDPAR

 MODIFICATION HISTORY:
       Written, Aug. 1986 W. Landsman, ST Systems Corp.
       Added MISSING keyword, W. Landsman March, 1991
       Added cubic interpolation, use astrometry structure   Feb 1994
       Removed call to SINCE_VERSION()  W. Landsman  March 1996
       Assume at least V3.5, add CUBIC parameter       W. Landsman  March 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Fix for CROTA2 defined and CDELT1 NE CDELT2, W. Landsman  November 1998
       Fix documentation  to specify clockwise rotation W. Landsman Dec. 1999
       Added /PIVOT keyword    W. Landsman  January 2000
       Added ERRMSG, Use double precision formatting, W. Landsman April 2000
       Consistent conversion between CROTA and CD matrix W. Landsman Oct 2000
       Work for both CD001001 and CDELT defined  W. Landsman   March 2001
       Recognize PC matrix astrometry  W. Landsman December 2001
       Update astrometry correctly when /PIVOT applied W. Landsman March 2002
       Update CROTA2 astrometry correctly, approximate GSSS W.L. June 2003
       Work with CD1_1, PC1_1 and CROTA keywords W. L. July 2003 
       Work with angle as a 1 element vector  W.L.  May 2006

(See $IDLUTILS_DIR/goddard/pro/astrom/hrot.pro)

HROTATE

 NAME:
     HROTATE
 PURPOSE:
     Apply the IDL ROTATE function and update astrometry in a FITS header
 EXPLANATION:
     Apply the intrinsic IDL ROTATE function to an image and update 
     astrometry in the associated FITS header.

 CALLING SEQUENCE:
     HROTATE, oldim, oldhd, newim, newhd, direction
               or
     HROTATE, oldim, oldhd, direction 
                       
 INPUTS:
     OLDIM - the original image array                             
     OLDHD - the original FITS image header, string array
     DIRECTION - Scalar integer (0-7) specifying rotation direction, 
               exactly as specified by the IDL ROTATE function.

        Direction  Transpose?  Rot. CCW  X1  Y1 
       ---------------------------------------- 
       0          No          None     X0  Y0    (no change)
       1          No          90      -Y0  X0 
       2          No          180     -X0 -Y0 
       3          No          270      Y0 -X0 
       4          Yes         None     Y0  X0 
       5          Yes         90      -X0  Y0                   
       6          Yes         180     -Y0 -X0 
       7          Yes         270      X0 -Y0 

 OPTIONAL OUTPUTS:
     NEWIM - the rotated image, with the same dimensions as Oldim 
     NEWHD - header for newim containing updated astrometry info
               If output parameters are not supplied, the program
               will modify the input parameters OLDIM and OLDHD
               to contain the rotated image and updated header.

 OPTIONAL KEYWORD OUTPUT:
     ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               
 EXAMPLE:
     Rotate an image exactly 90 degrees counterclockwise and update the
     FITS image array and header. 

       IDL>  HROT, im, h, im_new, h_new, 1

 PROCEDURE:
      The image array is rotated using the ROTATE function.
      The CD (or CROTA) and CRPIX parameters, if present in the FITS header,
      are updated for the new rotation.
      History records are also added to the header

 RESTRICTIONS: 
     Does not work Guide Star Survey (GSS) astrometry.    Use GSSS_STDAST to
     first convert 
 PROCEDURES USED:
     CHECK_FITS(), SXADDPAR, EXTAST

 MODIFICATION HISTORY:
     Written,  Mar 1997    W. Landsman,  Hughes STX
     Work for non-square images   W. Landsman   June 1998 Raytheon STX
     Fix for different plate scales, and CROTA2 defined, November 1998  
     Added ERRMSG, Use double precision formatting, W. Landsman April 2000
     Consistent conversion between CROTA and CD matrix W. Landsman Oct 2000
     Correct update when CROTA keyword present W. Landsman  June 2003
     Update CDELT for AIPS-style astrometry headers M. Perrin/WL Jul 2003
     Convert GSS astrometry to WCS W. Landsman  November 2004
     Work even if no astrometry present, just update NAXIS* WL June 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/hrotate.pro)

IEEE_TO_HOST

 NAME:
     IEEE_TO_HOST
 PURPOSE:
     Translate an IDL variable from IEEE-754 to host representation 
 EXPLANATION:
     The variable is translated from IEEE-754 ("big-endian" as used, for
     example, in FITS data ), into the host machine architecture.

     Duplicates most of the functionality of the SWAP_ENDIAN_INPLACE procedure
     introduced in V5.6, with the addition of the IDLTYPE keyword.
 CALLING SEQUENCE:
     IEEE_TO_HOST, data, [ IDLTYPE = , ]

 INPUT-OUTPUT PARAMETERS:
     data - any IDL variable, scalar or vector.   It will be modified by
             IEEE_TO_HOST to convert from IEEE to host representation.  Byte 
             and string variables are returned by IEEE_TO_HOST unchanged

 OPTIONAL KEYWORD INPUTS:
     IDLTYPE - scalar integer (1-15) specifying the IDL datatype according
               to the code given by the SIZE function.     This keyword
               is usually when DATA is a byte array to be interpreted as
               another datatype (e.g. FLOAT).

 EXAMPLE:
       A 2880 byte array (named FITARR) from a FITS record is to be 
       interpreted as floating and converted to the host representaton:

       IDL> IEEE_TO_HOST, fitarr, IDLTYPE = 4     

 METHOD:
       The BYTEORDER procedure is called with the appropriate keyword

 MODIFICATION HISTORY:
      Written, W. Landsman   Hughes/STX   May, 1992
      Converted to IDL V5.0   W. Landsman   September 1997
      Under VMS check for IEEE -0.0 values   January 1998
      VMS now handle -0.0 values under IDL V5.1    July 1998
      Added new integer datatypes  C. Markwardt/W. Landsman  July 2000
      Post-V5.1 version, no VMS negative zero check  W. Landsman July 2001
      Use size(/type)  W. Landsman December 2002
      Use /SWAP_IF_LITTLE_ENDIAN keyword for 64bit types W. Landsman Feb 2003
      Do not use XDR keywords to BYTEORDER for much improved speed
                               W. Landsman   April 2006
      Update cosmetic typo for structures W. Landsman  October 2006

(See $IDLUTILS_DIR/goddard/pro/misc/ieee_to_host.pro)

IMAGE_DIMENSIONS

 The purpose of this function is to return the various dimensions of the image,
 and also to extract relevant image information via output keywords. The
 function works only with 2D and 3D (24-bit) images, with or without alpha
 channels.
   
 :Categories:
    Utilities
    
 :Returns:
     A vector containing the size of each dimension of the image. It is equivalent
     to calling the SIZE function with the DIMENSIONS keyword set.
       
 :Params:
    image:  in, optional, type=various
        The image variable from which information is to be obtained.
       
 :Keywords:
     alphachannel: out, optional, type=boolean
        This keyword is set to 1 if there is an alpha channel in the image. Otherwise,
        the keyword is set to 0. 
     trueindex: out, optional, type=integer
        The position of the "true color" index in the return value. Is -1 for 2D images.
     xindex: out, optional, type=integer
        The index (position) of the X dimension in the return value.
     xsize: out, optional, type=integer
        The X size of the image.
     yindex: out, optional, type=integer
        The index (position) of the Y dimension in the return value.
     ysize: out, optional, type=integer
        The Y size of the image.
        
 :Examples:
    To load open a window of the appropriate size and display a 24-bit image::

       dims = Image_Dimensions(image24, XSize=xsize, YSize=ysize, TrueIndex=trueindex)
       Window, XSIZE=xsize, YSIZE=ysize
       TV, image24, TRUE=trueindex
       
 :Author:
    FANNING SOFTWARE CONSULTING::
        David W. Fanning 
        1645 Sheely Drive
        Fort Collins, CO 80526 USA
        Phone: 970-221-0438
        E-mail: david@idlcoyote.com
        Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 :History:
    Modification History::
       Written by:  David W. Fanning, 5 March 2003.
       Added support for alpha channel images, include ALPHACHANNEL keyword. 13 May 2009. DWF.

 :Copyright:
     Copyright (c) 2003-2011, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/image_dimensions.pro)

IMCONTOUR

 NAME:
       IMCONTOUR
 PURPOSE:
       Make a contour plot labeled with astronomical coordinates.
 EXPLANATION:
       The type of coordinate display is controlled by the keyword TYPE
       Set TYPE=0 (default) to measure distances from the center of the image
       (IMCONTOUR will decide whether the plotting units will be in
       arc seconds, arc minutes, or degrees depending on image size.)
       Set /TYPE for standard RA and Dec labeling

       By using the /NODATA keyword, IMCONTOUR can also be used to simply
       provide astronomical labeling of a previously displayed image.
 CALLING SEQUENCE
       IMCONTOUR, im, hdr,[ /TYPE, /PUTINFO, XDELTA = , YDELTA =, _EXTRA = 
                            XMID=, YMID= ]

 INPUTS:
       IM - 2-dimensional image array
       HDR - FITS header associated with IM, string array, must include
               astrometry keywords.   IMCONTOUR will also look for the
               OBJECT and IMAGE keywords, and print these if found and the 
               PUTINFO keyword is set.

 OPTIONAL PLOTTING KEYWORDS:
       /TYPE - the type of astronomical labeling to be displayed.   Either set
               TYPE = 0 (default), distance to center of the image is
               marked in units of Arc seconds, arc minutes, or degrees

               TYPE = 1 astronomical labeling with Right ascension and 
               declination.

       /PUTINFO - If set, then IMCONTOUR will add information about the image
               to the right of the contour plot.  Information includes image
               name, object, image center, image center, contour levels, and
               date plot was made

       XDELTA, YDELTA - Integer scalars giving spacing of labels for TYPE=1.  
               Default is to label every major tick (XDELTA=1) but if 
               crowding occurs, then the user might wish to label every other
               tick (XDELTA=2) or every third tick (XDELTA=3)

       XMID, YMID - Scalars giving the X,Y position from which offset distances
               will be measured when TYPE=0.   By default, offset distances 
               are measured from the center of the image.
       /OVERLAY - If set, then IMCONTOUR is assumed to overlay an image.
               This requires 1 extra pixel be included on the X and Y axis,
               to account for edge effects in the image display.    Setting
               OVERLAY provide a better match of the contour and underlying
               image but is not as aesthetically pleasing because the contours
               will not extend to the axes. 
               

       Any keyword accepted by CONTOUR may also be passed through IMCONTOUR
       since IMCONTOUR uses the _EXTRA facility.     IMCONTOUR uses its own
       defaults for the XTITLE, YTITLE XMINOR, YMINOR, and SUBTITLE keywords
       but these may be overridden.    Note in particular the /NODATA keyword
       which can be used if imcontour.pro is to only provide labeling.

 NOTES:
       (1) The contour plot will have the same dimensional ratio as the input
           image array
       (2) To contour a subimage, use HEXTRACT before calling IMCONTOUR
       (3) Use the /NODATA keyword to simply provide astronomical labeling
           of a previously displayed image.
       (4) The IMCONTOUR display currently does not indicate the image 
           rotation in any way, but only specifies coordinates along the 
           edges of the image 

 EXAMPLE:
       Overlay the contour of an image, im2, with FITS header, h2, on top
       of the display of a different image, im1.   Use RA, Dec labeling, and
       seven equally spaced contour levels.    The use of a program like
       David Fanning's cgImage  http://www.idlcoyote.com/programs/cgimage.pro
       is suggested to properly overlay plotting and image coordinates.  The
       /Keep_aspect_ratio keyword must be used.

       IDL> cgimage,im1,/keep_aspect, position = pos
       IDL> imcontour,im2,h2,nlevels=7,/Noerase,/TYPE,position = pos

 PROCEDURES USED:
       CHECK_FITS, EXTAST, GETROT, TICPOS, TICLABEL, TIC_ONE, TICS, XYAD
       CONS_RA(), CONS_DEC(), ADSTRING()

 REVISION HISTORY:
       Written   W. Landsman   STX                    May, 1989
       Fixed RA,Dec labeling  W. Landsman             November, 1991
       Fix plotting keywords  W.Landsman             July, 1992
       Recognize GSSS headers  W. Landsman            July, 1994
       Removed Channel keyword for V4.0 compatibility June, 1995
       Add _EXTRA CONTOUR plotting keywords  W. Landsman  August, 1995
       Add XDELTA, YDELTA keywords  W. Landsman   November, 1995
       Use SYSTIME() instead of !STIME                August, 1997
       Remove obsolete !ERR system variable W. Landsman   May 2000 
       Added XMID, YMID keywords to specify central position (default is still
          center of image)  W. Landsman               March 2002     
       Recognize Galactic coordinates, fix Levels display when /PUTINFO set
           W. Landsman                May 2003
       Correct conversion from seconds of RA to arcmin is 4 not 15.
       	M. Perrin					July 2003
       Fix integer truncation which appears with tiny images WL  July 2004
       Changed some keyword_set() to N_elements WL  Sep 2006
       Work to 1 pixels level when overlaying an image,added /OVERLAY keyword
        Use FORMAT_AXIS_VALUES()  W. Landsman   Jan 2008 
       Make /OVERLAY  always optional   W. Landsman  Feb 2008
       Check if RA crosses 0 hours  WL  Aug 2008
       Use Coyote Graphics WL Feb 2011

(See $IDLUTILS_DIR/goddard/pro/astro/imcontour.pro)

IMDBASE

 NAME:
     IMDBASE
 PURPOSE:
     Find the sources in an IDL database that are located on a given image.

 CALLING SEQUENCE:
    imdbase, hdr, [catalogue, list, ALT=, XPOS= ,YPOS=, XRANGE= ,YRANGE= , 
                       SUBLIST =, /SILENT ]  

 INPUTS:
    hdr - FITS image header containing astrometry, and the NAXIS1,
               NAXIS2 keywords giving the image size
    catalogue - string giving name of catalogue in database.   If not supplied
              then the currently open database is used.   The database must 
              contain the (preferably indexed) fields RA (in hours) and DEC.  
              Type DBHELP for a list of the names of available catalogues.

 OPTIONAL OUTPUT PARAMETER:
    LIST - A longwprd vector containing the entry numbers of sources found
           within the image.   This vector can then be used with other
           database procedures, e.g. to print specified fields (DBPRINT)
           or subselect with further criteria (DBFIND)

 OPTIONAL OUTPUT KEYWORD PARAMETER:
     XPOS - REAL*4 vector giving X positions of catalogue sources found 
            within the image
     YPOS - REAL*4 vector giving Y positions of catalogue sources found 
            within the image

 OPTIONAL INPUT KEYWORD PARAMETERS
       ALT -  single character 'A' through 'Z' or ' ' specifying an alternate 
              astrometry system present in the FITS header.    The default is
              to use the primary astrometry or ALT = ' '.   If /ALT is set, 
              then this is equivalent to ALT = 'A'.   See Section 3.3 of 
              Greisen & Calabretta (2002, A&A, 395, 1061) for information about
              alternate astrometry keywords.
     SILENT - If set, then informational messages are suppressed
     SUBLIST - vector giving entries in the database to consider in the
               search.  If not supplied, or set equal to -1, then all entries
               are considered.
     XRANGE - 2 element vector giving the X range of the image to consider.
              The default is to search for catalogue sources within the entire
             image
     YRANGE - 2 element vector giving the Y range of the image to consider.

 NOTES:
     If an output list vector is not supplied, then the found objects are
     diplayed at the terminal.

 EXAMPLE:
      Find all existing IUE observations within the field of the FITS 
      file fuv0435fc.fits.  Subselect those taken with the SWP camera

      H = HEADFITS('fuv0435f.fits')             ;Read FITS header 
      IMDBASE,H,'IUE',list              ;Find IUE obs. within image 
      list2 = DBFIND('CAM_NO=3',list)   ;Subselect on SWP images

 SIDE EFFECTS:
      The IDL database is left open upon exiting IMDBASE.
 NOTES:
      IMDBASE checks the description of the RA item in the database for the
      string '1950'.    If found, the database RA and Dec are assumed to be 
      in equinox B1950.   Otherwise they are assumed to be in ICRS or J2000. 

 SYSTEM VARIABLES:                                                
      The non-standard system variable !TEXTOUT is required for use with the
      database procedures.   

 PROCEDURES USED:
      AD2XY, DBEXT, DB_ITEM, DB_ITEM_INFO(), DBOPEN, DBFIND(), EXTAST, 
      GET_EQUINOX(), GSSSADXY, GSSSXYAD, HPRECESS, SXPAR(), XY2AD 
 REVISION HISTORY:
      Written W. Landsman            September, 1988
      Added SUBLIST keyword          September, 1991
      Updated to use ASTROMETRY structures    J.D. Offenberg, HSTX, Jan 1993
      Conversion for precession fixed.   R.Hill, HSTX, 22-Apr-93
      Check RA description for equinox   W. Landsman  Aug 96
      Call HPRECESS if header equinox does not match DB  W. Landsman Oct. 1998
      Assume Equinox J2000 if not explicitly B1950 W. Landsman Jan. 2005
      Added ALT keyword W. Landsman  April 2005
      Use open database, if no catalogue name given  W.L  April 2008
      Added /SILENT keyword W.L. Mar 2009

(See $IDLUTILS_DIR/goddard/pro/database/imdbase.pro)

IMF

 NAME:
       IMF
 PURPOSE:
       Compute an N-component power-law logarithmic initial mass function 
 EXPLANTION:
       The function is normalized so that the total mass distribution 
       equals one solar mass.

 CALLING SEQUENCE:
       psi = IMF( mass, expon,  mass_range )

 INPUTS:
       mass - mass in units of solar masses (scalar or vector)
               Converted to floating point if necessary
       expon - power law exponent, usually negative, scalar or vector
               The number of values in expon equals the number of different
               power-law components in the IMF
               A Saltpeter IMF has a scalar value of expon = -1.35
       mass_range - vector containing the mass upper and lower limits of the 
               IMF and masses where the IMF exponent changes.   The number 
               of values in mass_range should be one more than in expon.   
               The values in mass_range should be monotonically increasing.

 OUTPUTS
       psi - mass function, number of stars per unit logarithmic mass interval
               evaluated for supplied masses

 NOTES:
       The mass spectrum f(m) giving the number of stars per unit mass 
       interval is related to psi(m) by  m*f(m) = psi(m).    The normalization
       condition is that the integral of psi(m) between the upper and lower
       mass limit is unity.

 EXAMPLE:
       (1) Print the number of stars per unit mass interval at 3 Msun 
               for a Salpeter (expon = -1.35) IMF, with a mass range from 
               0.1 MSun to 110 Msun.

               IDL> print, imf(3, -1.35, [0.1, 110] ) / 3

       (2) Lequex et al. (1981, A & A 103, 305) describes an IMF with an
               exponent of -0.6 between 0.007 Msun and 1.8 Msun, and an
               exponent of -1.7 between 1.8 Msun and 110 Msun.    Plot
               the mass spectrum f(m)

               IDL> m = [0.01,0.1,indgen(110) + 1 ]  ;Make a mass vector
               IDL> expon = [-0.6, -1.7]       ;Exponent Vector
               IDL> mass_range = [ 0.007, 1.8, 110]    ;Mass range
               IDL> plot,/xlog,/ylog, m, imf(m, expon, mass_range ) / m

 METHOD
       IMF first calculates the constants to multiply the power-law 
       components such that the IMF is continuous at the intermediate masses, 
       and that the total mass integral is one solar mass.  The IMF is then 
       calculated for the supplied masses.   Also see Scalo (1986, Fund. of
       Cosmic Physics, 11, 1)

 PROCEDURES CALLED:
       None
 REVISION HISTORY:
       Written    W. Landsman              August, 1989  
       Set masses LE mass_u rather than LT mass_u  August, 1992
       Major rewrite to accept arbitrary power-law components   April 1993
       Convert EXPON to float if necessary  W. Landsman     March 1996
       Remove call to DATATYPE, V5.3 version  W. Landsman  August 2000

(See $IDLUTILS_DIR/goddard/pro/astro/imf.pro)

IMLIST

 NAME:
      IMLIST        
 PURPOSE:
      Display pixel values on an image surrounding a specified X,Y center.
 EXPLANATION:
      IMLIST is similar to TVLIST but the center pixel is supplied directly by
      the user, rather than being read off of the image display

 CALLING SEQUENCE:
      IMLIST, Image, Xc, Yc, [ TEXTOUT = , DX = , DY = ,WIDTH = ,DESCRIP = ]

 INPUTS:
      Image - Two-dimensional array containing the image 
      Xc  -   X pixel value at which to center the display, integer scalar 
      Yc -    Y pixel value at which to center the display, integer scalar 

 OPTIONAL INPUTS KEYWORDS:
      TEXTOUT - Scalar number (1-7) or string which determines output device.
               (see TEXTOPEN) The following dev/file is opened for output.

               textout=1       TERMINAL using /more option
               textout=2       TERMINAL without /more option
               textout=3       <program>.prt
               textout=4       laser.tmp
               textout=5       user must open file
               textout=7       same as 3 but text is appended to <program>.prt
                               if file already exists
               textout = filename (default extension of .prt)

       DX     -Integer scalar giving the number of pixels inthe  X direction 
               to be displayed.  If omitted then DX = 18 for byte images, and 
               DX = 14 for integer images.  IMLIST will display REAL data 
               with more significant figures if more room is available to 
               print.  

       DY    - Same as DX, but in Y direction.  If omitted, then DY = DX 
       WIDTH - Integer scalar giving the character width of the output device.
               Default is 80 characters.
       DESCRIP =  Scalar string which will be written as a description over
               the output pixel values.   If DESCRIP is not supplied, and the
               output device specified by TEXTOUT is not a terminal, then the
               user will be prompted for a description.
       OFFSET - 2 element numeric vector giving an offset to apply to the 
               display of the X,Y coordinates of the image (e.g. if the 
               supplied image array is a subarray of a larger image).
 OUTPUTS:
       None.

 PROCEDURE:
       Corresponding region of image is then displayed at
       the terminal.   If necessary, IMLIST will divide all pixel values
       in a REAL*4 image by a (displayed) factor of 10 to make a pretty format.

 SYSTEM VARIABLES:
       If the keyword TEXTOUT is not supplied, then the non-standard system
       variable !TEXTOUT will be read.    (The procedure ASTROLIB can be
       used to add the non-standard system variables.)

 RESTRICTIONS:
       IMLIST may not be able to correctly format all pixel values if the
       dynamic range of the values near the center pixel is very large

 EXAMPLE:
       Display the pixel values of an image array IM in the vicinity of 254,111

       IDL> imlist, IM, 254, 111

 PROCEDURES USED
       TEXTOPEN, F_FORMAT(), TEXTCLOSE
 REVISION HISTORY:
       Written,    W. Landsman             June, 1991
       Added DESCRIP keyword    W. Landsman      December, 1991
       Treat LONG image as integer when possible, call TEXTOPEN with /STDOUT
       keyword, W. Landsman   April, 1996
       Use SYSTIME() instead of !STIME  August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Recognize new integer types, added OFFSET keyword  W. Landsman Jan. 2000
       Replace DATATYPE() with size(/TNAME)  W. Landsman Nov. 2001
       Handle NAN values in output display W. Landsman June 2004
       Use V6.0 notation  W. Landsman April 2011

(See $IDLUTILS_DIR/goddard/pro/image/imlist.pro)

IRAFDIR

 NAME:
	IRAFDIR
 PURPOSE:
	Provide a brief description of the IRAF images on a directory
 CALLING SEQUENCE:
	IRAFDIR, [ directory, TEXTOUT = ]

 OPTIONAL INPUT PARAMETERS:
	DIRECTORY - Scalar string giving file name, disk or directory to 
		be searched 

 OPTIONAL INPUT KEYWORD:
	TEXTOUT - specifies output device (see TEXTOPEN)
		textout=1	TERMINAL using /more option
		textout=2	TERMINAL without /more option
		textout=3	<program>.prt
		textout=4	laser.tmp
		textout=5      user must open file
		textout=7       Append to existing <program>.prt file
		textout = 'filename' (default extension of .prt)

 OUTPUT PARAMETERS:
	None

 PROCEDURE:
	FINDFILE is used to find all '.imh' files in the directory. 
	The object name and image size (NAXIS1, NAXIS2) are extracted
	from the header. Each header is also searched for the parameters
	DATE-OBS (or TDATEOBS), TELESCOP (or OBSERVAT), EXPTIME.
  
 RESTRICTIONS:
	(1) Some fields may be truncated since IRAFDIR uses a fixed format 
		output
	(2) No more than 2 dimension sizes are displayed 
 SYSTEM VARIABLES:
	If 'textout' keyword is not specified to select an output device,
	!TEXTOUT will be the default.    This non-standard system variable
	can be added using the procedure ASTROLIB.

 PROCEDURE CALLS:
	EXPAND_TILDE(), FDECOMP, REMCHAR, TEXTOPEN, TEXTCLOSE
 MODIFICATION HISTORY:
	Written, K. Venkatakrishna, ST Systems Corp, August 1991
	Work for IRAF V2.11 format   W. Landsman   November 1997
	Assume since V5.5 use file_search W. Landsman   Sep 2006

(See $IDLUTILS_DIR/goddard/pro/disk_io/irafdir.pro)

IRAFRD

 NAME:
     IRAFRD
 PURPOSE:
       Read an IRAF (.imh) file into IDL image and header arrays.
 EXPLANATION:
       The internal IRAF format changed somewhat in IRAF V2.11 to a machine
       independent format, with longer filename allocations.  This version 
       of IRAFRD should be able to read either format. 

 CALLING SEQUENCE:
       IRAFRD, im, hdr, filename, [/SILENT ]  

 OPTIONAL INPUT:
       FILENAME -  Character string giving the name of the IRAF image 
               header.  If omitted, then program will prompt for the 
               file name.  IRAFRD always assumes the header file has an 
               extension '.imh'.    IRAFRD will automatically locate the
               ".pix" file containing the data by parsing the contents of 
               the .imh file.   (If the parse is unsuccesful, then IRAFRD looks
               in the same directory as the .imh file.)
 OUTPUTS:
       IM - array containing image data
       HDR - string array containing header.  Basic information in the
               IRAF header is converted to a FITS style header

 OPTIONAL INPUT KEYWORDS:
       /SILENT  - If this keyword is set and non-zero, then messages displayed
               while reading the image will be suppressed.  

 RESTRICTIONS:
       (1)  Image size and history sections of the IRAF header are copied 
               into the FITS header HDR.  Other information (e.g. astrometry)
               might not be included unless it is also in the history section
       (2)  IRAFRD ignores the node name when deciphering the name of the
               IRAF ".pix" file.
       (3)  Certain FITS keywords ( DATATYPE, IRAFNAME) may appear more than
               once in the output name
       (4)  Does not read the DATE keyword for the new (V2.11) IRAF files
 NOTES:
       IRAFRD obtains dimensions and type of image from the IRAF header.

 PROCEDURES CALLED:
       FDECOMP, SXADDPAR, SXPAR()

 MODIFICATION HISTORY:
       Written W. Landsman, STX January 1989
       Converted to IDL Version 2.  M. Greason, STX, June 1990
       Updated for DecStation compatibility   W. Landsman   March 1992
       Don't leave an open LUN  W. Landsman   July 1993
       Don't overwrite existing OBS-DATE  W. Landsman  October 1994
       Don't bomb on very long FITS headers W. Landsman  April 1995
       Work on Alpha/OSF and Linux      W. Landsman     Dec 1995
       Remove /VMSIMG keyword, improve efficiency when physical and
               image dimensions differ   W. Landsman     April 1996
       Don't use FINDFILE (too slow)     W. Landsman     Oct 1996
       Read V2.11 files, remove some parameter checks W. Landsman Nov. 1997
       Fixed problem reading V2.11 files with long headers Jan. 1998
       Accept names with multiple extensions    W. Landsman   April 98 
       Test for big endian machine under V2.11 format W. Landsman Feb. 1999
       Don't read past the end of file for V5.4 compatilibity  W.L.  Jan. 2001
       Convert to square brackets W.L   May 2001
       Assume since V5.4, remove SPEC_DIR()   W. L.   April 2006

(See $IDLUTILS_DIR/goddard/pro/disk_io/irafrd.pro)

IRAFWRT

 NAME:
     IRAFWRT
 PURPOSE:
     Write IDL data in IRAF (OIF) format (.imh and .pix files).
 EXPLANATION:
     Does the reverse of IRAFRD.    IRAFWRT writes the "old" IRAF format
     used prior to v2.11.   However, this "old" format is still readable by
     the current version of IRAF.

 CALLING SEQUENCE: 
    IRAFWRT, image, hdr, filename, [ PIXDIR = ]

 INPUTS:
     image - array containing data
     hdr   - The  corresponding FITS header.   Use MKHDR to create a minimal
             FITS header if one does not already exist.
     filename - Scalar string giving the name of the file to be written 
             Should not include the extension name, which will be supplied 
             by IRAFWRT.
 OUTPUTS:
     None

 OPTIONAL KEYWORD INPUT:
      PIXDIR - scalar string specifying the directory into which to write
              the IRAF pixel (.pix) file.   The default is to write the pixel
              file to the same directory as the header (.imh) file

 SIDE EFFECTS:
      Image array and  FITS header are written to IRAF pixel file 
               'filename'.pix and header file 'filename'.imh

 EXAMPLE:
       Write an empty 50 x 50 array of all zeros to an IRAF file named 'EMPTY'

       IDL> im = intarr( 50, 50)         ;Create empty array
       IDL> mkhdr, hdr, im               ;Create a minimal FITS header
       IDL> irafwrt, im, hdr, 'empty'    ;Write to a IRAF file named 'empty'

 PROCEDURE:
       IRAFWRT gets information about the data - image dimensions, size, 
       datatype, maximum and minimum pixel values - and writes it into
       the binary part of the header. The ASCII part of the header
       is directly copied after deleting records with certain keywords 
       A pixel file is created, with a header in the first 1024 bytes

 RESTRICTIONS:
       (1) The files are not created by IRAFWRT are not identical to those 
               created by the IRAF routine rfits.    However, the files 
               created by IRAFWRT appear to be compatible with all the IRAF 
               routines tested so far.
       (2)  IRAFWRT has been tested on a limited number of data types
       (3)  IRAFWRT has only been tested on Unix and VMS systems.

 PROCEDURES CALLED:
       FDECOMP, IS_IEEE_BIG(), ISARRAY(), REPCHR(), STRN(), SXDELPAR, SXPAR()
 MODIFICATION HISTORY:
       Written K. Venkatakrishna, STX February 1992
       VMS compatibility    W. Landsman      April 1992
       Work with headers without DATE-OBS or ORIGIN           August 1992
       Preserve HISTORY records with other FITS records       March 1995    
       Fix case where a minimal FITS header supplied          August 1995
       Work under Alpha/OSF and Linux                         Dec.   1995
       Make sureheader has 80 char lines, use IS_IEEE_BIG()   May    1997
       Don't apply strlowcase to .pix name   W. Landsman      April 1999
       Work with double precision            W. Landsman      May 1999
       Minimize use of obsolete !ERR         W. Landsman      Feb. 2000
       Assume since V5.5, remove VMS support W. Landsman       Sep. 2006

(See $IDLUTILS_DIR/goddard/pro/disk_io/irafwrt.pro)

ISARRAY

 NAME:
       ISARRAY
 PURPOSE:
       Tests if the argument is an array.
 CATEGORY:
 CALLING SEQUENCE:
       flag = isarray(a)
 INPUTS:
       a = variable to test.                                in
 KEYWORD PARAMETERS:
 OUTPUTS:
       flag = test result: 0 if not array, else non-zero.   out
 COMMON BLOCKS:
 NOTES:
 MODIFICATION HISTORY:
       R. Sterner  20 Mar, 1986.
       Checked for undefined variables.  RES 25 Aug, 1989.
       Johns Hopkins Applied Physics Lab.

 Copyright (C) 1986, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/jhuapl/isarray.pro)

ISMEUV

 NAME:
       ISMEUV
 PURPOSE:
       Compute the continuum interstellar EUV optical depth 

 EXPLANATION:
       The EUV optical depth is computed from the photoionization of
       hydrogen and helium.

 CALLING SEQUENCE:
       tau = ISMEUV( wave, Hcol, [ HeIcol, HeIIcol, /Fano ]

 INPUTS:
       wave - Vector of wavelength values (in Angstroms).   Useful range is
               40 - 912 A; at shorter wavelengths metal opacity should be
               considered, at longer wavelengths there is no photoionization.
       Hcol - Scalar specifying interstellar hydrogen column density in cm-2.
                 Typical values are 1E17 to 1E20.

 OUTPUT:
       tau - Vector giving resulting optical depth, same number of elements 
               as wave, non-negative values.   To obtain the attenuation of 
               an input spectrum, multiply by exp(-tau).

 OPTIONAL INPUTS:
       HeIcol - Scalar specifying neutral helium column density in cm-2.    
               Default is 0.1*Hcol (10% of hydrogen column)
       HeIIcol - Scalar specifying ionized helium column density in cm-2
               Default is 0 (no HeII)

 OPTIONAL INPUT KEYWORDS:
       /FANO - If this keyword is set and non-zero, then the 4 strongest 
               auto-ionizing resonances of He I are included.   The shape 
               of these resonances is given by a Fano profile - see Rumph, 
               Bowyer, & Vennes 1994, AJ, 107, 2108.  If these resonances are
               included then the input wavelength vector should have
               a fine (>~0.01 A) grid between 190 A and 210 A, since the
               resonances are very narrow.
 EXAMPLE:
       (1) One has a model EUV spectrum with wavelength, w (in Angstroms) and 
       flux,f .  Plot the model flux after attenuation by 1e18 cm-2 of HI, 
       with N(HeI)/N(HI) = N(HeII)/N(HI) = 0.05

       IDL> Hcol = 1e18
       IDL> plot, w, f*exp(-ismeuv(w, Hcol, .05*Hcol, .05*Hcol))

       (2)  Plot the cross-section of HeI from 180 A to 220 A for 1e18 cm-2
               of HeI, showing the auto-ionizing resonances.   This is 
               Figure 1 in Rumph et al. (1994)

       IDL> w = 180 + findgen(40000)*0.001        ;Need a fine wavelength grid
       IDL> plot, w, ismeuv(w, 0, 1e18, /Fano)          

 NOTES:
       (1) The more complete program  ismtau.pro at 
           http://hea-www.harvard.edu/PINTofALE/pro/ extends this work
           to shorter wavelengths and includes metal and molecular hydrogen
           opacities
       (2) This program only compute continuum opacities, and for example,
           the He ionization edges at 504 A  and 228 A are blurred by
           converging line absorptions (Dupuis et al. 1995. ApJ, 455, 574)
           
 HISTORY:
       Written,    W. Landsman                  October, 1994
       Adapted from ism.c at anonymous ftp site cea-ftp.cea.berkeley.edu
       by Pat Jelinsky, Todd Rumph & others.
       Converted to IDL V5.0   W. Landsman   September 1997
       Avoid underflow messages, support double prec.  W. Landsman October 2003

(See $IDLUTILS_DIR/goddard/pro/astro/ismeuv.pro)

IS_IEEE_BIG

 NAME:
	IS_IEEE_BIG
 PURPOSE:
	Determine if the current machine uses IEEE, big-endian numbers.
 EXPLANATION:
       (Big endian implies that byteorder XDR conversions are no-ops).
 CALLING SEQUENCE:
	flag = is_ieee_big()
 INPUT PARAMETERS:
       None
 RETURNS:
       1 if the machine appears to be IEEE-compliant, 0 if not.
 COMMON BLOCKS:
	None.
 SIDE EFFECTS:
	None
 RESTRICTIONS:
 PROCEDURE:
       The first byte of the two-byte representation of 1 is examined.
       If it is zero, then the data is stored in big-endian order.
 MODIFICATION HISTORY:
       Written 15-April-1996 by T. McGlynn for use in MRDFITS.
	13-jul-1997	jkf/acc	- added calls to check_math to avoid
				  underflow messages in V5.0 on Win32 (NT).
	Converted to IDL V5.0   W. Landsman   September 1997
       Follow RSI and just do a single test  W. Landsman   April 2003

(See $IDLUTILS_DIR/goddard/pro/misc/is_ieee_big.pro)

JDCNV

 NAME:
	JDCNV
 PURPOSE:
	Converts Gregorian dates to Julian days   

 EXPLANATION:
       For IDL versions V5.1 or greater, this procedure is superceded by
       JULDAY() function in the standard IDL distribution.   Note, however,
       that prior to V5.1 there wasa bug in JULDAY() that gave answers off
       by 0.5 days. 
        
 CALLING SEQUENCE:
	JDCNV, YR, MN, DAY, HR, JULIAN

 INPUTS:
 	YR = Year, integer scalar or vector
	MN = Month  integer (1-12) scalar or vector
	DAY = Day   integer 1-31) scalar or vector 
	HR  = Hours and fractions of hours of universal time (U.T.), scalar
              or vector
		
 OUTPUTS:
	JULIAN = Julian date (double precision) 

 EXAMPLE:
	To find the Julian Date at 1978 January 1, 0h (U.T.)

	IDL> JDCNV, 1978, 1, 1, 0., JULIAN

	will give JULIAN = 2443509.5
 NOTES:
	(1) JDCNV will accept vector arguments 
	(2) JULDATE is an alternate procedure to perform the same function

 REVISON HISTORY:
	Converted to IDL from Don Yeomans Comet Ephemeris Generator,
	B. Pfarr, STX, 6/15/88
	Converted to IDL V5.0   W. Landsman   September 1997
       Added checks on valid month, day ranges W. Landsman July 2008

(See $IDLUTILS_DIR/goddard/pro/astro/jdcnv.pro)

JPLEPHINTERP

 NAME:
   JPLEPHINTERP

 AUTHOR:
   Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
   craigm@lheamail.gsfc.nasa.gov
   UPDATED VERSIONs can be found on my WEB PAGE: 
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

 PURPOSE:
   Interpolate position and motion of planetary bodies (JPL Ephemeris)

 MAJOR TOPICS:
   Planetary Orbits, Interpolation

 CALLING SEQUENCE:
   JPLEPHINTERP, INFO, RAWDATA, T, X, Y, Z, [VX, VY, VZ, /EARTH, /SUN,
         OBJECTNAME=, CENTER=, TBASE=, POSUNITS=, VELUNITS= ]

 DESCRIPTION:

   JPLEPHINTERP interpolates the JPL DE200 or DE405 planetary
   ephemeris to find the positions and motions of planetary bodies.

   This routine is the second stage of a two-stage process to
   interpolate the JPL ephemeris.  In this first stage, the file is
   opened using JPLEPHREAD, and the relevant portions of the table
   are read and stored into the two variables INFO and RAWDATA.  In
   the second stage, the user actually interpolates the ephemeris for
   the desired bodies and to the desired ephemeris time using
   JPLEPHINTERP.

   The only independent variable which must be specified is T, the
   ephemeris time.  For low to moderate accuracy applications, T is
   simply the conventional calendar date, expressed in Julian days.
   See below for high precision applications.

   Upon output, the position components of the desired body are
   returned in parameters X, Y and Z, and if requested velocity
   components are returned in parameters VX, VY and VZ.  Coordinates
   are referred to the ephemeris's coordinate system: FK5 for
   JPL-DE200 and ICRS for JPL-DE405.  By default, the origin of
   coordinates is the solar system barycenter (SSB), unless another
   origin is selected using the CENTER keyword.

   Users must set the VELOCITY keyword to generate body velocities.
   By default they are not generated.

   Users can select the desired body by using either the EARTH or SUN
   keywords, or the OBJECTNAME keyword.

   By default, positions are returned in units of KM and velocities
   in units of KM/DAY.  However, the output units are selectable by
   setting the POSUNITS and VELUNITS keywords.

 High Precision Applications

   If the required precision is finer than a few hundred meters, the
   user must be aware that the formal definition of the ephemeris
   time is the coordinate time of a clock placed at the solar system
   barycenter (SSB).  If the user's time is measured by a clock
   positioned elsewhere, then various corrections must be applied.
   Usually, the most significant correction is that from the
   geocenter to the SSB (see Fairhead & Bretagnon 1990; Fukushima
   1995).  Not applying this correction creates an error with
   amplitude ~170 nano-light-seconds ( = 50 m) on the earth's
   position.  (see TDB2TDT)

   For high precision, the user should also specify the TBASE
   keyword.  TBASE should be considered a fixed epoch with respect to
   which T is measured; T should be small compared to TBASE.
   Internally, subtraction of large numbers occurs with TBASE first,
   so truncation error is minimized by specifying TBASE.

 Nutations and Librations

   This routine also provides information about earth nutations and
   lunar librations, which are stored in the JPL ephemeris tables.
   The POSUNITS and VELUNITS keywords do not affect these
   computations.

   Lunar librations in the form of three Euler angles are returned in
   X, Y, Z, in units of radians, and their time derivatives are
   returned in VX, VY, and VZ in units of radians per day.

   The earth nutation angles psi (nutation in longitude) and epsilon
   (nutation in obliquity) are returned in X and Y, in units of
   radians.  Their time derivatives are returned in VX and VY
   respectively.  The quantities returned in Z and VZ are undefined.

 Verification

   The precision routine has been verified using JPLEPHTEST, which is
   similar to the original JPL program EPHTEST.  For years 1950 to
   2050, JPLEPHINTERP reproduces the original JPL ephemeris to within
   1 centimeter.

 Custom Ephemerides

   It is possible to make custom ephemerides using JPLEPHMAKE, or to
   augmented an existing ephemeris with additional data.  In the
   former case JPLEPHINTERP should automatically choose the correct
   object from the table and interpolate it appropriately.

   For augmented ephemerides, the object can be specified by name,
   which works as expected, or by number, which has a special
   behavior.  For augmented files only, the new objects begin at
   number 100.


 PARAMETERS: 

   INFO - structure returned by JPLEPHREAD.  Users should not modify
          this structure.

   RAWDATA - raw data array returned by JPLEPHREAD.  Users should not
             modify this data array.

   T - ephemeris time(s) of interest, relative to TBASE (i.e. the
       actual interpolation time is (T+TBASE)).  May be a scalar or
       vector.

   X, Y, Z - upon return, the x-, y- and z-components of the body
             position are returned in these parameters.  For
             nutations and librations see above.

   VX, VY, VZ - upon return, the x-, y- and z-components of the body
                velocity are returned in these parameters, if the
                VELOCITY keyword is set.  For nutations and
                librations see above.


 KEYWORD PARAMETERS:

   EARTH, SUN - set one of these keywords if the desired body is the
                earth or the sun.  One of EARTH, SUN or OBJECTNAME
                must be specified.

   OBJECTNAME - a scalar string or integer, specifies the planetary
                body of interest.  May take any one of the following
                integer or string values.

                   1 - 'MERCURY'     9 - 'PLUTO'
                   2 - 'VENUS'      10 - 'MOON'  (earth's moon)
                   3 - 'EARTH'      11 - 'SUN'
                   4 - 'MARS'       12 - 'SOLARBARY' or 'SSB' (solar system barycenter)
                   5 - 'JUPITER'    13 - 'EARTHBARY' or 'EMB' (earth-moon barycenter)
                   6 - 'SATURN'     14 - 'NUTATIONS' (see above)
                   7 - 'URANUS'     15 - 'LIBRATIONS' (see above)
                   8 - 'NEPTUNE' 

                For custom ephemerides, the user should specify the
                object name or number.

                For augmented ephemerides, the user should specify
                the name.  If the number is specified, then numbers
                1-15 have the above meanings, and new objects are
                numbered starting at 100.

   CENTER - a scalar string or integer, specifies the origin of
            coordinates.  See OBJECTNAME for allowed values.
            Default: 12 (Solar system barycenter)

   VELOCITY - if set, body velocities are generated and returned in
              VX, VY and VZ.
              Default: unset (no velocities)

   POSUNITS - a scalar string specifying the desired units for X, Y,
              and Z.  Allowed values:
                 'KM' - kilometers  (default)
                 'CM' - centimeters
                 'AU' - astronomical units
                 'LT-S' - light seconds
               If angles are requested, this keyword is ignored and
               the units are always 'RADIANS'.

   VELUNITS - a scalar string specifying the desired units for VX, VY
              and VZ.  Allowed values:
                 'KM/DAY' - kilometers per day  (default)
                 'KM/S' - kilometers per second
                 'CM/S' - centimeters per second
                 'LT-S/S' - light seconds per second
                 'AU/DAY' - astronomical units per day

   TBASE - a scalar or vector, specifies a fixed epoch against wich T
           is measured.  The ephemeris time will be (T+TBASE).  Use
           this keyword for maximum precision.


 EXAMPLE:

   Find position of earth at ephemeris time 2451544.5 JD.  Units are
   in Astronomical Units.

   JPLEPHREAD, 'JPLEPH.200', pinfo, pdata, [2451544D, 2451545D]

   JPLEPHINTERP, pinfo, pdata, 2451544.5D, xearth, yearth, zearth, $
                 /EARTH, posunits='AU'
     

 REFERENCES:

   AXBARY, Arnold Rots.
      ftp://heasarc.gsfc.nasa.gov/xte/calib_data/clock/bary/

   HORIZONS, JPL Web-based ephermis calculator (Ephemeris DE406)
      http://ssd.jpl.nasa.gov/horizons.html
   
   Fairhead, L. & Bretagnon, P. 1990, A&A, 229, 240

   Fukushima, T. 1995, A&A, 294, 895

   Standish, E.M. 1982, "Orientation of the JPL Ephemerides,
      DE200/LE200, to the Dynamical Equinox of J2000", Astronomy &
      Astrophysics, vol. 114, pp. 297-302.

   Standish, E.M.: 1990, "The Observational Basis for JPL's DE200,
      the planetary ephemeris of the Astronomical Almanac", Astronomy
      & Astrophysics, vol. 233, pp. 252-271.    

 SEE ALSO
   JPLEPHREAD, JPLEPHINTERP, JPLEPHTEST, TDB2TDT, JPLEPHMAKE
   
 MODIFICATION HISTORY:
   Written and Documented, CM, Jun 2001
   Corrected bug in name conversion of NUTATIONS and LIBRATIONS, 18
     Oct 2001, CM
   Added code to handle custom-built ephemerides, 04 Mar 2002, CM
   Fix bug in evaluation of velocity (only appears in highest order
     polynomial term); JPLEPHTEST verification tests still pass;
     change is of order < 0.5 cm in position, 22 Nov 2004, CM
   Perform more validity checking on inputs; and more informative
     outputs, 09 Oct 2008, CM
   Allow SSB and EMB as shortcuts for solar system and earth-moon
     bary center, 15 Oct 2008, CM
   TBASE now allowed to be a vector or scalar, 01 Jan 2009, CM
   VELFAC keyword gives scale factor between POSUNITS and VELUNITS, 
     12 Jan 2009, CM

  $Id: jplephinterp.pro,v 1.18 2009/01/13 04:53:26 craigm Exp $

(See $IDLUTILS_DIR/goddard/pro/astro/jplephinterp.pro)

JPLEPHREAD

 NAME:
   JPLEPHREAD

 AUTHOR:
   Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
   craigm@lheamail.gsfc.nasa.gov
   UPDATED VERSIONs can be found on my WEB PAGE: 
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

 PURPOSE:
   Open and read JPL DE200 or DE405 Ephemeride FITS File

 MAJOR TOPICS:
   Planetary Orbits, Interpolation

 CALLING SEQUENCE:
   JPLEPHREAD, FILENAME, INFO, RAWDATA, JDLIMITS, STATUS=, ERRMSG=

 DESCRIPTION:

   JPLEPHREAD opens and reads the JPL DE200 or DE405 planetary
   ephemerides, as available in FITS format.  The user must have the
   IDL Astronomy Library installed to use this routine.

   This routine is the initialization stage of a two-stage process to
   interpolate the JPL ephemeris.  In this first stage, the file is
   opened, and the relevant portions of the table are read and stored
   into the two variables INFO and RAWDATA.  In the second stage, the
   user actually interpolates the ephemeris for the desired bodies
   and to the desired ephemeris time using JPLEPHINTERP.

   Users must decide ahead of time the approximate dates of interest,
   and pass this range in the JDLIMITS parameter.  Any date covered
   by the ephemeris is valid.

   JPLEPHREAD is able to read files of the following format:
     DE200 - Chebyshev - FITS format - Note 1
     DE405 - Chebyshev - FITS format - Note 1
     DE200 - Taylor    - FITS format - Note 2

   Note 1 - Chebyshev formatted FITS files are available in the
            AXBARY package by Arnold Rots, found here:
              ftp://heasarc.gsfc.nasa.gov/xte/calib_data/clock/bary/
            or at the Markwardt FTP site:
              ftp://cow.physics.wisc.edu/pub/craigm/bary/

   Note 2 - Taylor-series based ephemerides have been available for
            years in the FTOOLS / LHEASOFT package produced by NASA's
            Goddard Space Flight Center.  The original file is
            de200_new.fits, which covers the years 1959-2000,
            inclusive.  A newer file is named
            de200_1950-2050_v2.fits, and covers the years 1959-2050.
            See Markwardt FTP site for these files.

 PARAMETERS: 

   FILENAME - name of ephemeris file (scalar string).

   INFO - upon completion, information about the ephemeris data is
          returned in this parameter in the form of a structure.
          Users must not modify INFO, although several fields are
          useful and may be accessed read-only:
              TSTART/TSTOP (start and stop time of data in Julian
                            days);
              C (speed of light in km/s);
              DENUM (development ephemeris number [200 or 405])
              AU (1 astronomical unit, in units of light-seconds)

   RAWDATA - upon completion, raw ephemeris data is returned in this
             parameter.  Users are not meant to access this data
             directly, but rather to pass it to JPLEPHINTERP.

   JDLIMITS - a two-element vector (optional), describing the desired
              time range of interest.  The vector should have the
              form [TSTART, TSTOP], where TSTART and TSTOP are the
              beginning and ending times of the range, expressed in
              Julian days.
              Default: entire table is read (note, this can be
              several megabytes)


 KEYWORD PARAMETERS:

   STATUS - upon completion, a value of 1 indicates success, and 0
            indicates failure.

   ERRMSG - upon completion, an error message is returned in this
            keyword.  If there were no errors, then the returned
            value is the empty string, ''.


 EXAMPLE:

   Find position of earth at ephemeris time 2451544.5 JD.  Units are
   in Astronomical Units.

   JPLEPHREAD, 'JPLEPH.200', pinfo, pdata, [2451544D, 2451545D]

   JPLEPHINTERP, pinfo, pdata, 2451544.5D, xearth, yearth, zearth, $
                 /EARTH, posunits='AU'
     

 REFERENCES:

   AXBARY, Arnold Rots.
      ftp://heasarc.gsfc.nasa.gov/xte/calib_data/clock/bary/

   HORIZONS, JPL Web-based ephermis calculator (Ephemeris DE406)
      http://ssd.jpl.nasa.gov/horizons.html
   
   JPL Export Ephemeris FTP Site
      ftp://ssd.jpl.nasa.gov/pub/eph/planets/
      (ephemeris files are available here, however, they must be
      converted to FITS format using the "bin2eph" utility found in
      AXBARY)

   JPL Export Ephemeris CD-ROM - Ordering Information
      http://www.willbell.com/software/jpl.htm

   Standish, E.M. 1982, "Orientation of the JPL Ephemerides,
      DE200/LE200, to the Dynamical Equinox of J2000", Astronomy &
      Astrophysics, vol. 114, pp. 297-302.

   Standish, E.M.: 1990, "The Observational Basis for JPL's DE200,
      the planetary ephemeris of the Astronomical Almanac", Astronomy
      & Astrophysics, vol. 233, pp. 252-271.    

 SEE ALSO
   JPLEPHREAD, JPLEPHINTERP, JPLEPHTEST
 PROCEDURES USED:
     FXBCLOSE, FXBOPEN, FXPAR(), 
   
 MODIFICATION HISTORY:
   Written and Documented, CM, Jun 2001
   Use GETTOK() instead of STR_SEP()  W. Landsman  July 2002

  $Id: jplephread.pro,v 1.6 2001/07/01 03:32:02 craigm Exp $

(See $IDLUTILS_DIR/goddard/pro/astro/jplephread.pro)

JPLEPHTEST

 NAME:
   JPLEPHTEST

 AUTHOR:
   Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
   craigm@lheamail.gsfc.nasa.gov
   UPDATED VERSIONs can be found on my WEB PAGE: 
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

 PURPOSE:
   Test JPLEPHTEST with JPL test data set

 MAJOR TOPICS:
   Planetary Orbits, Interpolation

 CALLING SEQUENCE:
   JPLEPHTEST, EPHFILE, TESTFILE

 DESCRIPTION:

   JPLEPHTEST tests the JPLEPHINTERP procedure for precision.  In
   order to function, you must have a JPL ephemeris test data set.
   The test data set testpo.405 is available in 
   ftp://idlastro.gsfc.nasa.gov/pub/data

   The procedure opens and reads the test set, which contains
   precomputed data.  Every tenth value is printed on the screen.
   Any deviations that exceed 1.5d-13 AU = 1.5 cm are reported.

   The columns are labelled according to the input file, except for
   the final column, which is the deviation between the input file
   and the computed value.


 PARAMETERS: 

   EPHFILE - a scalar string, specifies the name of the ephemeris
             file, in FITS format.    JPLEPHTEST will look in the directory
             $ASTRO_DATA for the file if it is not in the current directory.

   TESTFILE - a scalar string, specifies JPL test data set to compare
              against.   JPLEPHTEST will look in the directory
             $ASTRO_DATA for the file if it is not in the current directory.


 EXAMPLE:

   Test JPL DE200 and DE405 ephemerides.  Assumes files are in the
   current directory.

   JPLEPHTEST, 'JPLEPH.200', 'testpo.200'
   JPLEPHTEST, 'JPLEPH.405', 'testpo.405'
     

 REFERENCES:

   JPL Export Ephemeris FTP Site
      ftp://ssd.jpl.nasa.gov/pub/eph/planets/
      (see test-data/ for test data sets)
   
   HORIZONS, JPL Web-based ephermis calculator (Ephemeris DE406)
      http://ssd.jpl.nasa.gov/horizons.html


 SEE ALSO
   JPLEPHREAD, JPLEPHINTERP, JPLEPHTEST
   
 MODIFICATION HISTORY:
   Written and Documented, CM, Jun 2001
   Removed TRANSREAD, improved output, improved docs, CM, 9 Jul 2001

  $Id: jplephtest.pro,v 1.4 2001/07/20 13:29:53 craigm Exp $

(See $IDLUTILS_DIR/goddard/pro/astro/jplephtest.pro)

JPRECESS

 NAME:
      JPRECESS
 PURPOSE:
      Precess astronomical coordinates from B1950 to J2000
 EXPLANATION:
      Calculate the mean place of a star at J2000.0 on the FK5 system from the
      mean place at B1950.0 on the FK4 system.

      Use BPRECESS for the reverse direction J2000 ==> B1950
 CALLING SEQUENCE:
      jprecess, ra, dec, ra_2000, dec_2000, [ MU_RADEC = , PARALLAX = 
               RAD_VEL =, EPOCH =   ]

 INPUTS:
      RA,DEC - input B1950 right ascension and declination in *degrees*.
               Scalar or vector

 OUTPUTS:
      RA_2000, DEC_2000 - the corresponding J2000 right ascension and 
               declination in *degrees*.   Same number of elements as RA,DEC
               but always double precision. 

 OPTIONAL INPUT-OUTPUT KEYWORDS
      MU_RADEC - 2xN element double precision vector containing the proper 
                  motion in seconds of arc per tropical *century* in right 
                  ascension and declination.
      PARALLAX - N_element vector giving stellar parallax (seconds of arc)
      RAD_VEL  - N_element vector giving radial velocity in km/s

       The values of MU_RADEC, PARALLAX, and RADVEL will all be modified
       upon output to contain the values of these quantities in the
       J2000 system.    Values will also be converted to double precision.  
       The parallax and radial velocity will have a very minor influence on 
       the J2000 position.

       EPOCH - scalar giving epoch of original observations, default 1950.0d
           This keyword value is only used if the MU_RADEC keyword is not set.
  NOTES:
       The algorithm is taken from the Explanatory Supplement to the 
       Astronomical Almanac 1992, page 184.
       Also see Aoki et al (1983), A&A, 128,263

       JPRECESS distinguishes between the following two cases:
       (1) The proper motion is known and non-zero
       (2) the proper motion is unknown or known to be exactly zero (i.e.
               extragalactic radio sources).   In this case, the algorithm
               in Appendix 2 of Aoki et al. (1983) is used to ensure that
               the output proper motion is  exactly zero.    Better precision
               can be achieved in this case by inputting the EPOCH of the
               original observations.

       The error in using the IDL procedure PRECESS for converting between
       B1950 and J2000 can be up to 12", mainly in right ascension.   If
       better accuracy than this is needed then JPRECESS should be used.

 EXAMPLE:
       The SAO catalogue gives the B1950 position and proper motion for the 
       star HD 119288.   Find the J2000 position. 

          RA(1950) = 13h 39m 44.526s      Dec(1950) = 8d 38' 28.63''  
          Mu(RA) = -.0259 s/yr      Mu(Dec) = -.093 ''/yr

       IDL> mu_radec = 100D* [ -15D*.0259, -0.093 ]
       IDL> ra = ten(13,39,44.526)*15.D 
       IDL> dec = ten(8,38,28.63)
       IDL> jprecess, ra, dec, ra2000, dec2000, mu_radec = mu_radec
       IDL> print, adstring(ra2000, dec2000,2)
               ===> 13h 42m 12.740s    +08d 23' 17.69"

 RESTRICTIONS:
      "When transferring individual observations, as opposed to catalog mean
       place, the safest method is to tranform the observations back to the
       epoch of the observation, on the FK4 system (or in the system that was
       used to to produce the observed mean place), convert to the FK5 system,
       and transform to the the epoch and equinox of J2000.0" -- from the
       Explanatory Supplement (1992), p. 180

 REVISION HISTORY:
       Written,    W. Landsman                September, 1992
       Corrected a couple of typos in M matrix   October, 1992
       Vectorized, W. Landsman                   February, 1994
       Implement Appendix 2 of Aoki et al. (1983) for case where proper
       motion unknown or exactly zero     W. Landsman    November, 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Fixed typo in updating proper motion   W. Landsman   April 1999
       Make sure proper motion is floating point  W. Landsman December 2000
       Use V6.0 notation  W. Landsman Mar 2011

(See $IDLUTILS_DIR/goddard/pro/astro/jprecess.pro)

JULDATE

 NAME:
     JULDATE
 PURPOSE:                                   
     Convert from calendar to Reduced Julian Date

 EXPLANATION:
     Julian Day Number is a count of days elapsed since Greenwich mean noon 
     on 1 January 4713 B.C.  The Julian Date is the Julian day number
     followed by the fraction of the day elapsed since the preceding noon. 

     This procedure duplicates the functionality of the JULDAY() function in
     in the standard IDL distribution, but also allows interactive input and
     gives output as Reduced Julian date (=JD - 2400000.)  
     (Also note that prior to V5.1 there was a bug in JULDAY() that gave 
     answers offset by 0.5 days.)

 CALLING SEQUENCE:
     JULDATE, /PROMPT           ;Prompt for calendar Date, print Julian Date
               or
     JULDATE, date, jd      

 INPUT:
     DATE -  3 to 6-element vector containing year,month (1-12),day, and 
              optionally hour, minute, and second all specified as numbers
              (Universal Time).   Year should be supplied with all digits.
              Years B.C should be entered as negative numbers (and note that
              Year 0 did not exist).  If Hour, minute or seconds are not 
              supplied, they will default to 0. 

  OUTPUT:
       JD - Reduced Julian date, double precision scalar.  To convert to
               Julian Date, add 2400000.   JULDATE will print the value of
               JD at the terminal if less than 2 parameters are supplied, or 
               if the /PROMPT keyword is set
      
  OPTIONAL INPUT KEYWORD:
       /PROMPT - If this keyword is set and non-zero, then JULDATE will prompt
               for the calendar date at the terminal.

  RESTRICTIONS:
       The procedure HELIO_JD can be used after JULDATE, if a heliocentric
       Julian date is required.

  EXAMPLE:
       A date of 25-DEC-2006 06:25 UT may be expressed as either

       IDL> juldate, [2006, 12, 25, 6, 25], jd       
       IDL> juldate, [2006, 12, 25.2673611d], jd 

       In either case, one should obtain a Reduced Julian date of 
       JD = 54094.7673611

  PROCEDURE USED:
       GETOPT()
  REVISION HISTORY
       Adapted from IUE RDAF (S. Parsons)                      8-31-87
       Algorithm from Sky and Telescope April 1981   
       Added /PROMPT keyword, W. Landsman    September 1992
       Converted to IDL V5.0   W. Landsman   September 1997
       Make negative years correspond to B.C. (no year 0), work for year 1582
       Disallow 2 digit years.    W. Landsman    March 2000

(See $IDLUTILS_DIR/goddard/pro/astro/juldate.pro)

KSONE

 NAME:
       KSONE
 PURPOSE:
       Compute the one-sided Kolmogorov-Smirnov statistic
 EXPLANATION:
       Returns the Kolmogorov-Smirnov statistic and associated probability for 
       for an array of data values and a user-supplied cumulative distribution
       function (CDF) of a single variable.   Algorithm from the procedure of
       the same name in "Numerical Recipes" by Press et al. 2nd edition (1992)

 CALLING SEQUENCE:
       ksone, data, func_name, D, prob, [ /PLOT ]

 INPUT PARAMETERS:
       data -  vector of data values, must contain at least 4 elements for the
               K-S statistic to be meaningful 
       func_name - scalar string giving the name of the cumulative distribution
               function.    The function must be defined to accept the data
               vector as its only input (see example), though keywords may be
               passed via the _EXTRA facility.

 OUTPUT PARAMETERS:
       D - floating scalar giving the Kolmogorov-Smirnov statistic.   It 
               specified the maximum deviation between the cumulative 
               distribution of the data and the supplied function 
       prob - floating scalar between 0 and 1 giving the significance level of
               the K-S statistic.   Small values of PROB show that the 
               cumulative distribution function of DATA is significantly 
               different from FUNC_NAME.

 OPTIONAL INPUT KEYWORD:
       /PLOT - If this keyword is set and non-zero, then KSONE will display a
               plot of the CDF of the data with the supplied function 
               superposed.   The data value where the K-S statistic is 
               computed (i.e. at the maximum difference between the data CDF 
               and the function) is indicated by a vertical line.
               KSONE accepts the _EXTRA keyword, so that most plot keywords
               (e.g. TITLE, XTITLE, XSTYLE) can also be passed to KSONE.
       /WINDOW - If set, the plot to a resizeable graphics window
 EXAMPLE:
       Determine if a vector created by the RANDOMN function is really 
       consistent with a Gaussian distribution with unit variance.
       The CDF of a Gaussian is the error function except that a factor
       of 2 is included in the error function.   So we must create a special
       function:

       function gauss_cdf, x
       return, errorf( x/sqrt(2) )
       end

       IDL> data = randomn(seed, 50)          ;create data array to be tested
       IDL> ksone, abs(data), 'gauss_cdf', D, prob, /PLOT     ;Use K-S test
      
       A small value of PROB indicates that the cumulative distribution of 
        DATA is significantly different from a Gaussian

 NOTES:
       The code for PROB_KS is from the 2nd (1992) edition of Numerical 
       Recipes which includes a more accurate computation of the K-S 
       significance for small values of N than the first edition.

       Since _EXTRA is used to pass extra parameters both to the user-supplied
       function, and to the cgPLOT command, the user-supplied function should
       not accept "cgPLOT" keyword names (e.g. XTITLE).

 PROCEDURE CALLS
       procedure PROB_KS - computes significance of K-S distribution
       TAG_EXIST() 

 REVISION HISTORY:
       Written     W. Landsman                   August, 1992
       Accept _EXTRA keywords   W. Landsman      September, 1995          
       Fixed possible bug in plot display showing position maximum difference
       in histogram   M. Fardal/ W. Landsman      March, 1997
       Documentation updates   W. Landsman   June 2003
       Pass _EXTRA to func_name  M. Fitzgerald    April, 2005
       Work for functions that do not accept keywords W. Landsman July 2009
       Use Coyote graphics for plotting           Feb 2011

(See $IDLUTILS_DIR/goddard/pro/math/ksone.pro)

KSTWO

 NAME:
       KSTWO
 PURPOSE:
       Return the two-sided Kolmogorov-Smirnov statistic
 EXPLANATION:
       Returns the Kolmogorov-Smirnov statistic and associated probability 
       that two arrays of data values are drawn from the same distribution
       Algorithm taken from procedure of the same name in "Numerical
       Recipes" by Press et al., 2nd edition (1992), Chapter 14

 CALLING SEQUENCE:
       kstwo, data1, data2, D, prob

 INPUT PARAMATERS:
       data1 -  vector of data values, at least 4 data values must be included
               for the K-S statistic to be meaningful
       data2 -  second set of data values, does not need to have the same 
               number of elements as data1

 OUTPUT PARAMETERS:
       D - floating scalar giving the Kolmogorov-Smirnov statistic.   It
               specifies the maximum deviation between the cumulative 
               distribution of the data and the supplied function 
       prob - floating scalar between 0 and 1 giving the significance level of
               the K-S statistic.   Small values of PROB show that the 
               cumulative distribution function of DATA1 is significantly 
               different from DATA2

 EXAMPLE:
       Test whether two vectors created by the RANDOMN function likely came
       from the same distribution

       IDL> data1 = randomn(seed,40)        ;Create data vectors to be 
       IDL> data2 = randomn(seed,70)        ;compared
       IDL> kstwo, data1, data2, D, prob   & print,D,prob

 PROCEDURE CALLS
       procedure PROB_KS - computes significance of K-S distribution

 REVISION HISTORY:
       Written     W. Landsman                August, 1992
       FP computation of N_eff      H. Ebeling/W. Landsman  March 1996
       Fix for arrays containing equal values J. Ballet/W. Landsman Oct. 2001
       Fix index when maximum difference is at array end Renbin Yan  Dec 2008
       Handle large number when computing N_err  D. Schnitzeler/WL  Sep 2010

(See $IDLUTILS_DIR/goddard/pro/math/kstwo.pro)

KUIPERONE

 NAME:
       KUIPERONE
 PURPOSE:
       Compute the one-sided Kuiper statistic (invariant Kolmogorov-Smirnov)
 EXPLANATION:
       Returns the Kuiper statistic and associated probability
       for an array of data values and a user-supplied cumulative distribution
       function (CDF) of a single variable.   Algorithm adapted from KSONE
       in "Numerical Recipes" by Press et al. 2nd edition (1992)

       Kuiper's test is especially useful for data defined on a circle or 
       to search for periodicity (see Paltani 2004, A&A, 420, 789). 
 CALLING SEQUENCE:
       kuiperone, data, func_name, D, prob, [ /PLOT ]

 INPUT PARAMETERS:
       data -  vector of data values, must contain at least 4 elements for the
               Kuiper statistic to be meaningful
       func_name - scalar string giving the name of the cumulative distribution
               function.    The function must be defined to accept the data
               vector as its only input (see example).

 OUTPUT PARAMETERS:
       D - floating scalar giving the Kuiper statistic.   It
               specifies the sum of positive and negative deviations between the
               cumulative distribution of the data and the supplied function
       prob - floating scalar between 0 and 1 giving the significance level of
               the Kuiper statistic.   Small values of PROB show that the
               cumulative distribution function of DATA is significantly
               different from FUNC_NAME.

 OPTIONAL INPUT KEYWORD:
       /PLOT - If this keyword is set and non-zero, then KUIPERONE will display a
               plot of the CDF of the data with the supplied function
               superposed.   The data values where the Kuiper statistic is
               computed (i.e. at the maximum difference between the data CDF
               and the function) are indicated by vertical dashed lines.
               KUIPERONE accepts the _EXTRA keyword, so that most plot keywords
               (e.g. TITLE, XTITLE, XSTYLE) can also be passed to KUIPERONE.

 EXAMPLE:
       Determine if a vector created by the RANDOMN function is really
       consistent with a Gaussian distribution.
       The CDF of a Gaussian is the error function except that a factor
       of 2 is included in the error function.   So we must create a special
       function:

       function gauss_cdf, x
       return, errorf( x/sqrt(2) )
       end

       IDL> data = randomn(seed, 50)          ;create data array to be tested
       IDL> kuiperone, data, 'gauss_pdf', D, prob, /PLOT     ;Use Kuiper test

       A small value of PROB indicates that the cumulative distribution of
       DATA is significantly different from a Gaussian

 NOTES:
       Note that the 2nd (1992) edition of Numerical Recipes includes
       a more accurate computation of the K-S significance for small
       values of N.

 PROCEDURE CALLS
       procedure PROB_KUIPER - computes significance of Kuiper distribution

 REVISION HISTORY:
       Written     W. Landsman                   August, 1992
       Accept _EXTRA keywords   W. Landsman      September, 1995
       Fixed possible bug in plot display showing position maximum difference
       in histogram   M. Fardal/ W. Landsman      March, 1997
       Adapted from KSONE      J. Ballet     July 2003
       Use Coyote graphics   W. Landsman     Feb 2011

(See $IDLUTILS_DIR/goddard/pro/math/kuiperone.pro)

KUIPERTWO

 NAME:
       KUIPERTWO
 PURPOSE:
       Compute the two-sided Kuiper statistic (invariant Kolmogorov-Smirnov)
 EXPLANATION:
       Returns the Kuiper statistic and associated probability 
       that two arrays of data values are drawn from the same distribution
       Algorithm adapted from KSTWO in "Numerical
       Recipes" by Press et al., 2nd edition (1992), Chapter 14

 CALLING SEQUENCE:
       kuipertwo, data1, data2, D, prob, [ /PLOT ]

 INPUT PARAMETERS:
       data1 -  vector of data values, at least 4 data values must be included
               for the Kuiper statistic to be meaningful
       data2 -  second set of data values, does not need to have the same 
               number of elements as data1

 OUTPUT PARAMETERS:
       D - floating scalar giving the Kuiper statistic.   It
               specifies the sum of positive and negative deviations between
               the cumulative distributions of the two data sets
       prob - floating scalar between 0 and 1 giving the significance level of
               the Kuiper statistic.   Small values of PROB show that the 
               cumulative distribution function of DATA1 is significantly 
               different from DATA2

 OPTIONAL INPUT KEYWORD:
       /PLOT - If this keyword is set and non-zero, then KUIPERTWO will display
               a plot of the CDF of the two data sets.
               The data values where the Kuiper statistic is
               computed (i.e. at the maximum difference between the CDF of
               the two data sets) are indicated by vertical dashed lines.
               KUIPERTWO accepts the _EXTRA keyword, so that most plot keywords
               (e.g. TITLE, XTITLE, XSTYLE) can also be passed to KUIPERTWO.
       /WINDOW - If set the plot to a resizeable graphics window.
 EXAMPLE:
       Test whether two vectors created by the RANDOMN function likely came
       from the same distribution

       IDL> data1 = randomn(seed,40)        ;Create data vectors to be 
       IDL> data2 = randomn(seed,70)        ;compared
       IDL> kuipertwo, data1, data2, D, prob   & print,D,prob

 PROCEDURE CALLS
       procedure PROB_KUIPER - computes significance of Kuiper distribution

 REVISION HISTORY:
       Written     W. Landsman                August, 1992
       FP computation of N_eff      H. Ebeling/W. Landsman  March 1996
       Fix for arrays containing equal values J. Ballet/W. Landsman
       Oct. 2001
       Adapted from KSTWO, added PLOT keyword  J. Ballet     July 2004
       Use Coyote Graphics W. Landsman   Feb 2011

(See $IDLUTILS_DIR/goddard/pro/math/kuipertwo.pro)

LEGEND

 NAME:
       LEGEND
 PURPOSE:
       Create an annotation legend for a plot.
 EXPLANATION:
       NOTE: This procedure is *deprecated* because IDL 8.0 contains a LEGEND() 
       function written in IDL.   Both can be used provided that the one found 
       later in one's !PATH is  explicitly compiled in one's startup file.     
       However we strongly recommend the use of AL_LEGEND, which is identical
       in use to LEGEND.    legend.pro will eventually be removed from future 
       releases of the IDL Astron library.

       This procedure makes a legend for a plot.  The legend can contain
       a mixture of symbols, linestyles, Hershey characters (vectorfont),
       and filled polygons (usersym).  A test procedure, legendtest.pro,
       shows legend's capabilities.  Placement of the legend is controlled
       with keywords like /right, /top, and /center or by using a position
       keyword for exact placement (position=[x,y]) or via mouse (/position).
 CALLING SEQUENCE:
       LEGEND [,items][,keyword options]
 EXAMPLES:
       The call:
               legend,['Plus sign','Asterisk','Period'],psym=[1,2,3]
         produces:
               -----------------
               |               |
               |  + Plus sign  |
               |  * Asterisk   |
               |  . Period     |
               |               |
               -----------------
         Each symbol is drawn with a plots command, so they look OK.
         Other examples are given in optional output keywords.

       lines = indgen(6)                       ; for line styles
       items = 'linestyle '+strtrim(lines,2)   ; annotations
       legend,items,linestyle=lines            ; vertical legend---upper left
       items = ['Plus sign','Asterisk','Period']
       sym = [1,2,3]
       legend,items,psym=sym                   ; ditto except using symbols
       legend,items,psym=sym,/horizontal       ; horizontal format
       legend,items,psym=sym,box=0             ; sans border
       legend,items,psym=sym,delimiter='='     ; embed '=' betw psym & text
       legend,items,psym=sym,margin=2          ; 2-character margin
       legend,items,psym=sym,position=[x,y]    ; upper left in data coords
       legend,items,psym=sym,pos=[x,y],/norm   ; upper left in normal coords
       legend,items,psym=sym,pos=[x,y],/device ; upper left in device coords
       legend,items,psym=sym,/position         ; interactive position
       legend,items,psym=sym,/right            ; at upper right
       legend,items,psym=sym,/bottom           ; at lower left
       legend,items,psym=sym,/center           ; approximately near center
       legend,items,psym=sym,number=2          ; plot two symbols, not one
       legend,items,/fill,psym=[8,8,8],colors=[10,20,30]; 3 filled squares
 INPUTS:
       items = text for the items in the legend, a string array.
               For example, items = ['diamond','asterisk','square'].
               You can omit items if you don't want any text labels.
 OPTIONAL INPUT KEYWORDS:

       linestyle = array of linestyle numbers  If linestyle[i] < 0, then omit
               ith symbol or line to allow a multi-line entry.     If 
               linestyle = -99 then text will be left-justified.  
       psym = array of plot symbol numbers.  If psym[i] is negative, then a
               line connects pts for ith item.  If psym[i] = 8, then the
               procedure usersym is called with vertices define in the
               keyword usersym.   If psym[i] = 88, then use the previously
               defined user symbol.    If 11 <= psym[i] <= 46 then David
               Fanning's function SYMCAT() will be used for additional symbols.
               (http://www.idlcoyote.com/programs/symcat.pro).   Note that
               PSYM=10 (histogram plot mode) is not allowed since it 
               cannot be used with the PLOTS command.
       vectorfont = vector-drawn characters for the sym/line column, e.g.,
               ['!9B!3','!9C!3','!9D!3'] produces an open square, a checkmark,
               and a partial derivative, which might have accompanying items
               ['BOX','CHECK','PARTIAL DERIVATIVE'].
               There is no check that !p.font is set properly, e.g., -1 for
               X and 0 for PostScript.  This can produce an error, e.g., use
               !20 with PostScript and !p.font=0, but allows use of Hershey
               *AND* PostScript fonts together.
       N. B.: Choose any of linestyle, psym, and/or vectorfont.  If none is
               present, only the text is output.  If more than one
               is present, all need the same number of elements, and normal
               plot behaviour occurs.
               By default, if psym is positive, you get one point so there is
               no connecting line.  If vectorfont[i] = '',
               then plots is called to make a symbol or a line, but if
               vectorfont[i] is a non-null string, then xyouts is called.
       /help = flag to print header
       /horizontal = flag to make the legend horizontal
       /vertical = flag to make the legend vertical (D=vertical)
       box = flag to include/omit box around the legend (D=include)
		  outline_color = color of box outline (D = !P.color)
       bthick = thickness of the legend box (D = !P.thick)
       clear = flag to clear the box area before drawing the legend
       delimiter = embedded character(s) between symbol and text (D=none)
       colors = array of colors for plot symbols/lines (D=!P.color)
       font = scalar font graphics keyword (-1,0 or 1) for text
       textcolors = array of colors for text (D=!P.color)
       margin = margin around text measured in characters and lines
       spacing = line spacing (D=bit more than character height)
       linsize = Scale factor for line length (0-1), default = 1
                 Set to 0 to give a dot, 0.5 give half default line length   
       pspacing = psym spacing (D=3 characters) (when number of symbols is
             greater than 1)
       charsize = just like !p.charsize for plot labels
       charthick = just like !p.charthick for plot labels
       thick = array of line thickness numbers (D = !P.thick), if used, then 
               linestyle must also be specified
       position = data coordinates of the /top (D) /left (D) of the legend
       normal = use normal coordinates for position, not data
       device = use device coordinates for position, not data
       number = number of plot symbols to plot or length of line (D=1)
       usersym = 2-D array of vertices, cf. usersym in IDL manual. 
             (/USERSYM =square, default is to use existing USERSYM definition)
       /fill = flag to fill the usersym
       /left_legend = flag to place legend snug against left side of plot
                 window (D)
       /right_legend = flag to place legend snug against right side of plot
               window.    If /right,pos=[x,y], then x is position of RHS and
               text runs right-to-left.
       /top_legend = flag to place legend snug against top of plot window (D)
       /bottom = flag to place legend snug against bottom of plot window
               /top,pos=[x,y] and /bottom,pos=[x,y] produce same positions.

       If LINESTYLE, PSYM, VECTORFONT, THICK, COLORS, or TEXTCOLORS are
       supplied as scalars, then the scalar value is set for every line or
       symbol in the legend.
 Outputs:
       legend to current plot device
 OPTIONAL OUTPUT KEYWORDS:
       corners = 4-element array, like !p.position, of the normalized
         coords for the box (even if box=0): [llx,lly,urx,ury].
         Useful for multi-column or multi-line legends, for example,
         to make a 2-column legend, you might do the following:
           c1_items = ['diamond','asterisk','square']
           c1_psym = [4,2,6]
           c2_items = ['solid','dashed','dotted']
           c2_line = [0,2,1]
           legend,c1_items,psym=c1_psym,corners=c1,box=0
           legend,c2_items,line=c2_line,corners=c2,box=0,pos=[c1[2],c1[3]]
           c = [c1[0]<c2[0],c1[1]<c2[1],c1[2]>c2[2],c1[3]>c2[3]]
           plots,[c[0],c[0],c[2],c[2],c[0]],[c[1],c[3],c[3],c[1],c[1]],/norm
         Useful also to place the legend.  Here's an automatic way to place
         the legend in the lower right corner.  The difficulty is that the
         legend's width is unknown until it is plotted.  In this example,
         the legend is plotted twice: the first time in the upper left, the
         second time in the lower right.
           legend,['1','22','333','4444'],linestyle=indgen(4),corners=corners
                       ; BOGUS LEGEND---FIRST TIME TO REPORT CORNERS
           xydims = [corners[2]-corners[0],corners[3]-corners[1]]
                       ; SAVE WIDTH AND HEIGHT
           chdim=[!d.x_ch_size/float(!d.x_size),!d.y_ch_size/float(!d.y_size)]
                       ; DIMENSIONS OF ONE CHARACTER IN NORMALIZED COORDS
           pos = [!x.window[1]-chdim[0]-xydims[0] $
                       ,!y.window[0]+chdim[1]+xydims[1]]
                       ; CALCULATE POSITION FOR LOWER RIGHT
           plot,findgen(10)    ; SIMPLE PLOT; YOU DO WHATEVER YOU WANT HERE.
           legend,['1','22','333','4444'],linestyle=indgen(4),pos=pos
                       ; REDO THE LEGEND IN LOWER RIGHT CORNER
         You can modify the pos calculation to place the legend where you
         want.  For example to place it in the upper right:
           pos = [!x.window[1]-chdim[0]-xydims[0],!y.window[1]-xydims[1]]
 Common blocks:
       none
 Procedure:
       If keyword help is set, call doc_library to print header.
       See notes in the code.  Much of the code deals with placement of the
       legend.  The main problem with placement is not being
       able to sense the length of a string before it is output.  Some crude
       approximations are used for centering.
 Restrictions:
       Here are some things that aren't implemented.
       - An orientation keyword would allow lines at angles in the legend.
       - An array of usersyms would be nice---simple change.
       - An order option to interchange symbols and text might be nice.
       - Somebody might like double boxes, e.g., with box = 2.
       - Another feature might be a continuous bar with ticks and text.
       - There are no guards to avoid writing outside the plot area.
       - There is no provision for multi-line text, e.g., '1st line!c2nd line'
         Sensing !c would be easy, but !c isn't implemented for PostScript.
         A better way might be to simply output the 2nd line as another item
         but without any accompanying symbol or linestyle.  A flag to omit
         the symbol and linestyle is linestyle[i] = -1.
       - There is no ability to make a title line containing any of titles
         for the legend, for the symbols, or for the text.
 Side Effects:
 Modification history:
       write, 24-25 Aug 92, F K Knight (knight@ll.mit.edu)
       allow omission of items or omission of both psym and linestyle, add
         corners keyword to facilitate multi-column legends, improve place-
         ment of symbols and text, add guards for unequal size, 26 Aug 92, FKK
       add linestyle(i)=-1 to suppress a single symbol/line, 27 Aug 92, FKK
       add keyword vectorfont to allow characters in the sym/line column,
         28 Aug 92, FKK
       add /top, /bottom, /left, /right keywords for automatic placement at
         the four corners of the plot window.  The /right keyword forces
         right-to-left printing of menu. 18 Jun 93, FKK
       change default position to data coords and add normal, data, and
         device keywords, 17 Jan 94, FKK
       add /center keyword for positioning, but it is not precise because
         text string lengths cannot be known in advance, 17 Jan 94, FKK
       add interactive positioning with /position keyword, 17 Jan 94, FKK
       allow a legend with just text, no plotting symbols.  This helps in
         simply describing a plot or writing assumptions done, 4 Feb 94, FKK
       added thick, symsize, and clear keyword Feb 96, W. Landsman HSTX
               David Seed, HR Wallingford, d.seed@hrwallingford.co.uk
       allow scalar specification of keywords, Mar 96, W. Landsman HSTX
       added charthick keyword, June 96, W. Landsman HSTX
       Made keyword names  left,right,top,bottom,center longer,
                                 Aug 16, 2000, Kim Tolbert
       Added ability to have regular text lines in addition to plot legend 
       lines in legend.  If linestyle is -99 that item is left-justified.
       Previously, only option for no sym/line was linestyle=-1, but then text
       was lined up after sym/line column.    10 Oct 2000, Kim Tolbert
       Make default value of thick = !P.thick  W. Landsman  Jan. 2001
       Don't overwrite existing USERSYM definition  W. Landsman Mar. 2002
	     Added outline_color BT 24 MAY 2004
       Pass font keyword to xyouts commands.  M. Fitzgerald, Sep. 2005
       Default spacing, pspacing should be relative to charsize. M. Perrin, July 2007
       Don't modify position keyword  A. Kimball/ W. Landsman Jul 2007
       Small update to Jul 2007 for /NORMAL coords.  W. Landsman Aug 2007
       Use SYMCAT() plotting symbols for 11<=PSYM<=46   W. Landsman  Nov 2009
       Make a sharper box edge T. Robishaw/W.Landsman July 2010
       Added BTHICK keyword W. Landsman October 2010
       Added LINESIZ keyword W.L./V.Gonzalez   May 2011
       Use CHARSIZE instead of SIZE keyword in XYOUTS  W.L./S.Erard Jul 2011

(See $IDLUTILS_DIR/goddard/pro/plot/legend.pro)

LEGENDTEST

 NAME:
	LEGENDTEST
 PURPOSE:
	Demo program to show capabilities of  the legend procedure.
 CALLING SEQUENCE:
	legendtest
 INPUTS:
	none
 OPTIONAL INPUTS:
	none
 KEYWORDS:
	none
 OUTPUTS:
	legends of note
 COMMON BLOCKS:
	none
 SIDE EFFECTS:
	Sets !20 font to symbol if PostScript and !p.font=0.
 RESTRICTIONS:
	With the vectorfont test, you'll get different results for PostScript
	depending on the value of !p.font.
 MODIFICATION HISTORY:
	write, 27 Aug 92, F.K.Knight (knight@ll.mit.edu)
	add test of /left,/right,/top,/bottom keywords, 21 June 93, FKK
	update based on recent changes to legend, 7 Feb 94, FKK
       Fix ambiguous CHAR keyword  W. Landsman Sep 2007
       Use Coyote graphics routines  W. Landsman Jan 2011

(See $IDLUTILS_DIR/goddard/pro/plot/legendtest.pro)

LINEID_PLOT

 NAME:
	LINEID_PLOT
 PURPOSE:
	 Plot spectrum with specified line identifications annotated at the
	 top of the plot.

 CALLING SEQUENCE:
	lineid_plot, wave, flux, wline, text1, [ text2, 
			LCHARSIZE=, LCHARTHICK=, EXTEND =, ...plotting keywords]

 INPUTS:
	wave - wavelength vector for the plot
	flux - flux vector
	wline - wavelength vector of line identifications.  (only the lines 
		between	the plot limits will be used)
	text1 - string array of text to be used to annotate each line
	text2 - (OPTIONAL) second string array of text to be used for
		line annotation.  Since the text is written with
		proportional spaced characters, TEXT2 can be used if
		you want two sets of annotation to be alinged:

		eg:	Cr IV  1390.009
			Fe V   1390.049
			Ni IV  1390.184
			    instead of
			Cr IV 1390.009
			Fe V 1390.049
			Ni IV 1390.184

 OPTIONAL KEYWORD INPUTS:
	EXTEND - specifies that the annotated lines should have a dotted line 
		extended to the spectrum to indicate the line position.  
		EXTEND can be a scalar (applies to all lines) or a vector with
		a different value for each line.  The value of EXTEND gives 
		the line IDL plot line thickness for the dotted lines.
		If EXTEND is a vector each dotted line can have a different 
		thickness.  A value of 0 indicates that no dotted line is to 
		be drawn. (default = scalar 0)
	LCHARSIZE - the character size of the annotation for each line.
		If can be a vector so that different lines are annotated with 
		different size characters.  LCHARSIZE can be used to make 
		stronger lines have a larger annotation. (default = scalar 1.0).
	LCHARTHICK = the character thickness of the annotation for each line. 
		It can be a vector so that different lines are annotated with 
		characters of varying thickness.   LCHARTHICK can be used to 
		make stronger lines have a bolder annotation. 
		(default = !p.charthick)

	LINEID_PLOT uses the _EXTRA facility to allow the use of any cgPLOT
	keywords (e.g. AXISCOLOR, LINESTYLE, CHARSIZE) to be passed to the 
       plot.

 SIDE EFFECTS:
	Program uses SET_VIEWPORT to set the !P.POSITION parameter to allow
	room for the annotation.   This system variable can be reset to the 
	default value by setting !P.POSTION=0 or typing SET_VIEWPORT with no 
	parameters

 OPERATIONAL NOTES:
	Once the program has completed, You can use OPLOT to draw additional
	plots on the display. 

	If your annotated characters are not being rotated properly,
	try setting !P.FONT to a non zero value.
 EXAMPLE:
	Annotate some interstellar lines between 1240 and 1270 A.

	IDL> w = 1240+ indgen(300)*0.1    ;Make a wavelength vector
	IDL> f = randomn(seed,300)        ;Random flux vector
	IDL> id = ['N V','Si II','Si II','Si II']   ;Line IDs
	IDL> wl = [1242.80,1260.42,1264.74,1265.00] ;Line positions
	IDL> lineid_plot,w,f,wl,id,wl,/ext

	Note that LINEID_PLOT is smart enough not to overlap the annotation
	for the two closely spaced lines at 1264.74 and 1265.00	
 HISTORY:
	version 1  D. Lindler Jan, 1992
	Sept 27, 1993  DJL  fixed bug in /extend option
	Apr 19, 1994 DJL corrected bug in sorting of charthick (cthick)
	Sep 1996, W. Landsman,  added _EXTRA keyword, changed keyword names
		CHARTHICK==>LCHARTHICK, CHARSIZE==>LCHARSIZE
       Work with !P.MULTI   W. Landsman   December 2003
       Use Coyote graphics routines  W. Landsman February 2011

(See $IDLUTILS_DIR/goddard/pro/plot/lineid_plot.pro)

LINKEDLIST

 NAME:
   LINKEDLIST

 FILENAME:
   linkedlist__define.pro

 PURPOSE:
 
   The purpose of this program is to implement a list that
   is linked in both the forward and backward directions. There
   is no restriction as to what can be stored in a linked list
   node. The linked list is implemented as an object.

 AUTHOR:
 
   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:
 
   General programming.

 CALLING SEQUENCE:
 
   mylist = Obj_New('LINKEDLIST', item)

 OPTIONAL INPUTS:
 
   item: The first item added to the list. Items can be any
     valid IDL variable type.

 COMMON BLOCKS:
 
   Are you kidding?!

 RESTRICTIONS:
 
   Be sure to destroy the LINKEDLIST object when you are finished
   with it: Obj_Destroy, mylist

   Node index numbers start at 0 and go to n-1, where n is the
   number of items in the list.

 PUBLIC METHODS:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 PRO LINKEDLIST::ADD, item, index, $
     AFTER=after, $
     BEFORE=before, $
     ERROR=error, $
     NO_COPY=no_copy, $
     REPLACE=replace
     

   The ADD method adds a data item to the list.

   Parameters:

   item: The data item to be added to the list. Required.

   index: The location in the list where the data item is
     to be added. If neither the AFTER or BEFORE keyword is
     set, the item is added AFTER the item at the index location.
     If index is missing, the index points to the last item in
     the list. Optional.

   Keywords:

   AFTER: If this keyword is set, the item is added after the
     item at the current index.

   BEFORE: If this keyword is set, the item is added before the
     item at the current index.
     
   ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.
      
   NO_COPY: If set, the item is transferred to the internal pointer using
      a no copy method. This will cause the item variable to become undefined.
      
   REPLACE: If this keyword is set, the item will replace the current item at
      the index location.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 PRO LINKEDLIST::DELETE, index, ALL=all, DESTROY=destroy, ERROR=error   
      
   The DELETE method deletes an item from the list.

   Parameters:

   index: The location in the list where the data item is
     to be delete. If index is missing, the index points to
     the last item in the list. Optional.

   Keywords:

   ALL: If this keyword is set, all items in the list are deleted.

   DESTROY: If the item at the node is an object or pointer, the
     item will be destroyed before the node is deleted. This keyword
     is turned on (set to 1) by default. Set to 0 to prevent destruction.

    ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 FUNCTION LINKEDLIST::GET_COUNT

   The GET_COUNT method returns the number of items in the list.

   Return Value: The number of items stored in the linked list.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


 FUNCTION LINKEDLIST::GET_ITEM, index, $
    ALL=all, $                 ; This ASSUMES all items stored are the same type!!!
    Dereference=dereference, $ ; Obsolete. Ignored. Always returns item.
    ItemPtr=itemPtr, $         ; The pointer to the item, if needed. Output.
    NO_COPY=no_copy, $         ; Copy from location with NO_COPY.
    ERROR=errorMsg             ; The error message. Null string if no error.


   Parameters:

   index: The location in the list from which the data item is
     to be retrieved. If not present, the last item in the list
     is retrieved. Optional.

   Keywords:

   DEREFERENCE: This keyword obsolete and only provided for backward compatibility.

   ALL: Set this keyword to return an n-element array containing all the list
      items.  This requires that all list items be of the same type, and
      if they are arrays, they have 7 dimensions or fewer. If index is passed, 
      it is ignored.
     
   ITEMPTR: The pointer to the data item.
   
   NO_COPY: If this keyword is set, the item is transferred from the data
      pointer using a NO_COPY method. This will undefine the item at that
      indexed locaton.
      
    ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.

   Return Value: The data item at this index on the list.
     If ALL is set, then an array containing all the data items is returned.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 FUNCTION LINKEDLIST::GET_NODE, index, ERROR=error

   The GET_NODE method returns a pointer to the specified node
   from the list.

   Parameters:

   index: The location in the list from which the data node is
     to be retrieved. If not present, the last node in the list
     is retrieved. The node is a structure with three fields:
     Previous is a pointer to the previous node in the list.
     Next is a pointer to the next node in the list. A null pointer
     in the previous field indicates the first node on the list. A
     null pointer in the next field indicates the last node on the
     list. The item field is a pointer to the item stored in the
     node. Optional.

   ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.
      
   Return Value: A pointer to the specified node structure in
     the linked list.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 PRO LINKEDLIST::HELP, PRINT=print

 The HELP method performs a HELP command on each item
 in the linked list.

   Keywords:

    PRINT: If this keyword is set, the PRINT command is used
      instead of the HELP command on the items in the list.

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

 PRO LINKEDLIST::MOVE_NODE, nodeIndex, location, BEFORE=before, ERROR=error

   The MOVE_NODE method moves a list node from one location to another.

   Parameters:

   nodeIndex: The location in the list of the node you are moving.
     Required.

   location: The location (index) you are moving the node to. If
     location is missing, the location points to the node at the
     end of the list.

   Keywords:

    BEFORE: If this keyword is set, the node is added to the
      list before the location node. Otherwise, it is added after
      the location node.

    ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.
      
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 PRO LINKEDLIST::REPLACE_ITEM, newItem, index, ERROR=error

  Use this method to replace any item in the list with any other value.
  This allows the caller to change an item without stepping through the
  process of deleting an item then adding a new one.

  Parameters:
     index:  The location of the node you are replacing

     newItem:  Any value of any data type.

    ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.
      
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 FUNCTION LINKEDLIST::HAVE_ITEM, index, ERROR=error

  Use this method to check to see if an item exits at a particular location
  on the list. Returns a 1 if the item is there, otherwise a 0.

  Parameters:
     index:  The location of the node you are replacing
      
    ERROR: On return, if this is not a null string, an error occurred
      and this value is set equal to the error message.
      
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


 EXAMPLE:

   mylist = Obj_New("LINKEDLIST", 5)
   mylist->Add, 10
   mylist->Add, 7, 1, /Before
   mylist->Add, 12
   print, mylist->Get_Item(/All)
   mylist->Add, 'Bob', 2, /Replace
   mylist->Help
   mylist->Delete, 0
   mylist->Help, /Print

 MODIFICATION HISTORY:
   Written by: David Fanning, 25 August 98.
   25 August 99. Fixed several errors in various methods dealing with
       moving nodes from one place to another. DWF.
   13 June 2001. DWF. Added DEREFERENCE to the GET_ITEM method to
       return the item itself, instead of the pointer to the item.
   27 June 2001 Added REPLACE_ITEM method.  Ben Tupper.
   7 April 2003. Added DESTROY keyword to DELETE method so that objects
      and pointers could be cleaned up properly when they are deleted
      from the linked list. DWF.
   9 April 2003. Fixed a problem that occurs when deleting the last node. DWF.
   3 Feb 2004. Make sure loop index vars are long.  Jeff Guerber
   30 Jun 2004.  Added /ALL to GET_ITEM function.  Henry Throop, SWRI.
   23 Nov 2004.  Fixed GET_ITEM, /ALL to accomodate structures and empty
      lists.  Henry Throop.
   21 February 2011. A complete refurbishing to incorporate changes and to fix bugs
      I found in the SolarSoft version of this code. I've tried to make this compatible
      with the version distributed with SolarSoft to reduce problems caused by two versions
      of the software with the same name.
    9 December 2011. Fixed a problem with the ALL keyword on the Get_Item method. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/linkedlist__define.pro)

LINMIX_ERR

   NAME:
     LINMIX_ERR
   PURPOSE:
      Bayesian approach to linear regression with errors in both X and Y
   EXPLANATION:
     Perform linear regression of y on x when there are measurement
     errors in both variables. the regression assumes :

                 ETA = ALPHA + BETA * XI + EPSILON
                 X = XI + XERR
                 Y = ETA + YERR


 Here, (ALPHA, BETA) are the regression coefficients, EPSILON is the
 intrinsic random scatter about the regression, XERR is the
 measurement error in X, and YERR is the measurement error in
 Y. EPSILON is assumed to be normally-distributed with mean zero and
 variance SIGSQR. XERR and YERR are assumed to be
 normally-distributed with means equal to zero, variances XSIG^2 and
 YSIG^2, respectively, and covariance XYCOV. The distribution of XI
 is modelled as a mixture of normals, with group proportions PI,
 mean MU, and variance TAUSQR. Bayesian inference is employed, and
 a structure containing random draws from the posterior is
 returned. Convergence of the MCMC to the posterior is monitored
 using the potential scale reduction factor (RHAT, Gelman et
 al.2004). In general, when RHAT < 1.1 then approximate convergence
 is reached.

 Simple non-detections on y may also be included.

 CALLING SEQUENCE:

     LINMIX_ERR, X, Y, POST, XSIG=, YSIG=, XYCOV=, DELTA=, NGAUSS=, /SILENT, 
                /METRO, MINITER= , MAXITER= 


 INPUTS :

   X - THE OBSERVED INDEPENDENT VARIABLE. THIS SHOULD BE AN
       NX-ELEMENT VECTOR.
   Y - THE OBSERVED DEPENDENT VARIABLE. THIS SHOULD BE AN NX-ELEMENT
       VECTOR.

 OPTIONAL INPUTS :

   XSIG - THE 1-SIGMA MEASUREMENT ERRORS IN X, AN NX-ELEMENT VECTOR.
   YSIG - THE 1-SIGMA MEASUREMENT ERRORS IN Y, AN NX-ELEMENT VECTOR.
   XYCOV - THE COVARIANCE BETWEEN THE MEASUREMENT ERRORS IN X AND Y,
           AND NX-ELEMENT VECTOR.
   DELTA - AN NX-ELEMENT VECTOR INDICATING WHETHER A DATA POINT IS
           CENSORED OR NOT. IF DELTA[i] = 1, THEN THE SOURCE IS
           DETECTED, ELSE IF DELTA[i] = 0 THE SOURCE IS NOT DETECTED
           AND Y[i] SHOULD BE AN UPPER LIMIT ON Y[i]. NOTE THAT IF
           THERE ARE CENSORED DATA POINTS, THEN THE
           MAXIMUM-LIKELIHOOD ESTIMATE (THETA) IS NOT VALID. THE
           DEFAULT IS TO ASSUME ALL DATA POINTS ARE DETECTED, IE,
           DELTA = REPLICATE(1, NX).
   METRO - IF METRO = 1, THEN THE MARKOV CHAINS WILL BE CREATED USING
           THE METROPOLIS-HASTINGS ALGORITHM INSTEAD OF THE GIBBS
           SAMPLER. THIS CAN HELP THE CHAINS CONVERGE WHEN THE SAMPLE
           SIZE IS SMALL OR IF THE MEASUREMENT ERRORS DOMINATE THE
           SCATTER IN X AND Y.
   SILENT - SUPPRESS TEXT OUTPUT.
   MINITER - MINIMUM NUMBER OF ITERATIONS PERFORMED BY THE GIBBS
             SAMPLER OR METROPOLIS-HASTINGS ALGORITHM. IN GENERAL,
             MINITER = 5000 SHOULD BE SUFFICIENT FOR CONVERGENCE. THE
             DEFAULT IS MINITER = 5000. THE MCMC IS STOPPED AFTER 
             RHAT < 1.1 FOR ALL PARAMETERS OF INTEREST, AND THE
             NUMBER OF ITERATIONS PERFORMED IS GREATER THAN MINITER.
   MAXITER - THE MAXIMUM NUMBER OF ITERATIONS PERFORMED BY THE
             MCMC. THE DEFAULT IS 1D5. THE MCMC IS STOPPED
             AUTOMATICALLY AFTER MAXITER ITERATIONS.
   NGAUSS - THE NUMBER OF GAUSSIANS TO USE IN THE MIXTURE
            MODELLING. THE DEFAULT IS 3. IF NGAUSS = 1, THEN THE
            PRIOR ON (MU, TAUSQR) IS ASSUMED TO BE UNIFORM.

 OUTPUT :

    POST - A STRUCTURE CONTAINING THE RESULTS FROM THE MCMC. EACH
           ELEMENT OF POST IS A DRAW FROM THE POSTERIOR DISTRIBUTION
           FOR EACH OF THE PARAMETERS.

             ALPHA - THE CONSTANT IN THE REGRESSION.
             BETA - THE SLOPE OF THE REGRESSION.
             SIGSQR - THE VARIANCE OF THE INTRINSIC SCATTER.
             PI - THE GAUSSIAN WEIGHTS FOR THE MIXTURE MODEL.
             MU - THE GAUSSIAN MEANS FOR THE MIXTURE MODEL.
             TAUSQR - THE GAUSSIAN VARIANCES FOR THE MIXTURE MODEL.
             MU0 - THE HYPERPARAMETER GIVING THE MEAN VALUE OF THE
                   GAUSSIAN PRIOR ON MU. ONLY INCLUDED IF NGAUSS >
                   1.
             USQR - THE HYPERPARAMETER DESCRIBING FOR THE PRIOR
                    VARIANCE OF THE INDIVIDUAL GAUSSIAN CENTROIDS
                    ABOUT MU0. ONLY INCLUDED IF NGAUSS > 1.
             WSQR - THE HYPERPARAMETER DESCRIBING THE `TYPICAL' SCALE
                    FOR THE PRIOR ON (TAUSQR,USQR). ONLY INCLUDED IF
                    NGAUSS > 1.
             XIMEAN - THE MEAN OF THE DISTRIBUTION FOR THE
                      INDEPENDENT VARIABLE, XI.
             XISIG - THE STANDARD DEVIATION OF THE DISTRIBUTION FOR
                     THE INDEPENDENT VARIABLE, XI.
             CORR - THE LINEAR CORRELATION COEFFICIENT BETWEEN THE
                    DEPENDENT AND INDEPENDENT VARIABLES, XI AND ETA.

 CALLED ROUTINES :

    RANDOMCHI, MRANDOMN, RANDOMGAM, RANDOMDIR, MULTINOM

 REFERENCES :

   Carroll, R.J., Roeder, K., & Wasserman, L., 1999, Flexible
     Parametric Measurement Error Models, Biometrics, 55, 44

   Kelly, B.C., 2007, Some Aspects of Measurement Error in
     Linear Regression of Astronomical Data, The Astrophysical
     Journal, 665, 1489 (arXiv:0705.2774)

   Gelman, A., Carlin, J.B., Stern, H.S., & Rubin, D.B., 2004,
     Bayesian Data Analysis, Chapman & Hall/CRC

 REVISION HISTORY

     AUTHOR : BRANDON C. KELLY, STEWARD OBS., JULY 2006
   - MODIFIED PRIOR ON MU0 TO BE UNIFORM OVER [MIN(X),MAX(X)] AND
     PRIOR ON USQR TO BE UNIFORM OVER [0, 1.5 * VARIANCE(X)]. THIS
     TENDS TO GIVE BETTER RESULTS WITH FEWER GAUSSIANS. (B.KELLY, MAY
     2007)
   - FIXED BUG SO THE ITERATION COUNT RESET AFTER THE BURNIN STAGE
     WHEN SILENT = 1 (B. KELLY, JUNE 2009)
   - FIXED BUG WHEN UPDATING MU VIA THE METROPOLIS-HASTING
     UPDATE. PREVIOUS VERSIONS DID NO INDEX MUHAT, SO ONLY MUHAT[0]
     WAS USED IN THE PROPOSAL DISTRIBUTION. THANKS TO AMY BENDER FOR
     POINTING THIS OUT. (B. KELLY, DEC 2011)

(See $IDLUTILS_DIR/goddard/pro/math/linmix_err.pro)

LINTERP

 NAME:   
       LINTERP  
 PURPOSE: 
       Linearly interpolate tabulated 1-d data from one grid to a new one.
 EXPLANATION:
       The results of LINTERP are numerically equivalent to the RSI
       INTERPOL() function, but note the following:
         (1) LINTERP is a procedure rather than a function
         (2) INTERPOL() extrapolates beyond the end points whereas LINTERP
             truncates to the endpoints (or uses the MISSING keyword)
         (3) LINTERP (unlike INTERPOL) uses the intrinsic INTERPOLATE function
                 and thus may have a speed advantage
         (4) LINTERP always converts the new grid vector to floating point 
                (because INTERPOLATE does this) whereas INTERPOL() will 
                 keep double precision if supplied.

       Use QUADTERP for quadratic interpolation.

 CALLING SEQUENCE:
       LINTERP, Xtab, Ytab, Xint, Yint, [MISSING =, /NoInterp ]   

 INPUT PARAMETERS: 
       Xtab -  Vector containing the current independent variable grid.
               Must be monotonic increasing or decreasing
       Ytab -  Vector containing the current dependent variable values at 
               the XTAB grid points.
       Xint -  Scalar or vector containing the new independent variable grid 
               points for which interpolated value(s) of the dependent 
               variable are sought.    Note that -- due to a limitation of the
               intrinsic INTERPOLATE() function -- Xint is always converted to
               floating point internally.

 OUTPUT PARAMETERS:
       Yint  -  Scalar or vector with the interpolated value(s) of the 
               dependent variable at the XINT grid points.
               YINT is double precision if XTAB or YTAB are double,
               otherwise YINT is REAL*4

 OPTIONAL INPUT KEYWORD:
       MISSING - Scalar specifying YINT value(s) to be assigned, when Xint
               value(s) are outside of the range of Xtab.     Default is to
               truncate the out of range YINT value(s) to the nearest value 
               of YTAB.   See the help for the INTERPOLATE function.
       /NoINTERP - If supplied then LINTERP returns the YTAB value(s) 
               associated with the closest XTAB value(s)rather than 
               interpolating.

 EXAMPLE:
       To linearly interpolate from a spectrum wavelength-flux pair
       WAVE, FLUX to another wavelength grid defined as:
       WGRID = [1540., 1541., 1542., 1543., 1544, 1545.]
   
       IDL>  LINTERP, WAVE, FLUX, WGRID, FGRID  

       FGRID will be a 6 element vector containing the values of FLUX 
       linearly interpolated onto the WGRID wavelength scale

 PROCEDURE: 
       Uses TABINV to calculate the effective index of the values
       in Xint in the table Xtab.  The resulting index is used
       with the intrinsic INTERPOLATE function to find the corresponding 
       Yint value in Ytab.  Unless the MISSING keyword is supplied, out
       of range Yint values are truncated to the nearest value of Ytab.

 PROCEDURES CALLED:
       TABINV, ZPARCHECK
 MODIFICATION HISTORY:
       Adapted from the IUE RDAF,  W. Landsman      October, 1988
       Modified to use the new INTERPOLATE function        June, 1992
       Modified to always return REAL*4             October, 1992
       Added MISSING keyword                        August, 1993
       Converted to IDL V5.0   W. Landsman   September 1997
       Added NoInterp keyword  W. Landsman      July 1999
       Work for unsigned, 64 bit integers  W. Landsman  October 2001

(See $IDLUTILS_DIR/goddard/pro/math/linterp.pro)

LIST_WITH_PATH

 NAME: 
	LIST_WITH_PATH
 PURPOSE: 
	Search for files in a specified directory path.
 EXPLANATION:
	Lists files in a set of default paths, similar to using FILE_SEARCH,
	except that a list of paths to be searched can be given.

 CALLING SEQUENCE: 
	Result = LIST_WITH_PATH( FILENAME, PATHS )

 INPUTS: 
	FILENAME   = Name of file to be searched for.  It may contain wildcard
		     characters, e.g. "*.dat".

	PATHS	   = One or more default paths to use in the search in case
		     FILENAME does not contain a path itself.  The individual
		     paths are separated by commas, although in UNIX, colons
		     can also be used.  In other words, PATHS has the same
		     format as !PATH, except that commas can be used as a
		     separator regardless of operating system.  The current
		     directory is always searched first, unless the keyword
		     NOCURRENT is set.

		     A leading $ can be used in any path to signal that what
		     follows is an environmental variable, but the $ is not
		     necessary.    Environmental variables can themselves 
                    contain multiple paths.

 OUTPUTS: 
	The result of the function is a list of filenames.
 EXAMPLE:
	FILENAME = ''
	READ, 'File to open: ', FILENAME
	FILE = LIST_WITH_PATH( FILENAME, 'SERTS_DATA', '.fix' )
	IF FILE NE '' THEN ...
 PROCEDURE CALLS: 
	BREAK_PATH, CONCAT_DIR()
 Category    : 
	Utilities, Operating_system
 REVISION HISTORY:
	Version 1, William Thompson, GSFC, 3 November 1994
	Documentation modified Wayne Landsman HSTX  November 1994
	Assume since V5.5, vector call to FILE_SEARCH()  W. Landsman Sep 2006
       Restore pre-Sep 2006 behavior of not searching subdirectories 
                      W.Landsman. Feb 2007

(See $IDLUTILS_DIR/goddard/pro/misc/list_with_path.pro)

LSF_ROTATE:

 NAME:
     LSF_ROTATE:

 PURPOSE:
     Create a 1-d convolution kernel to broaden a spectrum from a rotating star

 EXPLANATION:
     Can be used to derive the broadening effect (line spread function; LSF) 
     due to  rotation on a synthetic stellar spectrum.     Assumes constant 
     limb darkening across the disk.

 CALLING SEQUENCE
     lsf = LSF_ROTATE(deltav, vsini, EPSILON=, VELGRID=)

 INPUT PARAMETERS:
    deltaV - numeric scalar giving the step increment (in km/s) in the output 
             rotation kernel.  
    Vsini - the rotational velocity projected  along the line of sight (km/s)

 OUTPUT PARAMETERS:
    LSF - The convolution kernel vector for the specified rotational velocity.
          The  number of points in LSF will be always be odd (the kernel is
          symmetric) and equal to  either ceil(2*Vsini/deltav) or 
          ceil(2*Vsini/deltav) +1 (whichever number is odd).    LSF will 
          always be of type FLOAT.

          To actually compute the broadening. the spectrum should be convolved
          with the rotational LSF. 
 OPTIONAL INPUT PARAMETERS:
    Epsilon - numeric scalar giving the limb-darkening coefficient, 
          default = 0.6 which is typical for  photospheric lines.    The
          specific intensity I at any angle theta from the specific intensity
          Icen at the center of the disk is given by:
  
          I = Icen*(1-epsilon*(1-cos(theta))
                    
 OPTIONAL OUTPUT PARAMETER:
     Velgrid - Vector with the same number of elements as LSF 
 EXAMPLE:
    (1) Plot the LSF for a star rotating at 90 km/s in both velocity space and
        for a central wavelength of 4300 A.    Compute the LSF every 3 km/s

       IDL> lsf = lsf_rotate(3,90,velgrid=vel)      ;LSF will contain 61 pts
       IDL> plot,vel,lsf                    ;Plot the LSF in velocity space
       IDL> wgrid = 4300*(1+vel/3e5)       ;Speed of light = 3e5 km/s
       IDL> oplot,wgrid,lsf                ;Plot in wavelength space

 NOTES:
    Adapted from rotin3.f in the SYNSPEC software of Hubeny & Lanz 
        .http://nova.astro.umd.edu/index.html    Also see Eq. 17.12 in 
    "The Observation and Analysis of Stellar Photospheres" by D. Gray (1992)
 REVISION HISTORY:
    Written,   W. Landsman                November 2001

(See $IDLUTILS_DIR/goddard/pro/astro/lsf_rotate.pro)

LUMDIST

 NAME: 
    LUMDIST
       
 PURPOSE: 
    Calculate luminosity distance (in Mpc) of an object given its redshift 
 EXPLANATION:
    The luminosity distance in the Friedmann-Robertson-Walker model is 
    taken from  Caroll, Press, and Turner (1992, ARAA, 30, 499), p. 511
    Uses a closed form (Mattig equation) to compute the distance when the 
    cosmological constant is zero.   Otherwise integrates the function using
    QSIMP.	
 CALLING SEQUENCE: 
    result = lumdist(z, [H0 = , k = , Omega_M =, Lambda0 = , q0 = ,/SILENT])
      
 INPUTS:
    z = redshift, positive scalar or vector

 OPTIONAL KEYWORD INPUTS: 
    /SILENT - If set, the program will not display adopted cosmological
        parameters at the terminal.
    H0: Hubble parameter  in km/s/Mpc, default is 70

        No more than two of the following four parameters should be
        specified.   None of them need be specified -- the adopted defaults
        are given.
    k - curvature constant, normalized to the closure density.   Default is
        0, indicating a flat universe
    Omega_m -  Matter density, normalized to the closure density, default
        is 0.3.   Must be non-negative
    Lambda0 - Cosmological constant, normalized to the closure density,
        default is 0.7
    q0 - Deceleration parameter, numeric scalar = -R*(R'')/(R')^2, default
        is -0.55
       
 OUTPUTS:
    The result of the function is the luminosity distance (in Mpc) for each 
    input value of z.

 EXAMPLE:
    (1) Plot the distance of a galaxy in Mpc as a function of redshift out 
        to z = 5.0, assuming the default cosmology (Omega_m=0.3, Lambda = 0.7,
        H0 = 70 km/s/Mpc)

        IDL> z = findgen(50)/10.
        IDL> plot,z,lumdist(z),xtit='z',ytit='Distance (Mpc)'

        Now overplot the relation for zero cosmological constant and 
        Omega_m=0.3
        IDL> oplot,z,lumdist(z,lambda=0,omega=0.3),linestyle=1
 COMMENTS:
    (1) Integrates using the IDL Astronomy Version procedure QSIMP.    (The 
    intrinsic IDL QSIMP function is not called because of its ridiculous
    restriction that only scalar arguments can be passed to the integrating
    function.)
    (2) Can fail to converge at high redshift for closed universes with
    non-zero lambda.   This can presumably be fixed by replacing QSIMP with
    an integrator that can handle a singularity 
 PROCEDURES CALLED:
    COSMO_PARAM, QSIMP   
 REVISION HISTORY:
    Written   W. Landsman        Raytheon ITSS       April 2000
    Avoid integer overflow for more than 32767 redshifts  July 2001
    Use double precision J. Moustakas/W. Landsman April 2008

(See $IDLUTILS_DIR/goddard/pro/astro/lumdist.pro)

MAG2FLUX

 NAME:
	MAG2FLUX
 PURPOSE:
	Convert from magnitudes to flux (ergs/s/cm^2/A). 
 EXPLANATION:
	Use FLUX2MAG() for the opposite direction.

 CALLING SEQUENCE:
	flux = mag2flux( mag, [ zero_pt, ABwave = ] )

 INPUTS:
	mag - scalar or vector of magnitudes

 OPTIONAL INPUT:
	zero_pt - scalar giving the zero point level of the magnitude.
		If not supplied then zero_pt = 21.1 (Code et al. 1976)
               Ignored if the ABwave keyword is set.

 OPTIONAL KEYWORD INPUT:
     ABwave - wavelength scalar or vector in Angstroms.   If supplied, then 
              the input vector, mag, is assumed to contain Oke AB magnitudes
              (Oke & Gunn 1983, ApJ, 266, 713)

 OUTPUT:
	flux - scalar or vector flux vector, in erg cm-2 s-1 A-1
              If the ABwave keyword is set, then the flux is given by

              f = 10^(-0.4*(mag +2.406 + 4*alog10(ABwave)))     

              Otherwise the flux is given by
              f =  10^(-0.4*(mag + zero_pt))

 EXAMPLE:
       Suppose one is given vectors of wavelengths and AB magnitudes, w (in
       Angstroms) and mag.   Plot the spectrum in erg cm-2 s-1 A-1

       IDL> plot, w, mag2flux(mag,ABwave = w)
 REVISION HISTORY:
	Written    J. Hill        STX Co.       1988
	Converted to IDL V5.0   W. Landsman   September 1997
       Added ABwave keyword,   W. Landsman   September 1998

(See $IDLUTILS_DIR/goddard/pro/astro/mag2flux.pro)

MAG2GEO()

 NAME:
      MAG2GEO()

 PURPOSE:
     Convert from geomagnetic to geographic coordinates

 EXPLANATION:
 
     Converts from GEOMAGNETIC (latitude,longitude) to GEOGRAPHIC (latitude,
    longitude).    (altitude remains the same)

 CALLING SEQUENCE:
       gcoord=mag2geo(mcoord)

 INPUT:
       mcoord = a 2-element array of magnetic [latitude,longitude], or an 
                array [2,n] of n such coordinates.

 KEYWORD INPUTS:
               None

 OUTPUT:
       a 2-element array of geographic [latitude,longitude], or an array [2,n]
            of n such coordinates                   

 COMMON BLOCKS:
               None

 EXAMPLES:
       IDL> gcoord=mag2geo([90,0])       ; coordinates of magnetic south pole
       IDL> print,gcoord
       79.300000      -71.409990

 MODIFICATION HISTORY:
       Written by Pascal Saint-Hilaire (Saint-Hilaire@astro.phys.ethz.ch), 
        May 2002

(See $IDLUTILS_DIR/goddard/pro/astro/mag2geo.pro)

MAKE_2D

 NAME:
       MAKE_2D
 PURPOSE:
       Change from 1-d indexing to 2-d indexing
 EXPLANATION:
       Convert an N element X vector, and an M element Y vector, into
       N x M arrays giving all possible combination of X and Y pairs.
       Useful for obtaining the X and Y positions of each element of
       a regular grid.

 CALLING SEQUENCE:
       MAKE_2D, X, Y, [ XX, YY ]

 INPUTS:
       X - N element vector of X positions
       Y - M element vector of Y positions

 OUTPUTS:
       XX - N x M element array giving the X position at each pixel
       YY - N x M element array giving the Y position of each pixel
               If only 2 parameters are supplied then X and Y will be
               updated to contain the output arrays

 EXAMPLE:
       To obtain the X and Y position of each element of a 30 x 15 array

       IDL> x = indgen(30)  &  y = indgen(15)     
       IDL> make_2d, x, y 
 REVISION HISTORY:
       Written,    Wayne Landsman    ST Systems Co.    May, 1988
       Added /NOZERO keyword       W. Landsman         Mar, 1991
       Converted to IDL V5.0   W. Landsman   September 1997
       Improved speed          P. Broos      July 2000

(See $IDLUTILS_DIR/goddard/pro/misc/make_2d.pro)

MAKE_ASTR

 NAME:
       MAKE_ASTR
 PURPOSE:
       Build an astrometry structure from input parameter values
 EXPLANATION:
       This structure can be subsequently placed in a FITS header with 
       PUTAST

 CALLING SEQUENCE:
       MAKE_ASTR, astr, CD = , DELT =, CRPIX =, CRVAL =, CTYPE =,
               LATPOLE = , LONGPOLE =, PV2_1 = PV2_2 = , PV2_3 =  

 OUTPUT PARAMETER:
       ASTR - Anonymous structure containing astrometry info.  See the 
              documentation for EXTAST for descriptions of the individual
              tags

 REQUIRED INPUT KEYWORDS
       CRPIX - 2 element vector giving X and Y coordinates of reference pixel
               (def = NAXIS/2).  VALUES MUST BE IN FITS CONVENTION (first pixel
               is [1,1]) AND NOT IDL CONVENTION (first pixel is [0,0]).
       CRVAL - 2 element double precision vector giving R.A. and DEC of 
               reference pixel in DEGREES
 OPTIONAL INPUT KEYWORDS
       CD -  2 x 2 array containing the astrometry parameters CD1_1 CD1_2
              in DEGREES/PIXEL                                CD2_1 CD2_2
       DELT - 2 element vector giving physical increment at reference pixel
              in DEGREES/PIXEL default = [-1.0D, 1.0D]/3600.  (1 arcsec/pixel)
       CTYPE - 2 element string vector giving projection types, default
              ['RA---TAN','DEC--TAN']
       LATPOLE - Scalar latitude of the north pole, default = 0
       LONGPOLE - scalar longitude of north pole, default = 180
                Note that the default value of 180 is valid only for zenithal
               projections; it should be set to PV2_1 for conic projections,
               and zero for other projections.
       PV2 - Vector of projection parameters.   Not required for some 
             projections (e.g. TAN) and optional for others (e.g. SIN).
             Usually a 2 element vector, but may contain up to 21 elements
             for the Zenithal Polynomial (ZPN) projection.   Corresponds to 
             the keywords PV2_1, PV2_2...  Defaults to 0.0

 NOTES:
       (1) An anonymous structure is created to avoid structure definition
               conflicts.    This is needed because some projection systems
               require additional dimensions (i.e. spherical cube
               projections require a specification of the cube face).
       (2) The name of the keyword for the CDELT parameter is DELT because
               the IDL keyword CDELT would conflict with the CD keyword
       (3) The astrometry structure definition was slightly modified in 
               July 2003; all angles are now double precision, and the 
               LATPOLE tag was added.   In April 2007 the CRPIX tag was also
               changed to double precision.
 REVISION HISTORY:
       Written by   W. Landsman              Mar. 1994
       Added LATPOLE, all angles double precision  W. Landsman July 2003
       Use PV2 keyword rather than PROJP1, PROJP2 W. Landsman May 2004
       Make .CRPIX tag double precision, change CDELT default to 1"/pixel
                      W. Landsman April 2007
        Default plate scale is now 1"/pixel (not 1 deg/pix)  WL  Oct. 2010
        Oct 2010 change should only apply when CD matrix not given 
                     M. Cushing/W.L.  Aug 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/make_astr.pro)

MATCH

 NAME:
       MATCH
 PURPOSE:
       Routine to match values in two vectors.

 CALLING SEQUENCE:
       match, a, b, suba, subb, [ COUNT =, /SORT, EPSILON =  ]

 INPUTS:
       a,b - two vectors to match elements, numeric or string data types

 OUTPUTS:
       suba - subscripts of elements in vector a with a match
               in vector b
       subb - subscripts of the positions of the elements in
               vector b with matchs in vector a.

       suba and subb are ordered such that a[suba] equals b[subb]

 OPTIONAL INPUT KEYWORD:
       /SORT - By default, MATCH uses two different algorithm: (1) the
               /REVERSE_INDICES keyword to HISTOGRAM is used for integer data,
               while (2) a sorting algorithm is used for non-integer data.  The
               histogram algorithm is usually faster, except when the input
               vectors are sparse and contain very large numbers, possibly
               causing memory problems.   Use the /SORT keyword to always use
               the sort algorithm.
       epsilon - if values are within epsilon, they are considered equal. Used only
               only for non-integer matching.  Note that input vectors should 
               be unique to within epsilon to provide one-to-one mapping.. 
               Default=0.

 OPTIONAL KEYWORD OUTPUT:
       COUNT - set to the number of matches, integer scalar

 SIDE EFFECTS:
       The obsolete system variable !ERR is set to the number of matches;
       however, the use !ERR is deprecated in favor of the COUNT keyword

 RESTRICTIONS:
       The vectors a and b should not have duplicate values within them.
       You can use rem_dup function to remove duplicate values
       in a vector

 EXAMPLE:
       If a = [3,5,7,9,11]   & b = [5,6,7,8,9,10]
       then
               IDL> match, a, b, suba, subb, COUNT = count

       will give suba = [1,2,3], subb = [0,2,4],  COUNT = 3
       and       a[suba] = b[subb] = [5,7,9]


 METHOD:
       For non-integer data types, the two input vectors are combined and
       sorted and the consecutive equal elements are identified.   For integer
       data types, the /REVERSE_INDICES keyword to HISTOGRAM of each array
       is used to identify where the two arrays have elements in common.
 HISTORY:
       D. Lindler  Mar. 1986.
       Fixed "indgen" call for very large arrays   W. Landsman  Sep 1991
       Added COUNT keyword    W. Landsman   Sep. 1992
       Fixed case where single element array supplied   W. Landsman Aug 95
       Use a HISTOGRAM algorithm for integer vector inputs for improved
             performance                W. Landsman         March 2000
       Work again for strings           W. Landsman         April 2000
       Use size(/type)                  W. Landsman         December 2002
       Work for scalar integer input    W. Landsman         June 2003
       Assume since V5.4, use COMPLEMENT to WHERE() W. Landsman Apr 2006
       Added epsilon keyword            Kim Tolbert         March 14, 2008

(See $IDLUTILS_DIR/goddard/pro/misc/match.pro)

MATCH2

 NAME:
       MATCH2
 PURPOSE:
       Routine to cross-match values in two vectors (including non-matches)
 EXPLANATION:
       This procedure *appears* similar to MATCH of the IDL astronomy
       library.  However, this routine is quite different in that it
       reports an index value for each element of the input arrays.
       In other words, while MATCH reports the *existence* of
       matching elements in each array, MATCH2 reports explicitly
       *which* elements match.

       Furthermore, while MATCH reports only unique matching
       elements, MATCH2 will always report a cross-match for every
       element in each array, even if it is a repeat.

       In cases where no match was found, an index of -1 is
       reported.  

 CALLING SEQUENCE:
       match2, a, b, suba, subb

 INPUTS:
       a,b - two vectors to match elements, numeric or string data types

 OUTPUTS:
       suba - vector with same number of elements as A, such that
              A EQ B[SUBA], except non-matches which are indicated
              by SUBA EQ -1
       subb - vector with same number of elements as B, such that
              B EQ A[SUBB], except non-matches which are indicated
              by SUBB EQ -1


 RESTRICTIONS:
 
       The vectors A and B are allowed to have duplicates in them,
       but for matching purposes, only the first one found will
       be reported.

 EXAMPLE:
      A = [0,7,14,23,24,30]
      B = [7,8,14,25,14]
      IDL> match2, a, b, suba, subb
     --> suba = [ -1 ,  0,  4,  -1, -1, -1 ]
     (indicates that A[1] matches B[1] and A[3] matches B[2])
     --> subb = [  1 , -1,  2,  -1,  2 ]
     (indicates that B[1] matches A[1] and B[2] matches A[3])

  Compare to the results of the original MATCH procedure,
    
      IDL> match, a, b, suba, subb
     --> suba = [  1,  3]
  (indicates that A[1] and A[3] match elements in B, but not which ones)
     --> subb = [  1,  2]
  (indicates that B[1] and B[2] match elements in A, but not which ones)

 MODIFICATION HISTORY
   Derived from the IDL Astronomy Library MATCH, 14 Feb 2007
   Updated documentation, 17 Jul 2007
   More updated documentation (example), 03 Sep 2007

(See $IDLUTILS_DIR/goddard/pro/misc/match2.pro)

MAX_ENTROPY

 NAME:
	MAX_ENTROPY

 PURPOSE:
	Deconvolution of data by Maximum Entropy analysis, given the PSF
 EXPLANATION:
	Deconvolution of data by Maximum Entropy analysis, given the 
	instrument point spread response function (spatially invariant psf).
	Data can be an observed image or spectrum, result is always positive.
	Default is convolutions using FFT (faster when image size = power of 2).

 CALLING SEQUENCE:
	for i=1,Niter do begin
	Max_Entropy, image_data, psf, image_deconv, multipliers, FT_PSF=psf_ft

 INPUTS:
	data = observed image or spectrum, should be mostly positive,
					with mean sky (background) near zero.
	psf = Point Spread Function of instrument (response to point source,
							must sum to unity).
	deconv = result of previous call to Max_Entropy,
	multipliers = the Lagrange multipliers of max.entropy theory
		(on first call, set = 0, giving flat first result).

 OUTPUTS:
	deconv = deconvolution result of one more iteration by Max_Entropy.
	multipliers = the Lagrange multipliers saved for next iteration.

 OPTIONAL INPUT KEYWORDS:
	FT_PSF = passes (out/in) the Fourier transform of the PSF,
		so that it can be reused for the next time procedure is called,
      /NO_FT overrides the use of FFT, using the IDL function convol() instead.
      /LINEAR switches to Linear convergence mode, much slower than the
		default Logarithmic convergence mode.
	LOGMIN = minimum value constraint for taking Logarithms (default=1.e-9).
 EXTERNAL CALLS:
	function convolve( image, psf ) for convolutions using FFT or otherwise.
 METHOD:
	Iteration with PSF to maximize entropy of solution image with
	constraint that the solution convolved with PSF fits data image.
	Based on paper by Hollis, Dorband, Yusef-Zadeh, Ap.J. Feb.1992,
	which refers to Agmon, Alhassid, Levine, J.Comp.Phys. 1979.

       A more elaborate image deconvolution program using maximum entropy is 
       available at 
       http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/image/image_deconvolve.pro
 HISTORY:  
	written by Frank Varosi at NASA/GSFC, 1992.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/image/max_entropy.pro)

MAX_LIKELIHOOD

 NAME:
	MAX_LIKELIHOOD

 PURPOSE:
	Maximum likelihood deconvolution of an image or a spectrum.
 EXPLANATION:
 	Deconvolution of an observed image (or spectrum) given the 
	instrument point spread response function (spatially invariant psf).
	Performs iteration based on the Maximum Likelihood solution for
	the restoration of a blurred image (or spectrum) with additive noise.
	Maximum Likelihood formulation can assume Poisson noise statistics
	or Gaussian additive noise, yielding two types of iteration.

 CALLING SEQUENCE:
	for i=1,Niter do Max_Likelihood, data, psf, deconv, FT_PSF=psf_ft

 INPUTS PARAMETERS:
	data = observed image or spectrum, should be mostly positive,
				with mean sky (background) near zero.
	psf = Point Spread Function of the observing instrument,
				(response to a point source, must sum to unity).
 INPUT/OUTPUT PARAMETERS:
	deconv = as input: the result of previous call to Max_Likelihood,
		(initial guess on first call, default = average of data),
		as output: result of one more iteration by Max_Likelihood.
	Re_conv = (optional) the current deconv image reconvolved with PSF
		for use in next iteration and to check convergence.

 OPTIONAL INPUT KEYWORDS:
      /GAUSSIAN causes max-likelihood iteration for Gaussian additive noise
		to be used,  otherwise the default is Poisson statistics.
	FT_PSF = passes (out/in) the Fourier transform of the PSF,
		so that it can be reused for the next time procedure is called,
      /NO_FT overrides the use of FFT, using the IDL function convol() instead.
	POSITIVITY_EPS = value of epsilon passed to function positivity,
			default = -1 which means no action (identity).
	UNDERFLOW_ZERO = cutoff to consider as zero, if numbers less than this.

 EXTERNAL CALLS:
	function convolve( image, psf ) for convolutions using FFT or otherwise.
	function positivity( image, EPS= ) to make image positive.

 METHOD:
	Maximum Likelihood solution is a fixed point of an iterative eq.
	(derived by setting partial derivatives of Log(Likelihood) to zero).
	Poisson noise case was derived by Richardson(1972) & Lucy(1974).
	Gaussian noise case is similar with subtraction instead of division.
 NOTES:
       WARNING: The Poisson case may not conserve flux for an odd image size.  
       This behavior is being investigated.
 HISTORY:
	written: Frank Varosi at NASA/GSFC, 1992.
	F.V. 1993, added optional arg. Re_conv (to avoid doing it twice).
	Converted to IDL V5.0   W. Landsman   September 1997
       Use COMPLEMENT keyword to WHERE()   W. Landsman  Jan 2008

(See $IDLUTILS_DIR/goddard/pro/image/max_likelihood.pro)

MEANCLIP

 NAME:
       MEANCLIP

 PURPOSE:
       Computes an iteratively sigma-clipped mean on a data set
 EXPLANATION:
       Clipping is done about median, but mean is returned.
       Called by SKYADJ_CUBE

 CATEGORY:
       Statistics

 CALLING SEQUENCE:
       MEANCLIP, Data, Mean, [ Sigma, SUBS =
              CLIPSIG=, MAXITER=, CONVERGE_NUM=, /VERBOSE, /DOUBLE ]

 INPUT POSITIONAL PARAMETERS:
       Data:     Input data, any numeric array
       
 OUTPUT POSITIONAL PARAMETERS:
       Mean:     N-sigma clipped mean.
       Sigma:    Standard deviation of remaining pixels.

 INPUT KEYWORD PARAMETERS:
       CLIPSIG:  Number of sigma at which to clip.  Default=3
       MAXITER:  Ceiling on number of clipping iterations.  Default=5
       CONVERGE_NUM:  If the proportion of rejected pixels is less
           than this fraction, the iterations stop.  Default=0.02, i.e.,
           iteration stops if fewer than 2% of pixels excluded.
       /VERBOSE:  Set this flag to get messages.
       /DOUBLE - if set then perform all computations in double precision.
                 Otherwise double precision is used only if the input
                 data is double
 OUTPUT KEYWORD PARAMETER:
       SUBS:     Subscript array for pixels finally used.


 MODIFICATION HISTORY:
       Written by:     RSH, RITSS, 21 Oct 98
       20 Jan 99 - Added SUBS, fixed misplaced paren on float call, 
                   improved doc.  RSH
       Nov 2005   Added /DOUBLE keyword, check if all pixels are removed  
                  by clipping W. Landsman

(See $IDLUTILS_DIR/goddard/pro/math/meanclip.pro)

MEDARR

 NAME:
       MEDARR
 PURPOSE:
       Compute the median at each pixel across a set of 2-d images
 EXPLANATION:
       Each pixel in the output array contains  the median of the 
       corresponding pixels in the input arrays.   Useful, for example to 
       combine a stack of CCD images, while removing cosmic ray hits.

       This routine became partially obsolete in V5.6 with the introduction
       of the DIMENSION keyword to the intrinsic MEDIAN() function.   However,
       it is  still useful if a input mask is needed (though it is much 
       faster to set invalid pixels to NaN values.)
 CALLING SEQUENCE:
       MEDARR, inarr, outarr, [ mask, output_mask ]
 INPUTS:
       inarr  -- A three dimensional array containing the input arrays to 
                 combine together.  Each of the input arrays must be two 
                 dimensional and must have the same dimensions.  These arrays
                 should then be stacked together into a single 3-D array,
                 creating INARR.

 OPTIONAL INPUT:
       mask   -- Same structure as inarr, byte array with 1b where
                 pixels are to be included, 0b where they are to be
                 excluded.    For floating point images, it is much faster to 
                 set masked pixels in inarr equal to !VALUES.F_NAN (see below),
                 rather than use the mask parameter.
                
 OUTPUTS:
       outarr -- The output array.  It will have dimensions equal to the
                 first two dimensions of the input array.

 OPTIONAL OUPUT:
       output_mask -- Same structure as outarr, byte array with 1b
                      pixels are valid, 0b where all the input pixels
                      have been masked out.
 RESTRICTIONS:
        This procedure was *SLOW* when using the Mask parameter because it has
        to loop over  each pixel of the image.  

 EXAMPLE:
       Suppose one wants to combine three floating point 1024 x 1024 bias 
       frames which have been read into the IDL variables im1,im2,im3

       IDL> bigim = fltarr(1024,1024,3)        ;Create big array to hold images
       IDL> bigim(0,0,0) = im1 & bigim(0,0,1) = im2 & bigim(0,0,2) = im2  
       IDL> medarr, bigim, avgbias

       The variable avgbias will be the desired 1024x 1024 float image.
 PROCEDURE:
       If the MASK parameter is not set, then MEDARR is just a wrapper for 
       MEDIAN(/EVEN, dimension = 3).    If the MASK parameter is set,
       a scalar median function over the third dimension is looped over 
       each pixel of the first two dimensions.   The /EVEN keyword is used
       with MEDIAN (which averages the two middle values), since this avoids 
       biasing the output for an even number of images.

       Any values set to NAN (not a number) are ignored when computing the
       median.    If all values for a pixel location are NAN, then the median
       is also returned as NAN.

 MODIFICATION HISTORY:
       Written by Michael R. Greason, STX, 12 June 1990.
       Don't use MEDIAN function for even number of images.
          W. Landsman Sep 1996
       Mask added.  RS Hill, HSTX, 13 Mar. 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Use /EVEN keyword to MEDIAN    W. Landsman  September 1997
       Rearranged code for faster execution   W. Landsman January 1998
       Faster execution for odd number of images   W. Landsman July 2000
       V5.4 fix for change in SIZE() definition of undefined variable 
                W. Landsman/E. Young   May 2001
       Use MEDIAN(/DIMEN) for V5.6 or later   W. Landsman   November 2002
       Use keyword_set() instead of ARG_present() to test for presence of mask
           parameter  D. Hanish/W. Landsman   June 2003
       Assume since V5.6  W. Landsman  Feb 2004

(See $IDLUTILS_DIR/goddard/pro/image/medarr.pro)

MEDSMOOTH

 NAME:
       MEDSMOOTH

 PURPOSE:
       Median smoothing of a vector, including points near its ends.

 CALLING SEQUENCE:
       SMOOTHED = MEDSMOOTH( VECTOR, WINDOW_WIDTH )

 INPUTS:
       VECTOR  = The (1-d numeric) vector to be smoothed
       WINDOW = Odd integer giving the full width of the window over which 
               the median is determined for each point.     (If WINDOW is
               specified as an even number, then the effect is the same as
               using WINDOW+1)   

 OUTPUT:
       Function returns the smoothed vector

 PROCEDURE:
       Each point is replaced by the median of the nearest WINDOW of points.
       The width of the window shrinks towards the ends of the vector, so that
       only the first and last points are not filtered. These points are 
       replaced by forecasting from smoothed interior points.

 EXAMPLE:
       Create a vector with isolated high points near its ends
       IDL> a = randomn(seed,40) & a[1] = 10  & a[38] = 10
       Now do median smoothing with a 7 point window 
       IDL> b = medsmooth(a,7)
       Note that, unlike MEDIAN(), that MEDSMOOTH will remove the isolated
       high points near the ends.
 REVISION HISTORY:
       Written, H. Freudenreich, STX, 12/89
       H.Freudenreich, 8/90: took care of end-points by shrinking window.
       Speed up using vector median when possible  W. Landsman February 2002

(See $IDLUTILS_DIR/goddard/pro/robust/medsmooth.pro)

MINF_BRACKET

 NAME:
       MINF_BRACKET
 PURPOSE:
       Bracket a local minimum of a 1-D function with 3 points,
 EXPLANATION:
       Brackets a local minimum of a 1-d function with 3 points,
       thus ensuring that a minimum exists somewhere in the interval.
       This routine assumes that the function has a minimum somewhere....
       Routine can also be applied to a scalar function of many variables,
       for such case the local minimum in a specified direction is bracketed,
       This routine is called by minF_conj_grad, to bracket minimum in the 
       direction of the conjugate gradient of function of many variables
 CALLING EXAMPLE:
       xa=0  & xb=1                                    
       minF_bracket, xa,xb,xc, fa,fb,fc, FUNC_NAME="name"      ;for 1-D func.
  or:
       minF_bracket, xa,xb,xc, fa,fb,fc, FUNC="name",     $
                                         POINT=[0,1,1],   $
                                         DIRECTION=[2,1,1]     ;for 3-D func.
 INPUTS:
       xa = scalar, guess for point bracketing location of minimum.
       xb = scalar, second guess for point bracketing location of minimum.
 KEYWORDS:
       FUNC_NAME = function name (string)
               Calling mechanism should be:  F = func_name( px )
               where:
                       px = scalar or vector of independent variables, input.
                       F = scalar value of function at px.
       POINT_NDIM = when working with function of N variables,
               use this keyword to specify the starting point in N-dim space.
               Default = 0, which assumes function is 1-D.
       DIRECTION = when working with function of N variables,
               use this keyword to specify the direction in N-dim space
               along which to bracket the local minimum, (default=1 for 1-D).
               (xa,xb,xc) are then relative distances from POINT_NDIM.
 OUTPUTS:
       xa,xb,xc = scalars, 3 points which bracket location of minimum,
               that is, f(xb) < f(xa) and f(xb) < f(xc), so minimum exists.
               When working with function of N variables
               (xa,xb,xc) are then relative distances from POINT_NDIM,
               in the direction specified by keyword DIRECTION,
               with scale factor given by magnitude of DIRECTION.
 OPTIONAL OUTPUT:
       fa,fb,fc = value of function at 3 points which bracket the minimum,
                       again note that fb < fa and fb < fc if minimum exists.
 PROCEDURE:
       algorithm from Numerical Recipes (by Press, et al.), sec.10.1 (p.281).
 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC 1992.
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/minf_bracket.pro)

MINF_CONJ_GRAD

 NAME:
        MINF_CONJ_GRAD
 PURPOSE:
       Find the local minimum of a scalar function using conjugate gradient
 EXPLANATION:
       Find the local minimum of a scalar function of several variables using 
       the Conjugate Gradient method (Fletcher-Reeves-Polak-Ribiere algorithm).
       Function may be anything with computable partial derivatives.
       Each call to minF_conj_grad performs one iteration of algorithm,
       and returns an N-dim point closer to the local minimum of function.
 CALLING EXAMPLE:
       p_min = replicate( 1, N_dim )
       minF_conj_grad, p_min, f_min, conv_factor, FUNC_NAME="name",/INITIALIZE

       while (conv_factor GT 0) do begin
               minF_conj_grad, p_min, f_min, conv_factor, FUNC_NAME="name"
       endwhile
 INPUTS:
       p_min = vector of independent variables, location of minimum point
               obtained from previous call to minF_conj_grad, (or first guess).
 KEYWORDS:
       FUNC_NAME = function name (string)
               Calling mechanism should be:  F = func_name( px, gradient )
         where:
               F = scalar value of function at px.
               px = vector of independent variables, input.
               gradient = vector of partial derivatives of the function
                       with respect to independent variables, evaluated at px.
                       This is an optional output parameter:
                       gradient should not be calculated if parameter is not
                       supplied in call (Unless you want to waste some time).
      /INIT must be specified on first call (whenever p_min is a guess),
                       to initialize the iteration scheme of algorithm.
      /USE_DERIV causes the directional derivative of function to be used
                       in the 1-D minimization part of algorithm
                       (default is not to use directional derivative).
       TOLERANCE = desired accuracy of minimum location, default=sqrt(1.e-7).
      /QUADRATIC runs simpler version which works only for quadratic function.
 OUTPUTS:
       p_min = vector giving improved solution for location of minimum point.
       f_min = value of function at p_min.
       conv_factor = gives the current rate of convergence (change in value),
                       iteration should be stopped when rate gets near zero.
 EXTERNAL CALLS:
       pro minF_bracket,  to find 3 points which bracket the minimum in 1-D.
       pro minF_parabolic,  to find minimum point in 1-D.
       pro minF_parabol_D,  to find minimum point in 1-D, using derivatives.
 COMMON BLOCKS:
       common minf_conj_grad, grad_conj, grad_save, gs_norm
       (to keep conjugate gradient, gradient and norm from previous iteration)
 PROCEDURE:
       Algorithm adapted from Numerical Recipes, sec.10.6 (p.305).
       Conjugate gradient is computed from gradient, which then gives
       the best direction (in N-dim space) in which to proceed to find
       the minimum point. The function is then minimized along
       this direction of conjugate gradient (a 1-D minimization).
       The algorithm is repeated starting at the new point by calling again.
 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC 1992.
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/minf_conj_grad.pro)

MINF_PARABOLIC

 NAME:
       MINF_PARABOLIC
 PURPOSE:
       Minimize a function using Brent's method with parabolic interpolation
 EXPLANATION:
       Find a local minimum of a 1-D function up to specified tolerance.
       This routine assumes that the function has a minimum nearby.
       (recommend first calling minF_bracket, xa,xb,xc, to bracket minimum).
       Routine can also be applied to a scalar function of many variables,
       for such case the local minimum in a specified direction is found,
       This routine is called by minF_conj_grad, to locate minimum in the 
       direction of the conjugate gradient of function of many variables.

 CALLING EXAMPLES:
       minF_parabolic, xa,xb,xc, xmin, fmin, FUNC_NAME="name"  ;for 1-D func.
  or:
       minF_parabolic, xa,xb,xc, xmin, fmin, FUNC="name", $
                                         POINT=[0,1,1],   $
                                         DIRECTION=[2,1,1]     ;for 3-D func.
 INPUTS:
       xa,xb,xc = scalars, 3 points which bracket location of minimum,
               that is, f(xb) < f(xa) and f(xb) < f(xc), so minimum exists.
               When working with function of N variables
               (xa,xb,xc) are then relative distances from POINT_NDIM,
               in the direction specified by keyword DIRECTION,
               with scale factor given by magnitude of DIRECTION.
 INPUT KEYWORDS:
      FUNC_NAME = function name (string)
               Calling mechanism should be:  F = func_name( px )
               where:
                       px = scalar or vector of independent variables, input.
                       F = scalar value of function at px.

      POINT_NDIM = when working with function of N variables,
               use this keyword to specify the starting point in N-dim space.
               Default = 0, which assumes function is 1-D.
      DIRECTION = when working with function of N variables,
               use this keyword to specify the direction in N-dim space
               along which to bracket the local minimum, (default=1 for 1-D).
               (xa, xb, xc, x_min are then relative distances from POINT_NDIM)
      MAX_ITER = maximum allowed number iterations, default=100.
      TOLERANCE = desired accuracy of minimum location, default=sqrt(1.e-7).
 OUTPUTS:
       xmin = estimated location of minimum.
               When working with function of N variables,
               xmin is the relative distance from POINT_NDIM,
               in the direction specified by keyword DIRECTION,
               with scale factor given by magnitude of DIRECTION,
               so that min. Loc. Pmin = Point_Ndim + xmin * Direction.
       fmin = value of function at xmin (or Pmin).
 PROCEDURE:
       Brent's method to minimize a function by using parabolic interpolation.
       Based on function BRENT in Numerical Recipes in FORTRAN (Press et al. 
       1992),  sec.10.2 (p. 397).
 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC 1992.
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/minf_parabolic.pro)

MINF_PARABOL_D

 NAME:
       MINF_PARABOL_D
 PURPOSE:
       Minimize a function using a modified  Brent's method with derivatives
 EXPLANATION:
       Based on the procedure DBRENT in Numerical Recipes by Press et al.
       Finds a local minimum of a 1-D function up to specified tolerance,
       using the first derivative of function in the algorithm.
       This routine assumes that the function has a minimum nearby.
       (recommend first calling minF_bracket, xa,xb,xc, to bracket minimum).
       Routine can also be applied to a scalar function of many variables,
       for such case the local minimum in a specified direction is found,
       This routine is called by minF_conj_grad, to locate minimum in the 
       direction of the conjugate gradient of function of many variables.

 CALLING EXAMPLES:
       minF_parabol_D, xa,xb,xc, xmin, fmin, FUNC_NAME="name"  ;for 1-D func.
  or:
       minF_parabol_D, xa,xb,xc, xmin, fmin, FUNC="name", $
                                         POINT=[0,1,1],   $
                                         DIRECTION=[2,1,1]     ;for 3-D func.
 INPUTS:
       xa,xb,xc = scalars, 3 points which bracket location of minimum,
               that is, f(xb) < f(xa) and f(xb) < f(xc), so minimum exists.
               When working with function of N variables
               (xa,xb,xc) are then relative distances from POINT_NDIM,
               in the direction specified by keyword DIRECTION,
               with scale factor given by magnitude of DIRECTION.
 KEYWORDS:
       FUNC_NAME = function name (string)
               Calling mechanism should be:  F = func_name( px, gradient )
               where:
                       px = scalar or vector of independent variables, input.
                       F = scalar value of function at px.
                       gradient = derivative of function, a scalar if 1-D,
                               a gradient vector if N-D,
                               (should only be computed if arg. is present).

       POINT_NDIM = when working with function of N variables,
               use this keyword to specify the starting point in N-dim space.
               Default = 0, which assumes function is 1-D.
       DIRECTION = when working with function of N variables,
               use this keyword to specify the direction in N-dim space
               along which to bracket the local minimum, (default=1 for 1-D).
               (xa, xb, xc, x_min are then relative distances from POINT_NDIM)
       MAX_ITER = maximum allowed number iterations, default=100.
       TOLERANCE = desired accuracy of minimum location, default=sqrt(1.e-7).

 OUTPUTS:
       xmin = estimated location of minimum.
               When working with function of N variables,
               xmin is the relative distance from POINT_NDIM,
               in the direction specified by keyword DIRECTION,
               with scale factor given by magnitude of DIRECTION,
               so that min. Loc. Pmin = Point_Ndim + xmin * Direction.
       fmin = value of function at xmin (or Pmin).
 PROCEDURE:
       Brent's method to minimize a function by using parabolic interpolation
       and using first derivative of function,
       from Numerical Recipes (by Press, et al.), sec.10.3 (p.287),
 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC 1992.

(See $IDLUTILS_DIR/goddard/pro/math/minf_parabol_d.pro)

MINMAX

 NAME:
      MINMAX
 PURPOSE:
      Return a 2 element array giving the minimum and maximum of an array
 EXPLANATION:
      Using MINMAX() is faster than doing a separate MAX and MIN.

      The procedure MAXMIN in http://www.idlcoyote.com/programs/maxmin.pro
      has a similar purpose but uses a procedure call rather than a function.
 CALLING SEQUENCE:
      value = minmax( array, [subs, /NAN, DIMEN= ] )
 INPUTS:
      array - an IDL numeric scalar, vector or array.

 OUTPUTS:
      value = a two element vector (if DIMEN is not supplied)
            value[0] = minimum value of array
            value[1] = maximum value of array

            If the DIMEN keyword is supplied then value will be a 2 x N element
            array where N is the number of elements in the specified
            dimension
              
 OPTIONAL OUTPUT PARAMETER:
       subs - two-dimensional vector; the first element gives the subscript
              of the minimum value, the second element gives the subscript
              of the maximum value.     

 OPTIONAL INPUT KEYWORD:
      /NAN   - Set this keyword to cause the routine to check for occurrences
            of the IEEE floating-point value NaN in the input data.  Elements 
            with the value NaN are treated as missing data.

      DIMEN -  integer (either 1 or 2) specifying which dimension of a 2-d 
            array to  take the minimum and maximum.   Note that (unlike the
            DIMENSION keyword to the MIN() function) DIMEN is only valid
            for a 2-d array, larger dimensions are  not supported.  
 EXAMPLE:
     (1)  Print the minimum and maximum of an image array, im
 
            IDL> print, minmax( im )

     (2) Given a 2-dimension array of (echelle) wavelengths w, print the
         minimum and maximum of each order

         print,minmax(w,dimen=1)

 PROCEDURE:
      The MIN function is used with the MAX keyword

 REVISION HISTORY:
      Written W. Landsman                January, 1990
      Added NaN keyword.      M. Buie       June 1998
      Added DIMEN keyword    W. Landsman  January 2002
      Added SUBSCRIPT_MIN and SUBSCRIPT_MAX  BT Jan 2005
      Added optional subs output parameter  W. Landsman July 2009

(See $IDLUTILS_DIR/goddard/pro/misc/minmax.pro)

MKHDR

 NAME:
       MKHDR
 PURPOSE:
       Make a minimal primary (or IMAGE extension) FITS header
 EXPLANATION:
       If an array is supplied,  then the created FITS header will be 
       appropriate to the supplied array.  Otherwise, the user can specify 
       the dimensions and datatype.

 CALLING SEQUENCE:
       MKHDR, header                   ;Prompt for image size and type
               or
       MKHDR, header, im, [ /IMAGE, /EXTEND ]
               or
       MKHDR, header, type, naxisx, [/IMAGE, /EXTEND ]         

 OPTIONAL INPUTS:
       IM - If IM is a vector or array then the header will be made
               appropriate to the size and type of IM.  IM does not have
               to be the actual data; it can be a dummy array of the same
               type and size as the data.    Set IM = '' to create a dummy
               header with NAXIS = 0. 
       TYPE - If more than 2 parameters are supplied, then the second parameter
               is interpreted as an integer giving the IDL datatype e.g. 
               1 - LOGICAL*1, 2 - INTEGER*2, 4 - REAL*4, 3 - INTEGER*4
       NAXISX - Vector giving the size of each dimension (NAXIS1, NAXIS2, 
               etc.).  

 OUTPUT:
       HEADER - image header, (string array) with required keywords
               BITPIX, NAXIS, NAXIS1, ... Further keywords can be added
               to the header with SXADDPAR. 

 OPTIONAL INPUT KEYWORDS:
       /IMAGE   = If set, then a minimal header for a FITS IMAGE extension
               is created.    An IMAGE extension header is identical to
               a primary FITS header except the first keyword is 
               'XTENSION' = 'IMAGE' instead of 'SIMPLE  ' = 'T'
       /EXTEND  = If set, then the keyword EXTEND is inserted into the file,
               with the value of "T" (true).    The EXTEND keyword must be
               included in a primary header, if the FITS file contains 
               extensions.

 RESTRICTIONS:
       (1)  MKHDR should not be used to make an STSDAS header or a FITS
               ASCII or Binary Table extension header.   Instead use

               SXHMAKE - to create a minimal STSDAS header
               FXBHMAKE - to create a minimal FITS binary table header
               FTCREATE - to create a minimal FITS ASCII table header

       (2)  Any data already in the header before calling MKHDR
               will be destroyed.
 EXAMPLE:
       Create a minimal FITS header, Hdr, for a 30 x 40 x 50 INTEGER*2 array

             IDL> mkhdr, Hdr, 2, [30,40,50]

       Alternatively, if the array already exists as an IDL variable, Array,

              IDL> mkhdr, Hdr, Array

 PROCEDURES CALLED:
       SXADDPAR, GET_DATE

 REVISION HISTORY:
       Written November, 1988               W. Landsman
       May, 1990, Adapted for IDL Version 2.0, J. Isensee
       Aug, 1997, Use SYSTIME(), new DATE format  W. Landsman
       Converted to IDL V5.0   W. Landsman   September 1997
       Allow unsigned data types    W. Landsman   December 1999
       Set BZERO = 0 for unsigned integer data  W. Landsman January 2000
       EXTEND keyword must immediately follow last NAXISi W. Landsman Sep 2000
       Add FITS definition COMMENT to primary headers W. Landsman Oct. 2001
       Allow (nonstandard) 64 bit integers   W. Landsman  Feb. 2003

(See $IDLUTILS_DIR/goddard/pro/fits/mkhdr.pro)

MLINMIX_ERR

   NAME:
     MLINMIX_ERR
   PURPOSE:
      Bayesian approach to multiple linear regression with errors in  X and Y
   EXPLANATION:
 PERFORM LINEAR REGRESSION OF Y ON X WHEN THERE ARE MEASUREMENT
 ERRORS IN BOTH VARIABLES. THE REGRESSION ASSUMES :

                 ETA = ALPHA + BETA ## XI + EPSILON
                 X = XI + XERR
                 Y = ETA + YERR

 HERE, (ALPHA, BETA) ARE THE REGRESSION COEFFICIENTS, EPSILON IS THE
 INTRINSIC RANDOM SCATTER ABOUT THE REGRESSION, XERR IS THE
 MEASUREMENT ERROR IN X, AND YERR IS THE MEASUREMENT ERROR IN
 Y. EPSILON IS ASSUMED TO BE NORMALLY-DISTRIBUTED WITH MEAN ZERO AND
 VARIANCE SIGSQR. XERR AND YERR ARE ASSUMED TO BE
 NORMALLY-DISTRIBUTED WITH MEANS EQUAL TO ZERO, COVARIANCE MATRICES
 XVAR^2 FOR X, VARIANCES YSIG^2 FOR Y, AND COVARIANCE VECTORS
 XYCOV. THE DISTRIBUTION OF XI IS MODELLED AS A MIXTURE OF NORMALS,
 WITH GROUP PROPORTIONS PI, MEANS MU, AND COVARIANCES T. BAYESIAN
 INFERENCE IS EMPLOYED, AND A STRUCTURE CONTAINING RANDOM DRAWS FROM
 THE POSTERIOR IS RETURNED. CONVERGENCE OF THE MCMC TO THE POSTERIOR
 IS MONITORED USING THE POTENTIAL SCALE REDUCTION FACTOR (RHAT,
 GELMAN ET AL.2004). IN GENERAL, WHEN RHAT < 1.1 THEN APPROXIMATE
 CONVERGENCE IS REACHED.

 SIMPLE NON-DETECTIONS ON Y MAY ALSO BE INCLUDED

 AUTHOR : BRANDON C. KELLY, STEWARD OBS., JULY 2006

 INPUTS :

   X - THE OBSERVED INDEPENDENT VARIABLES. THIS SHOULD BE AN
       [NX, NP]-ELEMENT ARRAY.
   Y - THE OBSERVED DEPENDENT VARIABLE. THIS SHOULD BE AN NX-ELEMENT
       VECTOR.

 OPTIONAL INPUTS :

   XVAR - THE COVARIANCE MATRIX OF THE X ERRORS, AND
          [NX,NP,NP]-ELEMENT ARRAY. XVAR[I,*,*] IS THE COVARIANCE
          MATRIX FOR THE ERRORS ON X[I,*]. THE DIAGONAL OF
          XVAR[I,*,*] MUST BE GREATER THAN ZERO FOR EACH DATA POINT.
   YVAR - THE VARIANCE OF THE Y ERRORS, AND NX-ELEMENT VECTOR. YVAR
          MUST BE GREATER THAN ZERO.
   XYCOV - THE VECTOR OF COVARIANCES FOR THE MEASUREMENT ERRORS
           BETWEEN X AND Y.
   DELTA - AN NX-ELEMENT VECTOR INDICATING WHETHER A DATA POINT IS
           CENSORED OR NOT. IF DELTA[i] = 1, THEN THE SOURCE IS
           DETECTED, ELSE IF DELTA[i] = 0 THE SOURCE IS NOT DETECTED
           AND Y[i] SHOULD BE AN UPPER LIMIT ON Y[i]. NOTE THAT IF
           THERE ARE CENSORED DATA POINTS, THEN THE
           MAXIMUM-LIKELIHOOD ESTIMATE (THETA) IS NOT VALID. THE
           DEFAULT IS TO ASSUME ALL DATA POINTS ARE DETECTED, IE,
           DELTA = REPLICATE(1, NX).
   SILENT - SUPPRESS TEXT OUTPUT.
   MINITER - MINIMUM NUMBER OF ITERATIONS PERFORMED BY THE GIBBS
             SAMPLER. IN GENERAL, MINITER = 5000 SHOULD BE SUFFICIENT
             FOR CONVERGENCE. THE DEFAULT IS MINITER = 5000. THE
             GIBBS SAMPLER IS STOPPED AFTER RHAT < 1.1 FOR ALPHA,
             BETA, AND SIGMA^2, AND THE NUMBER OF ITERATIONS
             PERFORMED IS GREATER THAN MINITER.
   MAXITER - THE MAXIMUM NUMBER OF ITERATIONS PERFORMED BY THE
             MCMC. THE DEFAULT IS 1D5. THE GIBBS SAMPLER IS STOPPED
             AUTOMATICALLY AFTER MAXITER ITERATIONS.
   NGAUSS - THE NUMBER OF GAUSSIANS TO USE IN THE MIXTURE
            MODELLING. THE DEFAULT IS 3. 

 OUTPUT :

    POST - A STRUCTURE CONTAINING THE RESULTS FROM THE GIBBS
           SAMPLER. EACH ELEMENT OF POST IS A DRAW FROM THE POSTERIOR
           DISTRIBUTION FOR EACH OF THE PARAMETERS.

             ALPHA - THE CONSTANT IN THE REGRESSION.
             BETA - THE SLOPES OF THE REGRESSION.
             SIGSQR - THE VARIANCE OF THE INTRINSIC SCATTER.
             PI - THE GAUSSIAN WEIGHTS FOR THE MIXTURE MODEL.
             MU - THE GAUSSIAN MEANS FOR THE MIXTURE MODEL.
             T - THE GAUSSIAN COVARIANCE MATRICES FOR THE MIXTURE
                 MODEL.
             MU0 - THE HYPERPARAMETER GIVING THE MEAN VALUE OF THE
                   GAUSSIAN PRIOR ON MU.
             U - THE HYPERPARAMETER DESCRIBING FOR THE PRIOR
                 COVARIANCE MATRIX OF THE INDIVIDUAL GAUSSIAN
                 CENTROIDS ABOUT MU0.
             W - THE HYPERPARAMETER DESCRIBING THE `TYPICAL' SCALE
                 MATRIX FOR THE PRIOR ON (T,U).
             XIMEAN - THE MEAN OF THE DISTRIBUTION FOR THE
                      INDEPENDENT VARIABLE, XI.
             XIVAR - THE STANDARD COVARIANCE MATRIX FOR THE
                     DISTRIBUTION OF THE INDEPENDENT VARIABLE, XI.
             XICORR - SAME AS XIVAR, BUT FOR THE CORRELATION MATRIX.
             CORR - THE LINEAR CORRELATION COEFFICIENT BETWEEN THE
                    DEPENDENT AND INDIVIDUAL INDEPENDENT VARIABLES,
                    XI AND ETA.
             PCORR - SAME AS CORR, BUT FOR THE PARTIAL CORRELATIONS.

 CALLED ROUTINES :

    RANDOMCHI, MRANDOMN, RANDOMWISH, RANDOMDIR, MULTINOM

 REFERENCES :

   Carroll, R.J., Roeder, K., & Wasserman, L., 1999, Flexible
     Parametric Measurement Error Models, Biometrics, 55, 44

   Kelly, B.C., 2007, Some Aspects of Measurement Error in
     Linear Regression of Astronomical Data, ApJ, In press
     (astro-ph/0705.2774)

   Gelman, A., Carlin, J.B., Stern, H.S., & Rubin, D.B., 2004,
     Bayesian Data Analysis, Chapman & Hall/CRC

(See $IDLUTILS_DIR/goddard/pro/math/mlinmix_err.pro)

MMM

 NAME:
       MMM
 PURPOSE: 
       Estimate the sky background in a stellar contaminated field.
 EXPLANATION:  
       MMM assumes that contaminated sky pixel values overwhelmingly display 
       POSITIVE departures from the true value.  Adapted from DAOPHOT 
       routine of the same name.

 CALLING SEQUENCE:
       MMM, sky, [ skymod, sigma, skew, HIGHBAD = , READNOISE=, /DEBUG, 
                  NSKY=, /INTEGER,/SILENT]

 INPUTS:
       SKY - Array or Vector containing sky values.  This version of
               MMM does not require SKY to be sorted beforehand.  SKY
               is unaltered by this program.

 OPTIONAL OUTPUTS:
       skymod - Scalar giving estimated mode of the sky values
       SIGMA -  Scalar giving standard deviation of the peak in the sky
               histogram.  If for some reason it is impossible to derive
               skymod, then SIGMA = -1.0
       SKEW -   Scalar giving skewness of the peak in the sky histogram

               If no output variables are supplied or if /DEBUG is set
               then the values of skymod, SIGMA and SKEW will be printed.

 OPTIONAL KEYWORD INPUTS:
       HIGHBAD - scalar value of the (lowest) "bad" pixel level (e.g. cosmic 
                rays or saturated pixels) If not supplied, then there is 
                assumed to be no high bad pixels.
       MINSKY - Integer giving mininum number of sky values to be used.   MMM
                will return an error if fewer sky elements are supplied.
                Default = 20.
       MAXITER - integer giving maximum number of iterations allowed,default=50
       READNOISE - Scalar giving the read noise (or minimum noise for any 
                pixel).     Normally, MMM determines the (robust) median by 
                averaging the central 20% of the sky values.     In some cases
                where the noise is low, and pixel values are quantized a
                larger fraction may be needed.    By supplying the optional
                read noise parameter, MMM is better able to adjust the
                fraction of pixels used to determine the median.                
       /INTEGER - Set this keyword if the  input SKY vector only contains
                discrete integer values.    This keyword is only needed if the
                SKY vector is of type float or double precision, but contains 
                only discrete integer values.     (Prior to July 2004, the
                equivalent of /INTEGER was set for all data types)
       /DEBUG - If this keyword is set and non-zero, then additional 
               information is displayed at the terminal.
       /SILENT - If set, then error messages will be suppressed when MMM
                cannot compute a background.    Sigma will still be set to -1
 OPTIONAL OUTPUT KEYWORD:
      NSKY - Integer scalar giving the number of pixels actually used for the
             sky computation (after outliers have been removed).
 NOTES:
       (1) Program assumes that low "bad" pixels (e.g. bad CCD columns) have
       already been deleted from the SKY vector.
       (2) MMM was updated in June 2004 to better match more recent versions
       of DAOPHOT.
       (3) Does not work well in the limit of low Poisson integer counts
       (4) MMM may fail for strongly skewed distributions.
 METHOD:
       The algorithm used by MMM consists of roughly two parts:
       (1) The average and sigma of the sky pixels is computed.   These values
       are used to eliminate outliers, i.e. values with a low probability
       given a Gaussian with specified average and sigma.   The average
       and sigma are then recomputed and the process repeated up to 20
       iterations:
       (2) The amount of contamination by stars is estimated by comparing the 
       mean and median of the remaining sky pixels.   If the mean is larger
       than the median then the true sky value is estimated by
       3*median - 2*mean
         
 REVISION HISTORY:
       Adapted to IDL from 1986 version of DAOPHOT in STSDAS, 
       W. Landsman, STX Feb 1987
       Added HIGHBAD keyword, W. Landsman January, 1991
       Fixed occasional problem with integer inputs    W. Landsman  Feb, 1994
       Avoid possible 16 bit integer overflow   W. Landsman  November 2001
       Added READNOISE, NSKY keywords,  new median computation   
                          W. Landsman   June 2004
       Added INTEGER keyword W. Landsman July 2004
       Improve numerical precision  W. Landsman  October 2004
       Fewer aborts on strange input sky histograms W. Landsman October 2005
       Added /SILENT keyword  November 2005
       Fix too many /CON keywords to MESSAGE  W.L. December 2005
       Fix bug introduced June 2004 removing outliers when READNOISE not set
         N. Cunningham/W. Landsman  January 2006
       Make sure that MESSAGE never aborts  W. Landsman   January 2008
       Add mxiter keyword and change default to 50  W. Landsman August 2011
       Added MINSKY keyword W.L. December 2011

(See $IDLUTILS_DIR/goddard/pro/idlphot/mmm.pro)

MODFITS

 NAME:
      MODFITS
 PURPOSE:
      Modify a FITS file by updating the header and/or data array.  
 EXPLANATION:
      Update the data and/or header in a specified FITS extension or primary
      HDU.
    
      The size of the supplied FITS header or data array does not
      need to match the size of the existing header or data array.

 CALLING SEQUENCE:
      MODFITS, Filename_or_fcb, Data, [ Header, EXTEN_NO =, EXTNAME= , ERRMSG=]

 INPUTS:
      FILENAME/FCB = Scalar string containing either the name of the FITS file  
                  to be modified, or the IO file control block returned after 
                  opening the file with FITS_OPEN,/UPDATE.   The explicit
                  use of FITS_OPEN can save time if many extensions in a 
                  single file will be updated.

      DATA - data array to be inserted into the FITS file.   Set DATA = 0
               to leave the data portion of the FITS file unmodified.   Data
               can also be an IDL structure (e.g. as returned by MRDFITS). 
               provided that it does not include IDL pointers.

      HEADER - FITS header (string array) to be updated in the FITS file.

 OPTIONAL INPUT KEYWORDS:
      A specific extension can be specified with either the EXTNAME or
      EXTEN_NO keyword
 
      EXTEN_NO - scalar integer specifying the FITS extension to modified.  For
               example, specify EXTEN = 1 or /EXTEN to modify the first 
               FITS extension.
      EXTNAME - string name of the extension to modify.   


 OPTIONAL OUTPUT KEYWORD:
       ERRMSG - If this keyword is supplied, then any error mesasges will be
               returned to the user in this parameter rather than depending on
               on the MESSAGE routine in IDL.   If no errors are encountered
               then a null string is returned.               

 EXAMPLES:
     (1) Modify the value of the DATE keyword in the primary header of a 
             file TEST.FITS.

              IDL> h = headfits('test.fits')      ;Read primary header
              IDL> sxaddpar,h,'DATE','2001-03-23' ;Modify value of DATE 
              IDL> modfits,'test.fits',0,h        ;Update header only

       (2) Replace the values of the primary image array in 'test.fits' with 
               their absolute values

               IDL> im = readfits('test.fits')    ;Read image array
               IDL> im = abs(im)                  ;Take absolute values
               IDL> modfits,'test.fits',im        ;Update image array

       (3) Add some HISTORY records to the FITS header in the first extension
               of a file 'test.fits'
       
               IDL> h = headfits('test.fits',/ext)  ;Read first extension hdr
               IDL> sxaddhist,['Comment 1','Comment 2'],h
               IDL> modfits,'test.fits',0,h,/ext    ;Update extension hdr

       (4) Change 'OBSDATE' keyword to 'OBS-DATE' in every extension in a 
           FITS file.    Explicitly open with FITS_OPEN to save compute time.

               fits_open,'test.fits',io,/update    ;Faster to explicity open
               for i = 1,nextend do begin          ;Loop over extensions
                   fits_read,io,0,h,/header_only,exten_no=i,/No_PDU ;Get header     
                   date= sxpar(h,'OBSDATE')         ;Save keyword value
                   sxaddpar,h,'OBS-DATE',date,after='OBSDATE' 
                   sxdelpar,h,'OBSDATE'             ;Delete bad keyword
                   modfits,io,0,h,exten_no=i        ;Update header
               endfor

           Note the use of the /No_PDU keyword in the FITS_READ call -- one 
           does *not* want to append the primary header, if the STScI 
           inheritance convention is adopted.

 NOTES:
       Uses the BLKSHIFT procedure to shift the contents of the FITS file if 
       the new data or header differs in size by more than 2880 bytes from the
       old data or header.    If a file control block (FCB) structure is 
       supplied, then the values of START_HEADER, START_DATA and NBYTES may 
       be modified if the file size changes.

       Also see the procedures FXHMODIFY to add a single FITS keyword to a 
       header in a FITS files, and FXBGROW to enlarge the size of a binary 
       table.
       
 RESTRICTIONS:
       (1) Cannot be used to modify the data in FITS files with random 
           groups or variable length binary tables.   (The headers in such
           files *can* be modified.)

       (2) If a data array but no FITS header is supplied, then MODFITS does 
           not check to make sure that the existing header is consistent with
           the new data.

       (3) Does not work with compressed files

       (4) The Checksum keywords will not be updated if the array to be 
           updated is supplied as a structure (e.g. from MRDFITS). 
 PROCEDURES USED:
       Functions:   N_BYTES(), SXPAR()
       Procedures:  BLKSHIFT, CHECK_FITS, FITS_OPEN, FITS_READ

 MODIFICATION HISTORY:
       Written,    Wayne Landsman          December, 1994
       Fixed possible problem when using WRITEU after READU   October 1997
       New and old sizes need only be the same within multiple of 2880 bytes
       Added call to IS_IEEE_BIG()     W. Landsman   May 1999
       Added ERRMSG output keyword     W. Landsman   May 2000
       Update tests for incompatible sizes   W. Landsman   December 2000
       Major rewrite to use FITS_OPEN procedures W. Landsman November 2001
       Add /No_PDU call to FITS_READ call  W. Landsman  June 2002
       Update CHECKSUM keywords if already present in header, add padding 
       if new data  size is smaller than old  W.Landsman December 2002
       Only check XTENSION value if EXTEN_NO > 1   W. Landsman Feb. 2003
       Correct for unsigned data on little endian machines W. Landsman Apr 2003
       Major rewrite to allow changing size of data or header W.L. Aug 2003
       Fixed case where updated header exactly fills boundary W.L. Feb 2004
       More robust error reporting W.L. Dec 2004
       Make sure input header ends with a END W.L.  March 2006
       Assume since V5.5, remove VMS support, assume FITS_OPEN will
           perform byte swapping   W.L. Sep 2006 
       Update FCB structure if file size changes W.L. March 2007
       Fix problem when data size must be extended W.L. August 2007
       Don't assume supplied FITS header is 80 bytes W. L. Dec 2007
       Check for new END position after adding CHECKSUM  W.L. July 2008
       Added EXTNAME input keyword  W.L. July 2008
       Allow data to be an IDL structure  A. Conley/W.L. June 2009
       Use V6.0 notation, add /NOZERO to BLKSHIFT W.L. Feb 2011
       Don't try to update Checksums when structure supplied W.L. April 2011
       Allow structure with only 1 element  W.L.  Feb 2012

(See $IDLUTILS_DIR/goddard/pro/fits/modfits.pro)

MONTH_CNV

 NAME:
       MONTH_CNV
 PURPOSE:
       Convert between a month name and  the equivalent number 
 EXPLANATION: (e.g.,
       For example, converts from 'January' to 1  or vice-versa.
 CALLING SEQUENCE:
       Result = MONTH_CNV( MonthInput, [/UP, /LOW, /SHORT ] )
 INPUTS:
       MonthInput - either a string ('January', 'Jan', 'Decem', etc.) or
               an number from 1 to 12.  Scalar or array. 
 OPTIONAL KEYWORDS:
       UP - if set and if a string is being returned, it will be in all
               uppercase letters.
       LOW - if set and if a string is being returned, it will be in all 
               lowercase letters.
       SHORT - if set and if a string is being returned, only the first
               three letters are returned.
       
 OUTPUTS:
       If the input is a string, the output is the matching month number.If
               an input string isn't a valid month name, -1 is returned.
       If the input is a number, the output is the matching month name.  The
               default format is only the first letter is capitalized.
 EXAMPLE:
       To get a vector of all the month names:
               Names = month_cnv(indgen(12)+1)

 MODIFICATION HISTORY:
       Written by:     Joel Wm. Parker, SwRI, 1998 Dec 9

(See $IDLUTILS_DIR/goddard/pro/astro/month_cnv.pro)

MOONPOS

 NAME:                                     
       MOONPOS
 PURPOSE:
       To compute the RA and Dec of the Moon at specified Julian date(s).

 CALLING SEQUENCE:
       MOONPOS, jd, ra, dec, dis, geolong, geolat, [/RADIAN ]

 INPUTS:
       JD - Julian ephemeris date, scalar or vector, double precision suggested

 OUTPUTS:
       Ra  - Apparent right ascension of the moon in DEGREES, referred to the
               true equator of the specified date(s) 
       Dec - The declination of the moon in DEGREES 
       Dis - The Earth-moon distance in kilometers (between the center of the
             Earth and the center of the Moon).
       Geolong - Apparent longitude of the moon in DEGREES, referred to the
               ecliptic of the specified date(s)
       Geolat - Apparent longitude of the moon in DEGREES, referred to the
               ecliptic of the specified date(s)

       The output variables will all have the same number of elements as the
       input Julian date vector, JD.   If JD is a scalar then the output 
       variables will be also.

 OPTIONAL INPUT KEYWORD:
       /RADIAN - If this keyword is set and non-zero, then all output variables 
               are given in Radians rather than Degrees

 EXAMPLES:
       (1) Find the position of the moon on April 12, 1992

       IDL> jdcnv,1992,4,12,0,jd    ;Get Julian date
       IDL> moonpos, jd, ra ,dec     ;Get RA and Dec of moon
       IDL> print,adstring(ra,dec,1)
               ==> 08 58 45.23  +13 46  6.1

       This is within 1" from the position given in the Astronomical Almanac
       
       (2) Plot the Earth-moon distance for every day at 0 TD in July, 1996

       IDL> jdcnv,1996,7,1,0,jd                   ;Get Julian date of July 1
       IDL> moonpos,jd+dindgen(31), ra, dec, dis  ;Position at all 31 days
       IDL> plot,indgen(31),dis, /YNOZ

 METHOD:
       Derived from the Chapront ELP2000/82 Lunar Theory (Chapront-Touze' and
       Chapront, 1983, 124, 50), as described by Jean Meeus in Chapter 47 of
       ``Astronomical Algorithms'' (Willmann-Bell, Richmond), 2nd edition, 
       1998.    Meeus quotes an approximate accuracy of 10" in longitude and
       4" in latitude, but he does not give the time range for this accuracy.

       Comparison of this IDL procedure with the example in ``Astronomical
       Algorithms'' reveals a very small discrepancy (~1 km) in the distance 
       computation, but no difference in the position calculation.

       This procedure underwent a major rewrite in June 1996, and the new
       calling sequence is *incompatible with the old* (e.g. angles now 
       returned in degrees instead of radians).

 PROCEDURES CALLED:
       CIRRANGE, ISARRAY(), NUTATE, TEN()  - from IDL Astronomy Library
       POLY() - from IDL User's Library
 MODIFICATION HISTORY:
       Written by Michael R. Greason, STX, 31 October 1988.
       Major rewrite, new (incompatible) calling sequence, much improved 
               accuracy,       W. Landsman   Hughes STX      June 1996
       Added /RADIAN keyword  W. Landsman August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Use improved expressions for L',D,M,M', and F given in 2nd edition of
            Meeus (very slight change),  W. Landsman    November 2000
       Avoid 32767 overflow   W. Landsman January 2005

(See $IDLUTILS_DIR/goddard/pro/astro/moonpos.pro)

MPHASE

 NAME:
       MPHASE
 PURPOSE:
       Return the illuminated fraction of the Moon at given Julian date(s) 

 CALLING SEQUENCE:
       MPHASE, jd, k
 INPUT:
       JD - Julian date, scalar or vector, double precision recommended
 OUTPUT:
       k - illuminated fraction of Moon's disk (0.0 < k < 1.0), same number
           of elements as jd.   k = 0 indicates a new moon, while k = 1 for
           a full moon.
 EXAMPLE:
       Plot the illuminated fraction of the moon for every day in July 
       1996 at 0 TD (~Greenwich noon).

       IDL> jdcnv, 1996, 7, 1, 0, jd         ;Get Julian date of July 1
       IDL> mphase, jd+dindgen(31), k        ;Moon phase for all 31 days
       IDL> plot, indgen(31),k               ;Plot phase vs. July day number

 METHOD:
       Algorithm from Chapter 46 of "Astronomical Algorithms" by Jean Meeus
       (Willmann-Bell, Richmond) 1991.   SUNPOS and MOONPOS are used to get
       positions of the Sun and the Moon (and the Moon distance).   The
       selenocentric elongation of the Earth from the Sun (phase angle)
       is then computed, and used to determine the illuminated fraction.
 PROCEDURES CALLED:
       MOONPOS, SUNPOS
 REVISION HISTORY:
       Written W. Landsman     Hughes STX           June 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Use /RADIAN keywords to MOONPOS, SUNPOS internally  W. Landsman Aug 2000

(See $IDLUTILS_DIR/goddard/pro/astro/mphase.pro)

MRANDOMN

  NAME:
     MRANDOMN
 PURPOSE:
 Function to draw NRAND random deviates from a multivariate normal
 distribution with zero mean and covariance matrix COVAR.
 
 AUTHOR : Brandon C. Kelly, Steward Obs., Sept. 2004

 INPUTS : 

    SEED - The random number generator seed, the default is IDL's
           default in RANDOMN()
    COVAR - The covariance matrix of the multivariate normal
            distribution.    
 OPTIONAL INPUTS :

    NRAND - The number of randomn deviates to draw. The default is
            one.
 OUTPUT :

    The random deviates, an [NRAND, NP] array where NP is the
    dimension of the covariance matrix, i.e., the number of
    parameters.

 ROUTINES CALLED :

    POSITIVE, DIAG

(See $IDLUTILS_DIR/goddard/pro/math/mrandomn.pro)

MRDFITS

 NAME:
     MRDFITS

 PURPOSE:
     Read all standard FITS data types into arrays or structures.

 EXPLANATION:
      Further information on MRDFITS is available at
      http://idlastro.gsfc.nasa.gov/mrdfits.html 

      **This version requires a post March 2009 version of fxposit.pro**
 CALLING SEQUENCE:
      Result = MRDFITS( Filename/FileUnit,[Exten_no/Exten_name, Header],
                       /FPACK, /NO_FPACK, /FSCALE , /DSCALE , /UNSIGNED,
                       ALIAS=strarr[2,n], /USE_COLNUM,
                       /NO_TDIM, ROWS = [a,b,...], $
                       /POINTER_VAR, /FIXED_VAR, EXTNUM= 
                       RANGE=[a,b], COLUMNS=[a,b,...]), ERROR_ACTION=x,
                       COMPRESS=comp_prog, STATUS=status, /VERSION, 
                       /EMPTYSTRING )

 INPUTS:
      Filename = String containing the name of the file to be read or
                 file number of an open unit.  If an empty string is supplied,
                 then user will be prompted for the file name.    The user
                 will also be prompted if a wild card is given in the file
                 name, and there is more than one file name match.
                 If the file name ends in .gz or .fz (or .Z on Unix systems)
                 the file will be dynamically decompressed.
                                    or
      FiluUnit = An integer file unit which has already been
                 opened for input.  Data will be read from this
                 unit and the unit will be left pointing immediately
                 after the HDU that is read.  Thus to read a compressed
                 file with many HDU's a user might do something like:
                      lun=fxposit(filename, 3)  ; Skip the first three HDU's
                      repeat begin
                          thisHDU = mrdfits(lun, 0, hdr, status=status)
                          ... process the HDU ...
                      endrep until status lt 0

      Exten_no= Extension number to be read, 0 for primary array.
                 Assumed 0 if not specified.
                 If a unit rather than a filename
                 is specified in the first argument, this is
                 the number of HDU's to skip from the current position.
      Exten_name - Name of the extension to read (as stored in the EXTNAME
                 keyword).   This is a slightly slower method then specifying
                 the extension number.
 OUTPUTS:
      Result = FITS data array or structure constructed from
               the designated extension.  The format of result depends
               upon the type of FITS data read.
             Non-group primary array or IMAGE extension:
               A simple multidimensional array is returned with the
               dimensions given in the NAXISn keywords.
             Grouped image data with PCOUNT=0.
               As above but with GCOUNT treated as NAXIS(n+1).
             Grouped image data with PCOUNT>0.
               The data is returned as an array of structures.  Each
               structure has two elements.  The first is a one-dimensional
               array of the group parameters, the second is a multidimensional
               array as given by the NAXIS2-n keywords.
             ASCII and BINARY tables.
               The data is returned as a structure with one column for
               each field in the table.  The names of the columns are
               normally taken from the TTYPE keywords (but see USE_COLNUM).
               Bit field columns
               are stored in byte arrays of the minimum necessary
               length.  Spaces and invalid characters are replaced by 
               underscores, and other invalid tag names are converted using
               the IDL_VALIDNAME(/CONVERT_ALL) function.
               Columns specified as variable length columns are stored
               with a dimension equal to the largest actual dimension
               used.  Extra values in rows are filled with 0's or blanks.
               If the size of the variable length column is not
               a constant, then an additional column is created giving the 
               size used in the current row.  This additional column will 
               have a tag name of the form L#_"colname" where # is the column
               number and colname is the column name of the variable length
               column.   If the length of each element of a variable length 
               column is 0 then the column is deleted.


 OPTIONAL OUTPUT:
       Header = String array containing the header from the FITS extension.

 OPTIONAL INPUT KEYWORDS:
       ALIAS    The keyword allows the user to specify the column names
                to be created when reading FITS data.  The value of
                this keyword should be a 2xn string array.  The first
                value of each pair of strings should be the desired
                tag name for the IDL column.  The second should be
                the FITS TTYPE value.  Note that there are restrictions
                on valid tag names.  The order of the ALIAS keyword
                is compatible with MWRFITS.
       COLUMNS - This keyword allows the user to specify that only a
                subset of columns is to be returned.  The columns
                may be specified either as number 1,... n or by
                name or some combination of these two.
                If /USE_COLNUM is specified names should be C1,...Cn.
                The use of this keyword will not save time or internal
                memory since the extraction of specified columns
                is done after all columns have been retrieved from the
                FITS file.      Structure columns are returned in the order
                supplied in this keyword.
       COMPRESS - This keyword allows the user to specify a
                decompression program to use to decompress a file that
                will not be automatically recognized based upon
                the file name.
       /DSCALE - As with FSCALE except that the resulting data is
                stored in doubles.
       /EMPTYSTRING - There was a bug in memory management for IDL versions 
                 prior to V8.0, causing a memory leak when reading
                 empty strings in a FITS table.   Setting /EMPTYSTRING will
                 avoid this problem by first reading strings into bytes and
                 then converting.   However, there is a performance penalty.                 
       ERROR_ACTION - Set the on_error action to this value (defaults
                to 2).
       /FIXED_VAR- Translate variable length columns into fixed length columns
                and provide a length column for truly varying columns.
                This was only behavior prior to V2.5 for MRDFITS and remains
                the default (see /POINTER_VAR)
       /FPACK - If set, then assume the FITS file uses FPACK compression 
                (http://heasarc.gsfc.nasa.gov/fitsio/fpack/).     MRDFITS
                will automatically detect FPACK compressed files, but it is
                more efficient to supply the /FPACK keyword.   A file with an
                extension of .fz is assumed to be Fpack compressed.
       /NO_FPACK - If present, then MRDFITS will not uncompress an extension
                compressed with FPACK, but will just read the compressed
                binary stream. 
       /FSCALE - If present and non-zero then scale data to float
                numbers for arrays and columns which have either
                non-zero offset or non-unity scale.
                If scaling parameters are applied, then the corresponding
                FITS scaling keywords will be modified.
       NO_TDIM  - Disable processing of TDIM keywords.  If NO_TDIM
                is specified MRDFITS will ignore TDIM keywords in
                binary tables.
       /POINTER_VAR- Use pointer arrays for variable length columns.
                In addition to changing the format in which
                variable length arrays are stored, if the pointer_var
                keyword is set to any value other than 1 this also disables
                the deletion of variable length columns. (See /FIXED_VAR)
                Note that because pointers may be present in the output
                structure, the user is responsible for memory management
                when deleting or reassigning the structure (e.g. use HEAP_FREE
                first).
       RANGE  - A scalar or two element vector giving the start
                and end rows to be retrieved.  For ASCII and BINARY
                tables this specifies the row number.  For GROUPed data
                this will specify the groups.  For array images, this
                refers to the last non-unity index in the array.  E.g.,
                for a 3 D image with NAXIS* values = [100,100,1], the
                range may be specified as 0:99, since the last axis
                is suppressed.  Note that the range uses IDL indexing
                So that the first row is row 0.
                If only a single value, x, is given in the range,
                the range is assumed to be [0,x-1].
       ROWS -  A scalar or vector specifying a  specific row or rows to read 
               (first row is 0).   For example to read rows 0,
               12 and 23 only, set ROWS=[0,12,23].   Valid for images, ASCII 
               and binary tables, but not GROUPed data.   For images
               the row numbers refer to the last non-unity index in the array.
               Note that the use of the ROWS will not improve the speed of
               MRDFITS since the entire table will be read in, and then subset
               to the specified rows.     Cannot be used at the same time as 
               the RANGE keyword
       /SILENT - Suppress informative messages.
       STRUCTYP - The structyp keyword specifies the name to be used
                for the structure defined when reading ASCII or binary
                tables.  Generally users will not be able to conveniently
                combine data from multiple files unless the STRUCTYP
                parameter is specified.  An error will occur if the
                user specifies the same value for the STRUCTYP keyword
                in calls to MRDFITS in the same IDL session for extensions
                which have different structures.
       /UNSIGNED - For integer data with appropriate zero points and scales
                read the data into unsigned integer arrays.
       /USE_COLNUM - When creating column names for binary and ASCII tables
                MRDFITS attempts to use the appropriate TTYPE keyword
                values.  If USE_COLNUM is specified and non-zero then
                column names will be generated as 'C1, C2, ... 'Cn'
                for the number of columns in the table.
       /VERSION Print the current version number

 OPTIONAL OUTPUT KEYWORDS:
       EXTNUM - the number of the extension actually read.   Useful if the
                 user specified the extension by name.
       OUTALIAS - This is a 2xn string array where the first column gives the
                actual structure tagname, and the second gives the
                corresponding FITS keyword name (e.g. in the TTYPE keyword).   
                This array can be passed directly to
                the alias keyword of MWRFITS to recreate the file originally
                read by MRDFITS.
       STATUS - A integer status indicating success or failure of
                the request.  A status of >=0 indicates a successful read.
                Currently
                    0 -> successful completion
                   -1 -> error
                   -2 -> end of file

 EXAMPLES:
       (1) Read a FITS primary array:
               a = mrdfits('TEST.FITS')    or
               a = mrdfits('TEST.FITS', 0, header)
       The second example also retrieves header information.

       (2) Read rows 10-100 of the second extension of a FITS file.
               a = mrdfits('TEST.FITS', 2, header, range=[10,100])

       (3) Read a table and ask that any scalings be applied and the
       scaled data be converted to doubles.  Use simple column names,
       suppress outputs.
               a = mrdfits('TEST.FITS', 1, /dscale, /use_colnum, /silent)

       (4) Read rows 3, 34 and 52 of a binary table and request that 
           variable length columns be stored as a pointer variable in the 
           output structure
              a = mrdfits('TEST.FITS',1,rows=[3,34,52],/POINTER)
 
 RESTRICTIONS:
       (1)     Cannot handle data in non-standard FITS formats.
       (2)     Doesn't do anything with BLANK or NULL values or
               NaN's.  They are just read in.  They may be scaled
               if scaling is applied.
 NOTES:
       This multiple format FITS reader is designed to provide a
       single, simple interface to reading all common types of FITS data.
       MRDFITS DOES NOT scale data by default.  The FSCALE or DSCALE
       parameters must be used.

       Null values in an FITS ASCII table are converted to NaN (floating data),
       or -2147483647L (longwords) or '...' (strings).   

 PROCEDURES USED:
       The following procedures are contained in the main MRDFITS program.
           MRD_IMAGE           -- Generate array/structure for images.
           MRD_READ_IMAGE      -- Read image data.
           MRD_ASCII           -- Generate structure for ASCII tables.
           MRD_READ_ASCII      -- Read an ASCII table.
           MRD_TABLE           -- Generate structure for Binary tables.
           MRD_READ_TABLE      -- Read binary table info.
           MRD_READ_HEAP       -- Read variable length record info.
           MRD_SCALE           -- Apply scaling to data.
           MRD_COLUMNS         -- Extract columns.

        Other ASTRON Library routines used
           FXPAR(), FXADDPAR, FXPOSIT, FXMOVE(), MATCH, MRD_STRUCT(), MRD_SKIP 

 MODIfICATION HISTORY:
       V1.0 November 9, 1994 ----  Initial release.
          Creator: Thomas A. McGlynn
       V1.1 January 20, 1995 T.A. McGlynn
          Fixed bug in variable length records.
          Added TDIM support -- new routine mrd_tdim in MRD_TABLE.
       V1.2
          Added support for dynamic decompression of files.
          Fixed further bugs in variable length record handling.
       V1.2a
          Added NO_TDIM keyword to turn off TDIM processing for
          those who don't want it.
          Bug fixes: Handle one row tables correctly, use BZERO rather than
               BOFFSET.     Fix error in scaling of images.  
       V1.2b 
          Changed MRD_HREAD to handle null characters in headers.
       V2.0 April 1, 1996
          -Handles FITS tables with an arbitrary number of columns.
          -Substantial changes to MRD_STRUCT to allow the use of
          substructures when more than 127 columns are desired.
          -All references to table columns are now made through the
          functions MRD_GETC and MRD_PUTC.  See description above.
          -Use of SILENT will now eliminate compilation messages for
          temporary functions.
          -Bugs in handling of variable length columns with either
          a single row in the table or a maximum of a single element
          in the column fixed.
          -Added support for DCOMPLEX numbers in binary tables (M formats) for
          IDL versions above 4.0.  
          -Created regression test procedure to check in new versions.
          -Added error_action parameter to allow user to specify
          on_error action.  This should allow better interaction with
          new CHECK facility.  ON_ERROR statements deleted from
          most called routines.
          - Modified MRDFITS to read in headers containing null characters
          with a warning message printed.
       V2.0a April 16, 1996
          - Added IS_IEEE_BIG() checks (and routine) so that we don't
          worry about IEEE to host conversions if the machine's native
          format is IEEE Big-endian.
       V2.1 August 24, 1996
          - Use resolve_routine for dynamically defined functions
          for versions > 4.0
          - Fix some processing in random groups format.
          - Handle cases where the data segment is--legally--null.
          In this case MRDFITS returns a scalar 0.
          - Fix bugs with the values for BSCALE and BZERO (and PSCAL and
          PZERO) parameters set by MRDFITS.
       V2.1a April 24, 1997  Handle binary tables with zero length columns
       V2.1b May 13,1997 Remove whitespace from replicate structure definition
       V2.1c May 28,1997 Less strict parsing of XTENSION keyword
       V2.1d June 16, 1997 Fixed problem for >32767 entries introduced 24-Apr
       V2.1e Aug 12, 1997 Fixed problem handling double complex arrays
       V2.1f Oct 22, 1997 IDL reserved words can't be structure tag names
       V2.1g Nov 24, 1997 Handle XTENSION keywords with extra blanks.
       V2.1h Jul 26, 1998 More flexible parsing of TFORM characters
       V2.2 Dec 14, 1998 Allow fields with longer names for
                        later versions of IDL.
                        Fix handling of arrays in scaling routines.
                        Allow >128 fields in structures for IDL >4.0
                        Use more efficient structure copying for
                        IDL>5.0
       V2.2b June 17, 1999 Fix bug in handling case where
                           all variable length columns are deleted
                           because they are empty.
       V2.3 March 7, 2000 Allow user to supply file handle rather
                          than file name.
                          Added status field.
                          Now needs FXMOVE routine
       V2.3b April 4, 2000
                          Added compress option (from D. Palmer)
       V2.4  July 4, 2000 Added STATUS=-1 for "File access error" (Zarro/GSFC)
       V2.4a May 2, 2001  Trim binary format string   (W. Landsman)
       V2.5 December 5, 2001 Add unsigned, alias, 64 bit integers. version, $
                           /pointer_val, /fixed_var.
       V2.5a Fix problem when both the first and the last character
            in a TTYPEnn value are invalid structure tag characters
       V2.6 February 15, 2002 Fix error in handling unsigned numbers, $
                           and 64 bit unsigneds. (Thanks to Stephane Beland)
       V2.6a September 2, 2002 Fix possible conflicting data structure for
                          variable length arrays (W. Landsman)
       V2.7 July, 2003  Added Rows keyword (W. Landsman)
       V2.7a September  2003 Convert dimensions to long64 to handle huge files
       V2.8 October 2003 Use IDL_VALIDNAME() function to ensure valid tag names
                         Removed OLD_STRUCT and TEMPDIR keywords W. Landsman
       V2.9 February 2004 Added internal MRD_FXPAR procedure for faster
                     processing of binary table headers E. Sheldon
       V2.9a March 2004 Restore ability to read empty binary table W. Landsman
             Swallow binary tables with more columns than given in TFIELDS
       V2.9b Fix to ensure order of TFORMn doesn't matter
       V2.9c Check if extra degenerate NAXISn keyword are present W.L. Oct 2004 
       V2.9d Propagate /SILENT to MRD_HREAD, more LONG64 casting W. L. Dec 2004
       V2.9e Add typarr[good] to fix a problem reading zero-length columns
             A.Csillaghy, csillag@ssl.berkeley.edu (RHESSI)
       V2.9f Fix problem with string variable binary tables, possible math 
             overflow on non-IEEE machines  WL Feb. 2005 
       V2.9g Fix problem when setting /USE_COLNUM   WL Feb. 2005
       V2.10 Use faster keywords to BYTEORDER  WL May 2006
       V2.11  Add ON_IOERROR, CATCH, and STATUS keyword to MRD_READ_IMAGE to
             trap EOF in compressed files DZ  Also fix handling of unsigned 
             images when BSCALE not present  K Chu/WL   June 2006 
       V2.12 Allow extension to be specified by name, added EXTNUM keyword
                     WL    December 2006
       V2.12a Convert ASCII table column to DOUBLE if single precision is
                 insufficient  
       V2.12b Fixed problem when both /fscale and /unsigned are set 
                  C. Markwardt    Aug 2007
       V2.13  Use SWAP_ENDIAN_INPLACE instead of IEEE_TO_HOST and IS_IEEE_BIG
                W. Landsman Nov 2007
       V2.13a One element vector allowed for file name W.L. Dec 2007
       V2.13b More informative error message when EOF found W.L. Jun 2008
       V2.14  Use vector form of VALID_NUM(), added OUTALIAS keyword
                                       W.L. Aug 2008
       V2.15  Use new FXPOSIT which uses on-the-fly byteswapping W.L. Mar 2009
       V2.15a Small efficiency updates to MRD_SCALE W.L. Apr 2009
       V2.15b Fixed typo introduced Apr 2009
       V2.15c Fix bug introduced Mar 2009  when file unit used W.L. July 2009
       V2.16  Handle FPACK compressed files    W. L. July 2009
       V2.17  Use compile_opt hidden on all routines except mrdfits.pro W.L. July 2009
       V2.18  Added /EMPTYSTRING keyword W. Landsman August 2009
       V2.18a Fix Columns keyword output, A. Kimball/ W. Landsman Feb 2010
       V2.18b Fix bug with /EMPTYSTRING and multidimensional strings
                             S. Baldridge/W.L. August 2010
       V2.18c Fix unsigned bug caused by compile_opt idl2 WL  Nov 2010
       V2.19  Use V6.0 operators WL Nov 2010
       V2.19a Fix complex data conversion in variable length tables WL Dec 2010 
       V2.19b Fix bug with /FSCALE introduced Nov 2010 WL Jan 2011
       V2.19c Fix bug with ROWS keyword introduced Nov 2010 WL Mar 2011
       V2.20  Convert Nulls in ASCII tables, better check of duplicate keywords
                                            WL May 2011

(See $IDLUTILS_DIR/goddard/pro/fits/mrdfits.pro)

MRD_HREAD

 NAME: 
     MRD_HREAD

 PURPOSE: 
     Reads a FITS header from an opened disk file or Unix pipe
 EXPLANATION:
     Like FXHREAD but also works with compressed Unix files

 CALLING SEQUENCE: 
     MRD_HREAD, UNIT, HEADER  [, STATUS, /SILENT, ERRMSG =, /FIRSTBLOCK ]
 INPUTS: 
     UNIT    = Logical unit number of an open FITS file
 OUTPUTS: 
     HEADER  = String array containing the FITS header.
 OPT. OUTPUTS: 
     STATUS  = Condition code giving the status of the read.  Normally, this
                 is zero, but is set to -1 if an error occurs, or if the
                 first byte of the header is zero (ASCII null).
 OPTIONAL KEYWORD INPUT:
      /FIRSTBLOCK - If set, then only the first block (36 lines or less) of 
                the FITS header are read into the output variable.   If only
                size information (e.g. BITPIX, NAXIS) is needed from the
                header, then the use of this keyword can save time.  The 
                file pointer is still positioned at the end of the header,
                even if the /FIRSTBLOCK keyword is supplied.
      /SILENT - If set, then warning messages about any invalid characters in
                the header are suppressed.
      /SKIPDATA - If set, then the file point is positioned at the end of the
                HDU after the header is read, i.e. the following data block
                is skipped.   Useful, when one wants to the read the headers
                of multiple extensions.
      /NO_BADHEADER - if set, returns if FITS header has illegal characters
                By default, MRD_HREAD replaces bad characters with blanks,
                issues a warning, and continues.
 OPTIONAL OUTPUT PARAMETER:
       ERRMSG  = If this keyword is present, then any error messages will be
                 returned to the user in this parameter rather than
                 depending on the MESSAGE routine in IDL.  If no errors are
                 encountered, then a null string is returned.
 RESTRICTIONS: 
      The file must already be positioned at the start of the header.  It
      must be a proper FITS file.
 SIDE EFFECTS: 
       The file ends by being positioned at the end of the FITS header, unless
       an error occurs.
 REVISION HISTORY:
      Written,  Thomas McGlynn                     August 1995
      Modified, Thomas McGlynn		     January 1996
         Changed MRD_HREAD to handle Headers which have null characters
          A warning message is printed out but the program continues.
          Previously MRD_HREAD would fail if the null characters were
          not in the last 2880 byte block of the header.  Note that
          such characters are illegal in the header but frequently
          are produced by poor FITS writers.
      Added /SILENT keyword   W. Landsman   December 2000
      Added /FIRSTBLOCK keyword  W. Landsman   February 2003
      Added ERRMSG, SKIPDATA keyword W. Landsman          April 2009
      Close file unit even after error message   W.L.  October 2010
      Added /NO_BADHEADER  Zarro (ADNET), January 2012

(See $IDLUTILS_DIR/goddard/pro/fits/mrd_hread.pro)

MRD_SKIP

 NAME:
       MRD_SKIP
 PURPOSE:
       Skip a number of bytes from the current location in a file or a pipe
 EXPLANATION:
       First tries using POINT_LUN and if this doesn't work, perhaps because
       the unit is a pipe or a socket, MRD_SKIP will just read in the 
       requisite number  of bytes.    
 CALLING SEQUENCE:
       MRD_SKIP, Unit, Nskip

 INPUTS:
       Unit - File unit for the file or pipe in question, integer scalar
       Nskip - Number of bytes to be skipped, positive integer
 NOTES:
       This routine should be used in place of POINT_LUN wherever a pipe
       or socket may be the input unit (see the procedure FXPOSIT for an 
       example).   Note that it assumes that it can only work with nskip >= 0 
       so it doesn't even try for negative values.      

       For reading a pipe, MRD_SKIP currently uses a maximum buffer size
       of 8 MB.   This chunk value can be increased for improved efficiency
       (or decreased if you really have little memory.)
 REVISION HISTORY:
       Written, Thomas A. McGlynn    July 1995
	Don't even try to skip bytes on a pipe with POINT_LUN, since this
	might reset the current pointer     W. Landsman        April 1996
       Increase buffer size, check fstat.compress W. Landsman  Jan 2001
       Only a warning if trying read past EOF   W. Landsman   Sep 2001
       Use 64bit longword for skipping in very large files W. Landsman Sep 2003
       Assume since V5.4, fstat.compress available W. Landsman April 2006
       POINT_LUN for compressed files is as fast as any W. Landsman Oct 2006
       Don't try to use POINT_LUN on compressed files W. Landsman Dec. 2006

(See $IDLUTILS_DIR/goddard/pro/misc/mrd_skip.pro)

MRD_STRUCT

 NAME:
       MRD_STRUCT
 PURPOSE:
       Return a structure as defined in the names and values data.
 CALLING SEQUENCE:
       struct = MRD_STRUCT(NAMES, VALUES, NROW, STRUCTYP='name' )
 INPUT PARAMETERS:
       NAMES   = A string array of names of structure fields.
       VALUES  = A string array giving the values of the structure
                 fields.  See examples below.
       NROW    = The number of elements in the structure array.
       
 RETURNS:
       A structure as described in the parameters or 0 if an error
       is detected.

 OPTIONAL KEYWORD PARAMETERS:
       /NO_EXECUTE - If set then the use of the EXECUTE() statement is avoided.
                  By default, the NO_EXECUTE pathway is used if IDL is 
                  running under the Virtual Machine.    Note if  /NO_EXECUTE
                  is set, then the user cannot supply arbitary values, but
                  all possible values used by MRDFITS will be allowed.
       STRUCTYP = The structure type.  Since IDL does not allow the
                  redefinition of a named structure it is an error
                  to call MRD_STRUCT with different parameters but
                  the same STRUCTYP in the same session.  If this
                  keyword is not set an anonymous structure is created.
 COMMON BLOCKS:
       MRD_COMMON
 SIDE EFFECTS:                                                            
       May create a temporary file if the structure definition is too long 
       for the EXECUTE function and using old style structures

 RESTRICTIONS:
       By default, the program defines the structure in a long string
       which is executed with CREATE_STRUCT within a single EXECUTE statement.

       If program is being run in the IDL Virtual machine (EXECUTE statement
       not allowed), then a separate CREATE_STRUCT statement is called
       for each tag.   This mode does not have the full capabilities of the
       normal mode, but should be sufficient for use with MRDFITS().
 PROCEDURE:
       A structure definition is created using the parameter values.
       MRD_NSTRUCT is called  and generates the structure in pieces using the
       execute and create_struct keywords.

 EXAMPLES:
       (1) str = mrd_struct(['fld1', 'fld2'], ['0','dblarr(10,10)'],3)
           print, str(0).fld2(3,3)
       Note that "0" is always considered short integer even if the default
       integer is set to long.
          

       (2) str = mrd_struct(['a','b','c','d'],['1', '1.', '1.d0', "'1'"],1)
               ; returns a structure with integer, float, double and string
               ; fields.
 PROCEDURE CALLS:
       GETTOK() - needed for virtual machine mode only
 MODIFICATION HISTORY:
       Created by T. McGlynn October, 1994.
       Modified by T. McGlynn September, 1995.
          Added capability to create substructures so that structure
          may contain up to 4096 distinct elements.  [This can be
          increased by futher iteration of the process used if needed.]
       Removed V4.0 reference to common block  October 1997
       Allowed unlimited number of structure elements if the version
       is greater than 5.0.  Put back in code to handle prior versions.
       The [] will need to be translated back to () for this to
       work.  T. McGlynn December 15 1998.
       Add MRD_NSTRUCT since IDL has mysterious problems compiling
       very large structures.
       Removed TEMPDIR and OLD_STRUCT keywords  W. Landsman October 2003   
       Alternate pathway without EXECUTE for V6.0 virtual machine, D. Lindler
       Removed limit on EXECUTE statement.  W. Landsman  October 2003
       Restore EXECUTE limit (sigh...), added NO_EXECUTE keyword
                         W. Landsman July 2004
       Fix use of STRUCTYP with /NO_EXECUTE  W. Landsman June 2005
       Assume since V6.0 (lmgr function available), remove 131 string length
             limit for execute    W. Landsman Jun 2009 
       Restore EXECUTE limit (sigh...)   W. Landsman July 2009 
       Make sure "0" is a short integer even with compile_opt idl2  July 2010
       Added "0.0", "0.0d", "0u", "0ul", and "0ull" as valid tags
             for /NO_EXECUTE  E. Rykoff May 2012

(See $IDLUTILS_DIR/goddard/pro/structure/mrd_struct.pro)

MULTINOM

 NAME:
   MULTINOM
 PURPOSE:
 SIMULATE MULTINOMIAL RANDOM VARIABLES

 AUTHOR : BRANDON C. KELLY, STEWARD OBS., APR 2006

 INPUTS :

   N - THE NUMBER OF TRIALS
   P - A K-ELEMENT VECTOR CONTAINING THE PROBABILITIES FOR EACH
       CLASS.

 OPTIONAL INPUTS :

   NRAND - THE NUMBER OF RANDOM VARIABLES TO DRAW
   SEED - THE SEED FOR THE RANDOM NUMBER GENERATOR

 OUTPUT :
   NRAND RANDOM DRAWS FROM A MULTINOMIAL DISTRIBUTION WITH PARAMETERS
   N AND P.

(See $IDLUTILS_DIR/goddard/pro/math/multinom.pro)

MULTIPLOT

 Name:
   MULTIPLOT

 Purpose:
	Create multiple plots with simple control over the gaps between plots.
   By default, the gap is zero but this can be set with the
   gap= keyword, or xgap=, ygap= for individual control over different axes.
   You can also place a single title along the x, y and top axes of the
   matrix of plots using the mtitle, mxtitle and mytitle keywords.

	It is good for data with one or two shared axes and retains all the
	versatility of the plot commands (e.g. all keywords and log scaling).
	The plots are connected with the shared axes, which saves space by
	omitting redundant ticklabels and titles.  Multiplot does this by
	setting !p.position, !x.tickname and !y.tickname automatically.
	A call (multiplot,/reset) restores original values.

 CALLING SEQUENCE:
	multiplot, pmulti, 
       gap=, xgap=, ygap=, 
       /square, 
       /doxaxis, /doyaxis, 
       mTitle=, mTitSize=, mTitOffset=, 
       mxTitle=, mxTitSize=, mxTitOffset=, 
       myTitle=, myTitSize=, myTitOffset=, 
       xtickformat=, ytickformat=
       /default, /reset, /rowmajor, /initialize

 INPUTS:
   pmulti: Optional input. [Nx,Ny] array describing the shape of the
       matrix of plots.  This is equivalent to the 2nd and 3rd elements
       of !p.multi.  Or you can send all 5 elements of the !p.multi.

 KEYWORD INPUTS:
   gap=: Set the gap between plots in normalized units.  Default is 0.
       This input overrides the xgap and ygap inputs.
   xgap=: Gap between plots in the x direction. Default 0. To set both
       x and y gap to the same value just use the gap keyword.
   ygap=: Gap between plots in the y direction. Default 0. To set both
       x and y gap to the same value just use the gap keyword.

   mTitle: A single title to go across the top of the matrix of plots,
       as opposed to the plot over single plots you generate with the
       plot command for example. 
   mTitSize: The font size of the top title. Default is 1.25*!p.charsize
   mTitOffset: Offset of the title in the y-direction.
   mxTitle, mxTitSize, mxTitOffset: same as above but for the x-axis title
   myTitle, myTitSize, myTitOffset: same as above but for the y-axis title

   xtickformat, ytickformat: Set the default tick formats when the ticks
       are plotted. This allows the user to avoid sending this to each
       plotting command which can have unexpected results if that axis
       was not to get tick labels in a given point in the matrix.

 KEYWORDS SWITCHES:
   /square: Force the axis ratio of each plot to be square. Note if
       xgap and ygap are set to different values, this axis ratio will
       not be preserved.  It will be preserved if gap= is used.

   /doxaxis: Put axis labels, etc on the axis. Default is to place labels
       only on the left side and bottom sides of the plot matrix, but may
       be useful when some cells are empty; for example the x-axis of
       a 2x2 grid when only 3 total plots will be created.
   /doyaxis: Put axis labels, etc on the yxis.  Default is to place labels
       only on the left side and bottom sides of the plot matrix, but may
       be useful when some cells are empty; for example the x-axis of
       a 2x2 grid when only 3 total plots will be created.

   /rowmajor: Like setting 5th element of !p.multi to 1. 
   /reset: Set plotting parameters to their saved values from before
       multiplot was initially called.
   /default: Set plotting parameters to IDL defaults.  This is useful
       when the saved parameters get in a whacky state.
   /initialize: Just do the initialization. This is what happends when
       you first call multiplot anyway.

 EXAMPLES:
   ; Make an array of plots [4,3] with a gap of 0.1 (in norm. coords.)
   ; and overall titles along the x and y axes as given.  Force the
   ; plots to be square.

       cgerase & multiplot, [4,3], /square, gap=0.1, mXtitle='R', mYtitle='F(R)'
       for i=0,4*3-1 do begin
           cgplot, struct[i].x, struct[i].y, psym=4
           multiplot
       endfor
       multiplot,/reset

 Side Effects:
   Multiplot sets a number of system variables: !p.position, !p.multi,
	!x.tickname, !y.tickname, !P.noerase---but all can be reset with
	the call: multiplot,/reset  

   Things can get out of wack if your program crashes in the middle of 
   making a matrix of plots, and often /reset will not fix it.  In those 
   cases, calling multiplot,/default will often fix the problem.

 Restrictions:
	1. If you use !p.multi as the method of telling how many plots
	are present, you have to set !p.multi at the beginning each time you
	use multiplot or call multiplot with the /reset keyword.
	2. There is no way to make plots of different sizes; each plot
	covers the same area on the screen or paper.

 Modification history:
	write, 21-23 Mar 94, Fred Knight (knight@ll.mit.edu)
	alter plot command that sets !x.window, etc. per suggestion of
	  Mark Hadfield (hadfield@storm.greta.cri.nz), 7 Apr 94, FKK
	add a /default keyword restore IDL's default values of system vars,
	  7 Apr 94, FKK
	modify two more sys vars !x(y).tickformat to suppress user-formatted
	  ticknames, per suggestion of Mark Hadfield (qv), 8 Apr 94, FKK
       
   2001-03-20    Added /square keyword
       Work in device coordinates so we can force aspect ratio to be square 
       if requested. Erin Scott Sheldon UMichigan
       
   2007-06-18
       Can now place titles on the overall x and y axes, as well as a 
       top title using these new keywords. 
           mTitle=, mTitSize=, mTitOffset=, 
           mxTitle=, mxTitSize=, mxTitOffset=, 
           myTitle=, myTitSize=, myTitOffset=, 
       Can also control overall tick formats. Useful because can just call
       multiplot initially and set this, while calling on each call to
       the plotting program will have unexpected results if the ticks
       are not to be labelled for that place in the matrix.
           xtickformat, ytickformat
       Erin Sheldon, NYU
   2007-08-28:
       Can now add gaps between the plots with these keywords:
           gap=, xgap=, ygap=
       where the values are in normalized coordinates. Erin Sheldon, NYU
   2009-11-23
       Initialize common block if M[X/Y]TITLE set W. Landsman 
   2011-02-07
        Use Coyote Graphics  W. Landsman    
   2012-03-21
        Use cgplot on initial call to get right background  W.L.

(See $IDLUTILS_DIR/goddard/pro/plot/multiplot.pro)

MWRFITS

 NAME:
       MWRFITS
 PURPOSE:
       Write all standard FITS data types from input arrays or structures.

 EXPLANATION:
       Must be used with a post-October 2009 version of FXADDPAR.

 CALLING SEQUENCE:
       MWRFITS, Input, Filename, [Header],
                       /LSCALE , /ISCALE, /BSCALE, 
                       /USE_COLNUM, /Silent, /Create, /No_comment, /Version, $
                       Alias=, /ASCII, Separator=, Terminator=, Null=,
                       /Logical_cols, /Bit_cols, /Nbit_cols, 
                       Group=, Pscale=, Pzero=, Status=

 INPUTS:
       Input = Array or structure to be written to FITS file.

               -When writing FITS primary data or image extensions
                input should be an array.
               --If data is to be grouped
                 the Group keyword should be specified to point to
                 a two dimensional array.  The first dimension of the
                 Group array will be PCOUNT while the second dimension
                 should be the same as the last dimension of Input.
               --If Input is undefined, then a dummy primary dataset
                 or Image extension is created [This might be done, e.g.,
                 to put appropriate keywords in a dummy primary
                 HDU].

               -When writing an ASCII table extension, Input should
                be a structure array where no element of the structure
                is a structure or array (except see below).
               --A byte array will be written as A field.  No checking
                 is done to ensure that the values in the byte field
                 are valid ASCII.
               --Complex numbers are written to two columns with '_R' and
                 '_I' appended to the TTYPE fields (if present).  The
                 complex number is enclosed in square brackets in the output.
               --Strings are written to fields with the length adjusted
                 to accommodate the largest string.  Shorter strings are
                 blank padded to the right.

               -When writing a binary table extension, the input should
                be a structure array with no element of the structure
                being a substructure.

               If a structure is specified on input and the output
               file does not exist or the /CREATE keyword is specified
               a dummy primary HDU is created.

       Filename = String containing the name of the file to be written.
                By default MWRFITS appends a new extension to existing
                files which are assumed to be valid FITS.  The /CREATE
                keyword can be used to ensure that a new FITS file
                is created even if the file already exists.

 OUTPUTS:

 OPTIONAL INPUTS:
       Header = Header should be a string array.  Each element of the
                array is added as a row in the FITS  header.  No
                parsing is done of this data.  MWRFITS will prepend
                required structural (and, if specified, scaling)
                keywords before the rows specified in Header.
                Rows describing columns in the table will be appended
                to the contents of Header.
                Header lines will be extended or truncated to
                80 characters as necessary.
                If Header is specified then on return Header will have
                the header generated for the specified extension.

 OPTIONAL INPUT KEYWORDS:
       ALias=   Set up aliases to convert from the IDL structure
                to the FITS column name.  The value should be
                a STRARR(2,*) value where the first element of
                each pair of values corresponds to a column
                in the structure and the second is the name
                to be used in the FITS file.
                The order of the alias keyword is compatible with
                use in MRDFITS.
       ASCII  - Creates an ASCII table rather than a binary table.
                This keyword may be specified as:
                /ASCII - Use default formats for columns.
                ASCII='format_string' allows the user to specify
                  the format of various data types such using the following
                  syntax 'column_type:format, column_type:format'.  E.g.,
                ASCII='A:A1,I:I6,L:I10,B:I4,F:G15.9,D:G23.17,C:G15.9,M:G23.17'
                gives the default formats used for each type.  The TFORM
                fields for the real and complex types indicate will use corresponding
                E and D formats when a G format is specified.
                Note that the length of the field for ASCII strings and
                byte arrays is automatically determined for each column.
       BIT_COLS=   An array of indices of the bit columns.   The data should
                comprise a byte array with the appropriate dimensions.
                If the number of bits per row (see NBIT_COLS)
                is greater than 8, then the first dimension of the array 
                should match the number of input bytes per row.
       BSCALE   Scale floats, longs, or shorts to unsigned bytes (see LSCALE)
       /CREATE   If this keyword is non-zero, then a new FITS file will
                be created regardless of whether the file currently
                exists.  Otherwise when the file already exists,
                a FITS extension will be appended to the existing file
                which is assumed to be a valid FITS file.
       GROUP=   This keyword indicates that GROUPed FITS data is to
                be generated.
                Group should be a 2-D array of the appropriate output type.
                The first dimension will set the number of group parameters.
                The second dimension must agree with the last dimension
                of the Input array.
       ISCALE   Scale floats or longs to short integer (see LSCALE)
       LOGICAL_COLS=  An array of indices of the logical column numbers.
                These should start with the first column having index 0.
                The structure element should either be an array of characters
                with the values 'T' or 'F', or an array of bytes having the 
                values byte('T'), byte('F') or 0b.     The use of bytes allows
                the specification of undefined values (0b).
       LSCALE   Scale floating point numbers to long integers.
                This keyword may be specified in three ways.
                /LSCALE (or LSCALE=1) asks for scaling to be automatically
                determined. LSCALE=value divides the input by value.
                I.e., BSCALE=value, BZERO=0.  Numbers out of range are 
                given the value of NULL if specified, otherwise they are given
                the appropriate extremum value.  LSCALE=(value,value)
                uses the first value as BSCALE and the second as BZERO
                (or TSCALE and TZERO for tables).
       NBIT_COLS=  The number of bits actually used in the bit array.
                This argument must point to an array of the same dimension
                as BIT_COLS.
       NO_TYPES  If the NO_TYPES keyword is specified, then no TTYPE
                keywords will be created for ASCII and BINARY tables.
       No_comment Do not write comment keywords in the header
       NULL=    Value to be written for integers/strings which are
                undefined or unwritable.
       PSCALE=  An array giving scaling parameters for the group keywords.
                It should have the same dimension as the first dimension
                of Group.
       PZERO=   An array giving offset parameters for the group keywords.
                It should have the same dimension as the first dimension
                of Group.
       Separator= This keyword can be specified as a string which will
                be used to separate fields in ASCII tables.  By default
                fields are separated by a blank.
       /SILENT   Suppress informative messages.  Errors will still
                be reported.
       Terminator= This keyword can be specified to provide a string which
                will be placed at the end of each row of an ASCII table.
                No terminator is used when not specified.
                If a non-string terminator is specified (including
                when the /terminator form is used), a new line terminator
                is appended.
       USE_COLNUM  When creating column names for binary and ASCII tables
                MWRFITS attempts to use structure field name
                values.  If USE_COLNUM is specified and non-zero then
                column names will be generated as 'C1, C2, ... 'Cn'
                for the number of columns in the table.
       Version   Print the version number of MWRFITS.

 OPTIONAL OUTPUT KEYWORD:
       Status - 0 if FITS file is successfully written, -1 if there is a
                a problem (e.g. nonexistent directory, or no write permission)
 EXAMPLE:
       Write a simple array:
            a=fltarr(20,20)
            mwrfits,a,'test.fits'

       Append a 3 column, 2 row, binary table extension to file just created.
            a={name:'M31', coords:(30., 20.), distance:2}
            a=replicate(a, 2);
            mwrfits,a,'test.fits'

       Now add on an image extension:
            a=lonarr(10,10,10)
            hdr=("COMMENT  This is a comment line to put in the header", $
                 "MYKEY    = "Some desired keyword value")
            mwrfits,a,'test.fits',hdr

 RESTRICTIONS:
       (1)     Variable length columns are not supported for anything
               other than simple types (byte, int, long, float, double).
       (2)     Empty strings are converted to 1 element blank strings (because
               IDL refuses to write an empty string (0b) from a structure)
 NOTES:
       This multiple format FITS writer is designed to provide a
       single, simple interface to writing all common types of FITS data.
       Given the number of options within the program and the
       variety of IDL systems available it is likely that a number
       of bugs are yet to be uncovered. 

 PROCEDURES USED:
       FXPAR(), FXADDPAR
 MODIfICATION HISTORY:
       Version 0.9: By T. McGlynn   1997-07-23
              Initial beta release.
       Dec 1, 1997, Lindler, Modified to work under VMS.
       Version 0.91: T. McGlynn  1998-03-09
               Fixed problem in handling null primary arrays.
       Version 0.92: T. McGlynn 1998-09-09
               Add no_comment flag and keep user comments on fields.
               Fix handling of bit fields.
       Version 0.93: T. McGlynn 1999-03-10
               Fix table appends on VMS.
       Version 0.93a  W. Landsman/D. Schlegel
               Update keyword values in chk_and_upd if data type has changed 
       Version 0.94: T. McGlynn 2000-02-02
               Efficient processing of ASCII tables.
               Use G rather than E formats as defaults for ASCII tables
                and make the default precision long enough that transformations
                binary to/from ASCII are invertible.
               Some loop indices made long.
               Fixed some ends to match block beginnings.
       Version 0.95: T. McGlynn 2000-11-06
               Several fixes to scaling.  Thanks to David Sahnow for
               documenting the problems.
               Added PCOUNT,GCOUNT keywords to Image extensions.
               Version numbers shown in SIMPLE/XTENSION comments
       Version 0.96: T. McGlynn 2001-04-06
               Changed how files are opened to handle ~ consistently
       Version 1.0: T. McGlynn 2001-12-04
               Unsigned integers,
               64 bit integers.
               Aliases
               Variable length arrays
               Some code cleanup
       Version 1.1: T. McGlynn 2002-2-18
               Fixed major bug in processing of unsigned integers.
               (Thanks to Stephane Beland)
       Version 1.2: Stephane Beland 2003-03-17
               Fixed problem in creating dummy dataset when passing undefined
               data, caused by an update to FXADDPAR routine.
       Version 1.2.1 Stephane Beland 2003-09-10
               Exit gracefully if write priveleges unavailable
       Version 1.3 Wayne Landsman 2003-10-24
               Don't use EXECUTE() statement if on a virtual machine
       Version 1.3a Wayne Landsman 2004-5-21
               Fix for variable type arrays
       Version 1.4 Wayne Landsman 2004-07-16
               Use STRUCT_ASSIGN when modifying structure with pointer tags
       Version 1.4a Wayne Landsman 2005-01-03
               Fix writing of empty strings in binary tables 
       Version 1.4b Wayne Landsman 2006-02-23
               Propagate /SILENT keyword to mwr_tablehdr
       Version 1.5 Wayne Landsman  2006-05-24
               Open file using /SWAP_IF_LITTLE_ENDIAN keyword 
               Convert empty strings to 1 element blank strings before writing            
       Version 1.5a Wayne Landsman 2006-06-29
               Fix problem introduced 2006-05-24 with multidimensional strings
       Version 1.5b K. Tolbert 2006-06-29
               Make V1.5a fix work pre-V6.0
       Version 1.5c I.Evans/W.Landsman 2006-08-08
               Allow logical columns to be specified as bytes 
       Version 1,5d K. Tolbert 2006-08-11 
               Make V1.5a fix work for scalar empty string
       Version 1.6  W. Landsman  2006-09-22
               Assume since V5.5, remove VMS support
       Version 1.6a  W. Landsman  2006-09-22
               Don't right-justify strings 
       Version 1.7  W. Landsman  2009-01-12
               Added STATUS output keyword
       Version 1.7a W. Landsman 2009-04-10
               Since V6.4 strings are no longer limited to 1024
               elements 
       Version 1.8 Pierre Chanial 2009-06-23
               trim alias, implement logical TFORM 'L', don't
               add space after tform key.
       Version 1.9 W. Landsman 2009-07-20
               Suppress compilation messages of supporting routines
       Version 1.10 W. Landsman 2009-09-30
               Allow TTYPE values of 'T' and 'F', fix USE_COLNUM for bin tables
       Version 1.11 W. Landsman 2010-11-18
               Allow LONG64 number of bytes, use V6.0 notation

(See $IDLUTILS_DIR/goddard/pro/fits/mwrfits.pro)

NGP

 NAME:
       NGP

 PURPOSE:
       Interpolate an irregularly sampled field using Nearest Grid Point

 EXPLANATION:
       This function interpolates irregularly gridded points to a
       regular grid using Nearest Grid Point.

 CATEGORY:
       Mathematical functions, Interpolation

 CALLING SEQUENCE:
       Result = NGP, VALUE, POSX, NX[, POSY, NY, POSZ, NZ, 
                     /AVERAGE, /WRAPAROUND, /NO_MESSAGE]

 INPUTS:
       VALUE: Array of sample weights (field values). For e.g. a
              temperature field this would be the temperature and the
              keyword AVERAGE should be set. For e.g. a density field
              this could be either the particle mass (AVERAGE should
              not be set) or the density (AVERAGE should be set).
       POSX:  Array of X coordinates of field samples, unit indices: [0,NX>.
       NX:    Desired number of grid points in X-direction.
       
 OPTIONAL INPUTS:
      POSY: Array of Y coordinates of field samples, unit indices: [0,NY>.
      NY:   Desired number of grid points in Y-direction.
      POSZ: Array of Z coordinates of field samples, unit indices: [0,NZ>.
      NZ:   Desired number of grid points in Z-direction.

 KEYWORD PARAMETERS:
       AVERAGE:    Set this keyword if the nodes contain field samples
                   (e.g. a temperature field). The value at each grid
                   point will then be the average of all the samples
                   allocated to it. If this keyword is not set, the
                   value at each grid point will be the sum of all the
                   nodes allocated to it (e.g. for a density field from
                   a distribution of particles). (D=0). 
       WRAPAROUND: Set this keyword if the data is periodic and if you
                   want the first grid point to contain samples of both
                   sides of the volume (see below). (D=0).
       NO_MESSAGE: Suppress informational messages.

 Example of default NGP allocation: n0=4, *=gridpoint.

     0   1   2   3     Index of gridpoints
     *   *   *   *     Grid points
   |---|---|---|---|   Range allocated to gridpoints ([0.0,1.0> --> 0, etc.)
   0   1   2   3   4   posx

 Example of NGP allocation for WRAPAROUND: n0=4, *=gridpoint.

   0   1   2   3         Index of gridpoints
   *   *   *   *         Grid points
 |---|---|---|---|--     Range allocated to gridpoints ([0.5,1.5> --> 1, etc.)
   0   1   2   3   4=0   posx


 OUTPUTS:
       Prints that a NGP interpolation is being performed of x
       samples to y grid points, unless NO_MESSAGE is set. 

 RESTRICTIONS:
       All input arrays must have the same dimensions.
       Postition coordinates should be in `index units' of the
       desired grid: POSX=[0,NX>, etc.

 PROCEDURE:
       Nearest grid point is determined for each sample.
       Samples are allocated to nearest grid points.
       Grid point values are computed (sum or average of samples).

 EXAMPLE:
       nx = 20
       ny = 10
       posx = randomu(s,1000)
       posy = randomu(s,1000)
       value = posx^2+posy^2
       field = ngp(value,posx*nx,nx,posy*ny,ny,/average)
       surface,field,/lego

 NOTES:
       Use tsc.pro or cic.pro for a higher order interpolation schemes.    A 
       standard reference for these interpolation methods is:   R.W. Hockney 
       and J.W. Eastwood, Computer Simulations Using Particles (New York: 
       McGraw-Hill, 1981).
 MODIFICATION HISTORY:
       Written by Joop Schaye, Feb 1999.
       Check for LONG overflow  P. Riley/W. Landsman   December 1999

(See $IDLUTILS_DIR/goddard/pro/math/ngp.pro)

NINT

 NAME:
	NINT
 PURPOSE:
	Nearest integer function.
 EXPLANATION:   
	NINT() is similar to the intrinsic ROUND function, with the following
	two differences:
	(1) if no absolute value exceeds 32767, then the array is returned as
		as a type INTEGER instead of LONG
	(2) NINT will work on strings, e.g. print,nint(['3.4','-0.9']) will
		give [3,-1], whereas ROUND() gives an error message

 CALLING SEQUENCE:
	result = nint( x, [ /LONG] )

 INPUT:
	X - An IDL variable, scalar or vector, usually floating or double
		Unless the LONG keyword is set, X must be between -32767.5 and 
		32767.5 to avoid integer overflow

 OUTPUT
	RESULT - Nearest integer to X

 OPTIONAL KEYWORD INPUT:
	LONG - If this keyword is set and non-zero, then the result of NINT
		is of type LONG.   Otherwise, the result is of type LONG if
		any absolute values exceed 32767, and type INTEGER if all
		all absolute values are less than 32767.
 EXAMPLE:
	If X = [-0.9,-0.1,0.1,0.9] then NINT(X) = [-1,0,0,1]

 PROCEDURE CALL:
	None:
 REVISION HISTORY:
	Written W. Landsman        January 1989
	Added LONG keyword         November 1991
	Use ROUND if since V3.1.0  June 1993
	Always start with ROUND function    April 1995
	Return LONG values, if some input value exceed 32767
		and accept string values   February 1998 
       Use size(/TNAME) instead of DATATYPE()      October 2001

(See $IDLUTILS_DIR/goddard/pro/misc/nint.pro)

NSTAR

 NAME:
       NSTAR
 PURPOSE:
       Simultaneous point spread function fitting (adapted from DAOPHOT)
 EXPLANATION:
       This PSF fitting algorithm is based on a very old (~1987) version of 
       DAOPHOT, and much better algorithms (e.g. ALLSTAR) are now available
       -- though not in IDL.
       
 CALLING SEQUENCE:
       NSTAR, image, id, xc, yc, mags, sky, group, [ phpadu, readns, psfname,
               magerr, iter, chisq, peak, /PRINT , /SILENT, /VARSKY, /DEBUG ]

 INPUTS:
       image - image array
       id    - vector of stellar ID numbers given by FIND
       xc    - vector containing X position centroids of stars (e.g. as found
               by FIND)
       yc    - vector of Y position centroids
       mags  - vector of aperture magnitudes (e.g. as found by APER)
               If 9 or more parameters are supplied then, upon output
               ID,XC,YC, and MAGS will be modified to contain the new
               values of these parameters as determined by NSTAR.
               Note that the number of output stars may be less than 
               the number of input stars since stars may converge, or 
               "disappear" because they are too faint.
       sky   - vector of sky background values (e.g. as found by APER)
       group - vector containing group id's of stars as found by GROUP

 OPTIONAL INPUT:
       phpadu - numeric scalar giving number of photons per digital unit.  
               Needed for computing Poisson error statistics.   
       readns - readout noise per pixel, numeric scalar.   If not supplied, 
               NSTAR will try to read the values of READNS and PHPADU from
               the PSF header.  If still not found, user will be prompted.
       psfname - name of FITS image file containing the point spread
               function residuals as determined by GETPSF, scalar string.  
               If omitted, then NSTAR will prompt for this parameter.

 OPTIONAL OUTPUTS:
       MAGERR - vector of errors in the magnitudes found by NSTAR
       ITER - vector containing the number of iterations required for
               each output star.  
       CHISQ- vector containing the chi square of the PSF fit for each
               output star.
       PEAK - vector containing the difference of the mean residual of
               the pixels in the outer half of the fitting circle and
               the mean residual of pixels in the inner half of the
               fitting circle

 OPTIONAL KEYWORD INPUTS:
       /SILENT - if set and non-zero, then NSTAR will not display its results
               at the terminal
       /PRINT - if set and non-zero then NSTAR will also write its results to
               a file nstar.prt.   One also can specify the output file name
               by setting PRINT = 'filename'.
       /VARSKY - if this keyword is set and non-zero, then the sky level of
               each group is set as a free parameter.
       /DEBUG - if this keyword is set and non-zero, then the result of each
               fitting iteration will be displayed.

 PROCEDURES USED:
       DAO_VALUE(), READFITS(), REMOVE, SPEC_DIR(), STRN(), SXPAR()

 COMMON BLOCK:
       RINTER - contains pre-tabulated values for cubic interpolation
 REVISION HISTORY
       W. Landsman                 ST Systems Co.       May, 1988
       Adapted for IDL Version 2, J. Isensee, September, 1990
       Minor fixes so that PRINT='filename' really prints to 'filename', and
       it really silent if SILENT is set.  J.Wm.Parker HSTX 1995-Oct-31
       Added /VARSKY option   W. Landsman   HSTX      May 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Replace DATATYPE() with size(/TNAME)  W. Landsman November 2001
       Assume since V5.5, remove VMS calls W. Landsman September 2006

(See $IDLUTILS_DIR/goddard/pro/idlphot/nstar.pro)

NULLTRIM

 NAME:
	NULLTRIM
 PURPOSE:
	Trim a string of all characters after and including the first null
 EXPLANATION:
	The null character is an ascii 0b

 CALLING SEQUENCE:
	result = nulltrim( st )

 INPUTS:
	st = input string
 OUTPUTS:
	trimmed string returned as the function value.
 HISTORY:
	D. Lindler  July, 1987
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/nulltrim.pro)

NUTATE

 NAME:
       NUTATE
 PURPOSE:
       Return the nutation in longitude and obliquity for a given Julian date

 CALLING SEQUENCE:
       NUTATE, jd, Nut_long, Nut_obliq

 INPUT:
       jd - Julian ephemeris date, scalar or vector, double precision  
 OUTPUT:
       Nut_long - the nutation in longitude, same # of elements as jd
       Nut_obliq - nutation in latitude, same # of elements as jd

 EXAMPLE:
       (1) Find the nutation in longitude and obliquity 1987 on Apr 10 at Oh.
              This is example 22.a from Meeus
        IDL> jdcnv,1987,4,10,0,jul
        IDL> nutate, jul, nut_long, nut_obliq
             ==> nut_long = -3.788    nut_obliq = 9.443
            
       (2) Plot the large-scale variation of the nutation in longitude 
               during the 20th century

       IDL> yr = 1900 + indgen(100)     ;Compute once a year        
       IDL> jdcnv,yr,1,1,0,jul          ;Find Julian date of first day of year
       IDL> nutate,jul, nut_long        ;Nutation in longitude
       IDL> plot, yr, nut_long

       This plot will reveal the dominant (18.6 year) period, but a finer
       grid is needed to display the shorter periods in the nutation.
 METHOD:
       Uses the formula in Chapter 22 of ``Astronomical Algorithms'' by Jean 
       Meeus (1998, 2nd ed.) which is based on the 1980 IAU Theory of Nutation
       and includes all terms larger than 0.0003".

 PROCEDURES CALLED:
       POLY()                       (from IDL User's Library)
       CIRRANGE, ISARRAY()          (from IDL Astronomy Library)

 REVISION HISTORY:
       Written, W.Landsman (Goddard/HSTX)      June 1996       
       Converted to IDL V5.0   W. Landsman   September 1997
       Corrected minor typos in values of d_lng W. Landsman  December 2000
       Updated typo in cdelt term              December 2000
       Avoid overflow for more than 32767 input dates W. Landsman January 2005

(See $IDLUTILS_DIR/goddard/pro/astro/nutate.pro)

N_BYTES()

 NAME:
       N_bytes()

 PURPOSE:
       To return the total number of bytes in data element

 CALLING SEQUENCE:
       result = N_bytes(a)

 INPUTS:
       a - any idl data element, scalar or array

 OUTPUTS:
       total number of bytes in a is returned as the function value
       (64bit longword scalar)
 NOTES:
       (1) Not valid for object or pointer data types
       (2) For a string array, the number of bytes is computed after conversion
           with the BYTE() function, i.e. each element has the same length,
           equal to the maximum individual string length.

 MODIFICATION HISTORY:
       Version 1  By D. Lindler  Oct. 1986
       Include new IDL data types    W. Landsman          June 2001
       Now return a 64bit integer    W. Landsman          April 2006

(See $IDLUTILS_DIR/goddard/pro/misc/n_bytes.pro)

OBSERVATORY

 NAME:
       OBSERVATORY
 PURPOSE:
       Return longitude, latitude, altitude & time zones of an observatory
 EXPLANATION:
       Given an observatory name, returns a structure giving the longitude,
       latitude, altitude, and time zone 

 CALLING SEQUENCE:
       Observatory, obsname, obs_struct, [ /PRINT ]

 INPUTS:
       obsname - scalar or vector string giving abbreviated name(s) of 
             observatories for which location or time information is requested.
             If obsname is an empty string, then information is returned for 
             all observatories in the database.     See the NOTES: section
             for the list of 41 recognized observatories.   The case of the 
             string does not matter  
 OUTPUTS:
       obs_struct - an IDL structure containing information on  the specified
                 observatories.   The structure tags are as follows: 
       .observatory - abbreviated observatory name
       .name - full observatory name  
       .longitude - observatory longitude in degrees *west* 
       .latitude - observatory latitude in degrees
       .altitude - observatory altitude in meters above sea level
       .tz - time zone, number of hours *west* of Greenwich

 OPTIONAL INPUT KEYWORD:
     /PRINT - If this keyword is set, (or if only 1 parameter is supplied)
             then OBSERVATORY will display information about the specified
             observatories at the terminal
 EXAMPLE:
     Get the latitude, longitude and altitude of Kitt Peak National Observatory

     IDL> observatory,'kpno',obs
     IDL> print,obs.longitude  ==> 111.6 degrees west 
     IDL> print,obs.latitude  ==> +31.9633 degrees
     IDL> print,obs.altitude  ==> 2120 meters above sea level

 NOTES:
   Observatory information is taken from noao$lib/obsdb.dat file in IRAF 2.11
   Currently recognized observatory names are as follows:

  'kpno': Kitt Peak National Observatory
  'ctio': Cerro Tololo Interamerican Observatory
  'eso': European Southern Observatory
  'lick': Lick Observatory
  'mmto': MMT Observatory
  'cfht': Canada-France-Hawaii Telescope
  'lapalma': Roque de los Muchachos, La Palma
  'mso': Mt. Stromlo Observatory
  'sso': Siding Spring Observatory
  'aao': Anglo-Australian Observatory
  'mcdonald': McDonald Observatory
  'lco': Las Campanas Observatory
  'mtbigelow': Catalina Observatory: 61 inch telescope
  'dao': Dominion Astrophysical Observatory
  'spm': Observatorio Astronomico Nacional, San Pedro Martir
  'tona': Observatorio Astronomico Nacional, Tonantzintla
  'Palomar': The Hale Telescope
  'mdm': Michigan-Dartmouth-MIT Observatory
  'NOV': National Observatory of Venezuela
  'bmo': Black Moshannon Observatory
  'BAO': Beijing XingLong Observatory
  'keck': W. M. Keck Observatory
  'ekar': Mt. Ekar 182 cm. Telescope
  'apo': Apache Point Observatory
  'lowell': Lowell Observatory
  'vbo': Vainu Bappu Observatory
  'flwo': Whipple Observatory
  'oro': Oak Ridge Observatory
  'lna': Laboratorio Nacional de Astrofisica - Brazil
  'saao': South African Astronomical Observatory
  'casleo': Complejo Astronomico El Leoncito, San Juan
  'bosque': Estacion Astrofisica Bosque Alegre, Cordoba
  'rozhen': National Astronomical Observatory Rozhen - Bulgaria
  'irtf': NASA Infrared Telescope Facility
  'bgsuo': Bowling Green State Univ Observatory
  'ca': Calar Alto Observatory
  'holi': Observatorium Hoher List (Universitaet Bonn) - Germany
  'lmo': Leander McCormick Observatory
  'fmo': Fan Mountain Observatory
  'whitin': Whitin Observatory, Wellesley College
  'mgio': Mount Graham International Observatory

 PROCEDURE CALLS:
    TEN()             
 REVISION HISTORY:
    Written   W. Landsman                 July 2000
    Corrected sign error for 'holi'   W.L/ Holger Israel    Mar 2008
    Correctly terminate when observatory name not recognized 
                                              S. Koposov, July 2008

(See $IDLUTILS_DIR/goddard/pro/astro/observatory.pro)

ONE_ARROW

 NAME:
       ONE_ARROW
 PURPOSE:
       Draws an arrow labeled with a single character on the current device
 EXPLANATION:
       ONE_ARROW is called, for example, by ARROWS to create a
       "weathervane" showing the N-E orientation of an image.

 CALLING SEQUENCE:
       one_arrow, xcen, ycen, angle, label, CHARSIZE = , THICK = , COLOR = 
                       ARROWSIZE=, FONT =  ]
 INPUT PARAMETERS:
    xcen, ycen = starting point of arrow, floating point scalars,
                 In device coordinates unless /DATA or /NORMAL set
    angle      = angle of arrow in degrees counterclockwise from +X direction
    label      = single-character label (may be blank)

 OUTPUT PARAMETERS:  none

 OPTIONAL INPUT PARAMETERS:
       ARROWSIZE  = 3-element vector defining appearance of arrow.
               For device coordinates the default is  [30.0, 9.0, 35.0], 
               meaning arrow is 30 pixels long; arrowhead lines 9 pixels 
               long and inclined 35 degrees from arrow shaft.     For 
               normalized coordinates the default is divided by 512., for 
               data coordinates the default is multiplied by 
               (!X.crange[1] - !X.crange[0])/512..
       CHARSIZE   = usual IDL meaning, default = 2.0
       COLOR      = name or number give the color to draw the arrow.  See
             cgCOLOR for a list of color names.
       /DATA - If set, then the input position (xcen, ycen) and the ARROWSIZE
                lengths are interpreted as being in data coordinates
       FONT - IDL vector font number to use (1-20).   For example, to write
               the 'N' and 'E' characters in complex script, set font=13
       /NORMAL - If set, then the input position (xcen, ycen) and the ARROWSIZE
                lengths are interpreted as being in normal coordinates
       THICK      = usual IDL meaning, default = 2.0
 EXAMPLE:
       Draw an triple size arrow emanating from the point (212,224)
       and labeled with the character 'S'

       IDL> one_arrow,212,224,270,'S',charsize=3
 PROCEDURE:  
       Calls one_ray to vector-draw arrow.
 MODIFICATION HISTORY:
       Written by R. S. Hill, Hughes STX Corp., 20-May-1992.
       Added font keyword, W.B. Landsman Hughes STX Corp. April 1995
       Modified to work correctly for COLOR=0  J.Wm.Parker, HITC   1995 May 25
       Add /NORMAL and /DATA keywords  W.Landsman    November 2006
       Work with Coyote graphics W. Landsman  February 2011

(See $IDLUTILS_DIR/goddard/pro/misc/one_arrow.pro)

ONE_RAY

 NAME:
       ONE_RAY
 PURPOSE:
       Draw a line with a specified starting point, length, and  angle

 CALLING SEQUENCE:
       one_ray, xcen, ycen, len, angle, terminus, /NODRAW ]

 INPUT PARAMETERS:
       xcen, ycen = starting point in device coordinates, floating point 
                       scalars
       len        = length in pixels, device coordinates
       angle      = angle in degrees counterclockwise from +X direction

 OUTPUT PARAMETERS:
       terminus = two-element vector giving ending point of ray in device
               coordinates

 OPTIONAL KEYWORD INPUT PARAMETERS:
       /nodraw   if non-zero, the ray is not actually drawn, but the terminus
               is still calculated

        Any valid keyword to cgPLOTS can also be passed ot ONE_RAY.   In
        particular, COLOR, THICK, and LINESTYLE control the color, thickness
        and linestyle of the drawn line.
 EXAMPLE:
       Draw a double thickness line of length 32 pixels from (256,256) 
       45 degrees counterclockwise from the X axis

       IDL> one_ray, 256, 256, 32, 45 ,term, THICK = 2

 PROCEDURE:  straightforward matrix arithmetic

 MODIFICATION HISTORY:
    Written by R. S. Hill, Hughes STX Corp., 20-May-1992.
    Modified to work correctly for COLOR=0  J.Wm.Parker  HITC   1995 May 25
    Added _EXTRA keywords to PLOT   W. Landsman   November 2006
    Work with Coyote Graphcis W. Landsman February 2011

(See $IDLUTILS_DIR/goddard/pro/misc/one_ray.pro)

OPLOTERROR

 NAME:
      OPLOTERROR
 PURPOSE:
      Over-plot data points with accompanying X or Y error bars.
 EXPLANATION:
      For use instead of PLOTERROR when the plotting system has already been
      defined. 

 CALLING SEQUENCE:
      oploterror, [ x,]  y, [xerr], yerr,   
            [ /NOHAT, HATLENGTH= , ERRTHICK =, ERRSTYLE=, ERRCOLOR =, 
              /LOBAR, /HIBAR, NSKIP = , NSUM = , /ADDCMD, ... OPLOT keywords ]
 INPUTS:
      X = array of abcissae, any datatype except string
      Y = array of Y values, any datatype except string
      XERR = array of error bar values (along X)
      YERR = array of error bar values (along Y)

 OPTIONAL INPUT KEYWORD PARAMETERS:
 
      /ADDCMD    = Set this keyword if you want to add this command to 
                   a cgWindow.
      /NOHAT     = if specified and non-zero, the error bars are drawn
                  without hats.
      HATLENGTH = the length of the hat lines used to cap the error bars.
                  Defaults to !D.X_VSIZE / 100).
      ERRTHICK  = the thickness of the error bar lines.  Defaults to the
                  THICK plotting keyword.
      ERRSTYLE  = the line style to use when drawing the error bars.  Uses
                  the same codes as LINESTYLE.
     ERRCOLOR =  String (e.g. 'red') or scalar integer (0 - !D.N_TABLE)
              specifying the color to use for the error bars.   See CGCOLOR()
              for a list of possible color names.  See 
              http://www.idlcoyote.com/cg_tips/legcolor.php
              for a warning about the use of indexed color
      NSKIP = Positive Integer specifying the error bars to be plotted.   
            For example, if NSKIP = 2 then every other error bar is 
            plotted; if NSKIP=3 then every third error bar is plotted.   
            Default is to plot every error bar (NSKIP = 1)
      NSUM =  Number of points to average over before plotting, default = 
             !P.NSUM  The errors are also averaged, and then divided by 
             sqrt(NSUM).   This approximation is meaningful only when the 
             neighboring error bars have similar sizes.
 
      /LOBAR = if specified and non-zero, will draw only the -ERR error bars.
      /HIBAR = if specified and non-zero, will draw only the +ERR error bars.
                  If neither LOBAR or HIBAR are set _or_ if both are set,
                  you will get both error bars.  Just specify one if you
                  only want one set.
     Any valid keywords to the OPLOT command (e.g. PSYM, YRANGE) are also 
     accepted by OPLOTERROR via the _EXTRA facility.

 NOTES:
     If only two parameters are input, they are taken as Y and YERR.  If only
     three parameters are input, they will be taken as X, Y and YERR, 
     respectively.

 EXAMPLE:
      Suppose one has X and Y vectors with associated errors XERR and YERR
      and that a plotting system has already been defined:

       (1) Overplot Y vs. X with both X and Y errors and no lines connecting
           the points
                  IDL> oploterror, x, y, xerr, yerr, psym=3

       (2) Like (1) but overplot only the Y errors bars and omits "hats"
                  IDL> oploterror, x, y, yerr, psym=3, /NOHAT

       (3) Like (2) but suppose one has a positive error vector YERR1, and 
               a negative error vector YERR2 (asymmetric error bars)
                  IDL> oploterror, x, y, yerr1, psym=3, /NOHAT,/HIBAR
                  IDL> oploterror, x, y, yerr2, psym=3, /NOHAT,/LOBAR

 PROCEDURE:
      A plot of X versus Y with error bars drawn from Y - YERR to Y + YERR
      and optionally from X - XERR to X + XERR is written to the output device

 WARNING:
      This an enhanced version of the procedure OPLOTERR in the standard RSI
      library.    It was renamed to OPLOTERROR in June 1998 in the IDL 
      Astronomy library.

 MODIFICATION HISTORY:
      Adapted from the most recent version of PLOTERR.  M. R. Greason,
            Hughes STX, 11 August 1992.
      Added COLOR keyword option to error bars W. Landsman   November 1993
      Add ERRCOLOR, use _EXTRA keyword,           W. Landsman, July 1995
      Remove spurious call to PLOT_KEYWORDS     W. Landsman, August 1995
      OPLOT more than 32767 error bars          W. Landsman, Feb 1996
      Added NSKIP keyword                       W. Landsman, Dec 1996
      Added HIBAR and LOBAR keywords, M. Buie, Lowell Obs., Feb 1998
      Rename to OPLOTERROR    W. Landsman    June 1998
      Ignore !P.PSYM when drawing error bars   W. Landsman   Jan 1999
      Handle NSUM keyword correctly           W. Landsman    Aug 1999
      Check limits for logarithmic axes       W. Landsman    Nov. 1999
      Work in the presence of  NAN values     W. Landsman    Dec 2000
      Improve logic when NSUM or !P.NSUM is set  W. Landsman      Jan 2001
      Remove NSUM keyword from PLOTS call    W. Landsman      March 2001
      Only draw error bars with in XRANGE (for speed)  W. Landsman Jan 2002
      Fix Jan 2002 update to work with log plots  W. Landsman Jun 2002
      Added STRICT_EXTRA keyword   W. Landsman     July 2005
      W. Landsman Fixed case of logarithmic axes reversed Mar 2009
      Update for Coyote Graphics  W. Landsman     Feb. 2011 
      Hats were not being plotted by default  W. Landsman Apr 2011

(See $IDLUTILS_DIR/goddard/pro/plot/oploterror.pro)

ORDINAL

 NAME:
	ORDINAL
 PURPOSE:
	Convert an integer to a correct English ordinal string:
 EXPLANATION:
	The first four ordinal strings are "1st", "2nd", "3rd", "4th" ....

 CALLING SEQUENCE:
	result = ordinal( num )

 INPUT PARAMETERS:
	num = number to be made an ordinal.  If float, will be FIXed.

 OUTPUT PARAMETERS:
	result = string such as '1st' '3rd' '164th' '87th', etc.

 MODIFICATION HISTORY:  
	Written by R. S. Hill, STX, 8 Aug. 1991
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/ordinal.pro)

PARTVELVEC

 NAME:
      PARTVELVEC

 PURPOSE:
       Plot the velocity vectors of particles at their positions
 EXPLANATION:
       This procedure plots the velocity vectors of particles (at the
       positions of the particles).

 CATEGORY:
       Plotting, Two-dimensional.

 CALLING SEQUENCE:
       PARTVELVEC, VELX, VELY, POSX, POSY [, X, Y]

 INPUTS:
       VELX:  An array of any dimension, containing the x-components
              of the particle velocities.
       VELY:  An array of the same dimension as velx, containing the
              y-components of the particle velocities.
       POSX:  An array of the same dimension as velx, containing the
              x-components of the particle positions.
       POSY:  An array of the same dimension as velx, containing the
              y-components of the particle positions.

 OPTIONAL INPUTS:
       X:   Optional abcissae values. X must be a vector.
       Y:   Optional ordinate values. Y must be a vector. If only X
            is specified, then Y is taken equal to be equal to X.

 OPTIONAL INPUT KEYWORD PARAMETERS:
       FRACTION:   The fraction of the vectors to plot. They are
                   taken at random from the complete sample.    Default is
              FRACTION = 1.0, use all vectors

       LENGTH:     The maximum vectorlength relative to the plot data
                   window.   Default = 0.08

       COLOR:      Color for the vectors, axes and titles by string name or
                   number (see cgCOLOR).   Note that if VECCOLORS is 
                   supplied, then the COLOR keyword still specifies the 
                   color of the axes and title.    Default  = 'Opposite'

       OVER:       Plot over the previous plot

       VECCOLORS:  The vector colors. Must be either a scalar, or
                   a vector (nmeric or string) the same size as VELX. 
                   Set to COLOR by default.
       WINDOW - Set this keyword to plot to a resizeable graphics window

       Plot        All other keywords available to cgPlot (e.g. AXISCOLOR,
       Keywords:   LINESTYLE, XRANGE) are available (via _EXTRA)

 OUTPUTS:
       This procedure plots the velocity vectors (VELX,VELY) at the
       positions of the particles, (POSX,POSY). If X and Y are not
       specified, then the size of the plot is such that all vectors
       just fit within in the plot data window.

 SIDE EFFECTS:
       Plotting on the current device is performed.

 EXAMPLE:
       Generate some particle positions and velocities.

         POSX=RANDOMU(seed,200)
         POSY=RANDOMU(seed,200)
         VELX=RANDOMU(seed,200)-0.5
         VELY=RANDOMU(seed,200)-0.5

       Plot the particle velocities.

         PARTVELVEC, VELX, VELY, POSX, POSY

       Example using vector colors.

         POSX=RANDOMU(seed,200)
         POSY=RANDOMU(seed,200)
         VELX=RANDOMU(seed,200)-0.5
         VELY=RANDOMU(seed,200)-0.5
         magnitude = SQRT(velx^2 + vely^2)
         LOADCT, 5, NCOLORS=254, BOTTOM=1 ; Load vector colors
         colors = BytScl(magnitude, Top=254) + 1B
         PARTVELVEC, VELX, VELY, POSX, POSY, COLOR='green', VECCOLORS=colors

 MODIFICATION HISTORY:
       Written by:  Joop Schaye (jschaye@astro.rug.nl), Sep 1996.
       Added /OVER keyword   Theo Brauers (th.brauers@fz-juelich.de) Jul 2002
       Added VECCOLORS keyword. David Fanning (david@dfanning.com) March, 2005
       Incorporate the Coyote Graphics (cg) plot programs  WL  January 2011

(See $IDLUTILS_DIR/goddard/pro/plot/partvelvec.pro)

PCA

 NAME:
    PCA

 PURPOSE:
    Carry out a Principal Components Analysis (Karhunen-Loeve Transform)
 EXPLANATION:
    Results can be directed to the screen, a file, or output variables
    See notes below for comparison with the intrinsic IDL function PCOMP.

 CALLING SEQUENCE:
    PCA, data, eigenval, eigenvect, percentages, proj_obj, proj_atr, 
             [MATRIX =, TEXTOUT = ,/COVARIANCE, /SSQ, /SILENT ]

 INPUT PARAMETERS:
     data -  2-d data matrix, data(i,j) contains the jth attribute value
               for the ith object in the sample.    If N_OBJ is the total
               number of objects (rows) in the sample, and N_ATTRIB is the 
               total number of attributes (columns) then data should be
               dimensioned N_OBJ x N_ATTRIB.         

 OPTIONAL INPUT KEYWORD PARAMETERS:
     /COVARIANCE - if this keyword is set, then the PCA will be carried out
              on the covariance matrix (rare), the default is to use the
              correlation matrix
     /SILENT - If this keyword is set, then no output is printed
     /SSQ - if this keyword is set, then the PCA will be carried out on
               on the sums-of-squares & cross-products matrix (rare)
     TEXTOUT - Controls print output device, defaults to !TEXTOUT

              textout=1       TERMINAL using /more option
              textout=2       TERMINAL without /more option
              textout=3       <program>.prt
              textout=4       laser.tmp
              textout=5      user must open file
              textout = filename (default extension of .prt)

 OPTIONAL OUTPUT PARAMETERS:
     eigenval -  N_ATTRIB element vector containing the sorted eigenvalues
     eigenvect - N_ATRRIB x N_ATTRIB matrix containing the corresponding 
               eigenvectors
     percentages - N_ATTRIB element containing the cumulative percentage 
             variances associated with the principal components
     proj_obj - N_OBJ by N_ATTRIB matrix containing the projections of the 
             objects on the principal components
     proj_atr - N_ATTRIB by N_ATTRIB matrix containing the projections of 
               the attributes on the principal components

 OPTIONAL OUTPUT PARAMETER
      MATRIX   = analysed matrix, either the covariance matrix if /COVARIANCE
              is set, the "sum of squares and cross-products" matrix if
              /SSQ is set, or the (by default) correlation matrix.    Matrix
              will have dimensions N_ATTRIB x N_ATTRIB

 NOTES:
      This procedure performs Principal Components Analysis (Karhunen-Loeve
      Transform) according to the method described in "Multivariate Data 
      Analysis" by Murtagh & Heck [Reidel : Dordrecht 1987], pp. 33-48.
      See  http://astro.u-strasbg.fr/~fmurtagh/mda-sw/

      Keywords /COVARIANCE and /SSQ are mutually exclusive.

      The printout contains only (at most) the first seven principle 
      eigenvectors.    However, the output variables EIGENVECT contain 
      all the eigenvectors
       
      Different authors scale the covariance matrix in different ways.
      The eigenvalues output by PCA may have to be scaled by 1/N_OBJ or
      1/(N_OBJ-1) to agree with other calculations when /COVAR is set.

      PCA uses the non-standard system variables !TEXTOUT and !TEXTUNIT.
      These can be added to one's session using the procedure ASTROLIB.

      The intrinsic IDL function PCOMP  duplicates most
      most of the functionality of PCA, but uses different conventions and
      normalizations.   Note the following:

   (1) PCOMP requires a N_ATTRIB x N_OBJ input array; this is the transpose
         of what PCA expects
   (2) PCA uses standardized variables for the correlation matrix:  the input 
        vectors are set to a  mean of zero and variance of one and divided by 
        sqrt(n); use the /STANDARDIZE keyword to PCOMP for a direct comparison.
   (3) PCA (unlike PCOMP) normalizes the eigenvectors by the square root
         of the eigenvalues.
   (4) PCA returns cumulative percentages; the VARIANCES keyword of PCOMP
         returns the variance in each variable
   (5) PCOMP divides the eigenvalues by (1/N_OBJ-1) when the covariance matrix
          is used.

 EXAMPLE:
      Perform a PCA analysis on the covariance matrix of a data matrix, DATA,
      and write the results to a file

      IDL> PCA, data, /COVAR, t = 'pca.dat'

      Perform a PCA analysis on the correlation matrix.   Suppress all 
      printing, and save the eigenvectors and eigenvalues in output variables

      IDL> PCA, data, eigenval, eigenvect, /SILENT

 PROCEDURES CALLED:
      TEXTOPEN, TEXTCLOSE

 REVISION HISTORY:
      Immanuel Freedman (after Murtagh F. and Heck A.).     December 1993
      Wayne Landsman, modified I/O              December 1993
      Fix MATRIX output, remove GOTO statements   W. Landsman August 1998      
      Changed some index variable to type LONG    W. Landsman March 2000
      Fix error in computation of proj_atr, see Jan 1990 fix in 
       http://astro.u-strasbg.fr/~fmurtagh/mda-sw/pca.f   W. Landsman Feb 2008

(See $IDLUTILS_DIR/goddard/pro/math/pca.pro)

PENT

 NAME:
       PENT
 PURPOSE:
       Return the information entropy of a time series
 EXPLANATION:
       This function will return S, the information entropy of a time series
       for a set of trial periods 

 CATEGORY:
       Time series analysis, period finding, astronomical utilities.

 CALLING SEQUENCE:
       Result = PENT(P, T, X, [N, M ] )

 INPUTS:
       P - array of trial period values.
       T - array of observation times (same units as P).
       X - array of observations.

 OPTIONAL INPUTS:
       N   - If  four parameters are given then the 4th parameter is assumed
               to be N. Then NxN boxes are used to calculate S.
       M,N - If five parameters are given then parameter 4 is M and parameter
               5 is N. S is then calculated using MxN boxes - M partitions for the
               phase and N partitions for the data.
       
 OUTPUTS:
       This function returns S, the information entropy of the time series for
       the periods given in P as defined by Cincotta, Me'ndez & Nu'n~ez
       (Astrophysical Journal 449, 231-235, 1995). The minima of S occur at
       values of P where X shows periodicity.
   
 PROCEDURE:
       The procedure involves dividing the phase space into N^2 partitions 
       (NxN boxes) and then calculating:
       
               __ N^2
         S = - \        mu_i . ln(mu_i)  for all mu_i <> 0
               /_  
                 i = 1 

       where  mu_i is the number of data points in partition i normalised by 
       the number of partitions.

       The option of using MxN boxes is an additional feature of this routine.

 EXAMPLE:

       To generate a similar sythetic data set to Cincotta et al. we
        do the following:

       IDL> P0 = 173.015                        ; Fundamental period
       IDL> T = randomu(seed,400)*15000         ; 400 random observation times
       IDL> A0 = 14.0                           ; Mean magnitude
       IDL> M0 = -0.5  * sin(2*!pi*T/P0)        ; Fundamental mode
       IDL> M1 = -0.15 * sin(4*!pi*T/P0)        ; 1st harmonic
       IDL> M2 = -0.05 * sin(6*!pi*T/P0)        ; 2nd harmonic
       IDL> sig = randomu(seed,400)*0.03        ; noise
       IDL> U = A0 + M0 + M1 + M2 + sig         ; Synthetic data
       IDL> Ptest = 100. + findgen(2000)/2.     ; Trial periods 
       IDL> S = pent(Ptest,T,U)                 ; Calculate S
               ... this takes a few seconds ...
       IDL> plot,Ptest,S,xtitle="P",ytitle="S"  ; plot S v. P
       IDL> print,Ptest(where(S eq min(S)))     ; Print best period (+/- 0.5)

       The plot produced should be similar to Fig. 2 of Cincotta et al.

 RESTRICTIONS:

       My own (limited) experience with this routine suggests that it is not
       as good as other techniques for finding  weak,  multi-periodic signals in 
       poorly sampled  data, but is good for establishing periods of eclipsing
       binary stars when M is quite large (try MxN = 64x16, 128x16 or even 
       256x16).  This suggests it may be good for other periodic light curves 
       (Cepheids, RR Lyrae etc.).
       I would be glad to receive reports of other peoples experience with
       this technique (e-mail pflm@bro730.astro.ku.dk).

 MODIFICATION HISTORY:
       Written by:   Pierre Maxted, 14Sep95
       Modifications:
       Normalisation of S corrected, T-min(T) taken out of loop.
               -  Pierre Maxted, 15Sep95
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/pent.pro)

PICKCOLORNAME

NAME:
PICKCOLORNAME

PURPOSE:

The purpose of this program is to provide a blocking
or modal widget interface for selecting a color "name".
The program uses colors familiar to the cgColor program,
and is often used to select a color name for passing to cgColor.

AUTHOR:

FANNING SOFTWARE CONSULTING:
David Fanning, Ph.D.
1645 Sheely Drive
Fort Collins, CO 80526 USA
Phone: 970-221-0438
E-mail: david@idlcoyote.com
Coyote's Guide to IDL Programming: http://www.idlcoyote.com

CATEGORY:

Graphics, Color Specification.

CALLING SEQUENCE:

colorName = PickColorName(startColorName)

OPTIONAL INPUT PARAMETERS:

startColorName: A string with the "name" of the color. Colors available are these:

Almond Antique White Aquamarine Beige Bisque Black
Blue Blue Violet Brown Burlywood Cadet Blue Charcoal
Chartreuse Chocolate Coral Cornflower Blue Cornsilk Crimson
Cyan Dark Goldenrod Dark Gray Dark Green Dark Khaki Dark Orchid
Dark Red Dark Salmon Dark Slate Blue Deep Pink Dodger Blue Firebrick
Forest Green Gold Goldenrod Gray Green Green Yellow
Honeydew Hot Pink Indian Red Ivory Khaki Lavender
Lawn Green Light Coral Light Cyan Light Gray Light Salmon Light Sea Green
Light Yellow Lime Green Linen Magenta Maroon Medium Gray
Medium Orchid Moccasin Navy Olive Olive Drab Orange
Orange Red Orchid Pale Goldenrod Pale Green Papaya Peru
Pink Plum Powder Blue Purple Red Rose
Rosy Brown Royal Blue Saddle Brown Salmon Sandy Brown Sea Green
Seashell Sienna Sky Blue Slate Blue Slate Gray Snow
Spring Green Steel Blue Tan Teal Thistle Tomato
Turquoise Violet Violet Red Wheat White Yellow

The color WHITE is used if this parameter is absent.

If the BREWER keyword is set, you can use the Brewer Color names:

WT1 WT2 WT3 WT4 WT5 WT6 WT7 WT8
TAN1 TAN2 TAN3 TAN4 TAN5 TAN6 TAN7 TAN8
BLK1 BLK2 BLK3 BLK4 BLK5 BLK6 BLK7 BLK8
GRN1 GRN2 GRN3 GRN4 GRN5 GRN6 GRN7 GRN8
BLU1 BLU2 BLU3 BLU4 BLU5 BLU6 BLU7 BLU8
ORG1 ORG2 ORG3 ORG4 ORG5 ORG6 ORG7 ORG8
RED1 RED2 RED3 RED4 RED5 RED6 RED7 RED8
PUR1 PUR2 PUR3 PUR4 PUR5 PUR6 PUR7 PUR8
PBG1 PBG2 PBG3 PBG4 PBG5 PBG6 PBG7 PBG8
YGB1 YGB2 YGB3 YGB4 YGB5 YGB6 YGB7 YGB8
RYB1 RYB2 RYB3 RYB4 RYB5 RYB6 RYB7 RYB8
TG1 TG2 TG3 TG4 TG5 TG6 TG7 TG8

As of 3 JULY 2008, the BREWER names are always available. If the BREWER keyword is set, only
the BREWER names are available.

INPUT KEYWORD PARAMETERS:

BOTTOM: The colors used in the program must be loaded somewhere
in the color table. This keyword indicates where the colors
start loading. By default BOTTOM is set equal to !D.Table_Size-NCOLORS-1.

BREWER: Set this keyword if you wish to use the Brewer Colors, as defined
in this reference:

http://www.personal.psu.edu/cab38/ColorBrewer/ColorBrewer_intro.html

COLUMNS: Set this keyword to the number of columns the colors should
be arranged in.

FILENAME: The string name of an ASCII file that can be opened to read in
color values and color names. There should be one color per row
in the file. Please be sure there are no blank lines in the file.
The format of each row should be:

redValue greenValue blueValue colorName

Color values should be between 0 and 255. Any kind of white-space
separation (blank characters, commas, or tabs) are allowed. The color
name should be a string, but it should NOT be in quotes. A typical
entry into the file would look like this:

255 255 0 Yellow

GROUP_LEADER: This identifies a group leader if the program is called
from within a widget program. Note that this keyword MUST be provided
if you want to guarantee modal widget functionality. (If you don't know
what this means, believe me, you WANT to use this keyword, always.)

INDEX: This keyword identifies a color table index where the selected color
is to be loaded when the program exits. The default behavior is to restore
the input color table and NOT load a color.

TITLE: This keyword accepts a string value for the window title. The default
is "Select a Color".

OUTPUT KEYWORD PARAMETERS:

CANCEL: On exit, this keyword value is set to 0 if the user selected
the ACCEPT button. IF the user selected the CANCEL button, or
closed the window in any other way, this keyword value is set to 1.

COMMON BLOCKS:

None.

SIDE EFFECTS:

Colors are loaded in the current color table. The input color table
is restored when the program exits. This will only be noticable on
8-bit displays. The startColorName is returned if the user cancels
or destroys the widget before a selection is made. Users should
check the CANCEL flag before using the returned color.

EXAMPLE:

To call the program from the IDL comamnd line:

IDL> color = PickColorName("red") & Print, color

To call the program from within a widget program:

color = PickColorName("red", Group_Leader=event.top) & Print, color

MODIFICATION HISTORY:

Written by: David W. Fanning, 31 August 2000.
Modified program to read colors from a file and to use more
colors on 24-bit platforms. 16 October 2000. DWF.
Added the COLUMNS keyword. 16 October 2000. DWF.
Fixed a small problem with mapping a modal widget. 2 Jan 2001. DWF
Now drawing small box around each color. 13 March 2003. DWF.
Added eight new colors. Total now of 104 colors. 11 August 2005. DWF.
Modified GUI to display system colors. 13 Dec 2005. DWF.
Added BREWER keyword to allow Brewer Colors. 15 May 2008. DWF.
Added all BREWER names to the default naming scheme. 3 July 2008. DWF.
Set a size for the color name label widget. Otherwise, the widget always
jumps back to the center of the display when I select a color on UNIX
machines. Also had to remove TLB updating with UPDATE keyword to avoid
tickling the same IDL bug. Sigh... 13 March (Friday) 2009.
Removed system color names, since these are no longer available in cgColor.
27 Nov 2010. DWF

(See $IDLUTILS_DIR/goddard/pro/coyote/pickcolorname.pro)

PIXCOLOR

 NAME:
	PIXCOLOR
 PURPOSE:
	Assign colors to specified pixel values in a color lookup table
 EXPLANATION:
       Colors can be specified either from the list in cgcolor 
       (http://www.idlcoyote.com/programs/cgcolor.pro ) or as 1 letter 
       abbreviations for 8 common colors.

 CALLING SEQUENCE:
      	PIXCOLOR, pixvalue, color         ;Set color at specified pixel values

 INPUT PARMETERS:
	pixvalue - value or range of pixel values whose color will be modified.
		A single pixel value may be specified by an integer
		If a range of values is specified, then it must be written
		as a string, with a colon denoting the range (e.g.'102:123')
		If omitted, program will prompt for this parameter.

  OPTIONAL INPUT PARAMETER
	color - scalar string specifying either a full color name available in
               CGCOLOR, or a  single character string giving one of the 
               specified colors: 'R' (red), 'B' (blue), 'G' (green)
		'Y' (yellow), 'T' (turquoise), 'V' (violet), 'W' (white)
		or 'D' (dark).  If omitted, program will prompt for this 
		parameter.

 OUTPUTS:
	None
 PROCEDURE:
	TVLCT is used in RGB mode to load the specified pixel values.

 EXAMPLE:
	Set pixel values of 245 to a color of red

	IDL> pixcolor,245,'R'

       Set pixel values 120 to 150 to Magenta

       IDL> pixcolor,'120:150','Magenta'      
 REVISION HISTORY:
	Written, W. Landsman ST Systems Corp.		February, 1987
	Converted to IDL V5.0   W. Landsman   September 1997
       Allow specification of cgcolor names   April 2011

(See $IDLUTILS_DIR/goddard/pro/tv/pixcolor.pro)

PIXWT

 NAME:
	PIXWT
 PURPOSE: 
	Circle-rectangle overlap area computation.
 DESCRIPTION:
	Compute the fraction of a unit pixel that is interior to a circle.
	The circle has a radius r and is centered at (xc, yc).  The center of
	the unit pixel (length of sides = 1) is at (x, y).

 CATEGORY:
	CCD data processing
 CALLING SEQUENCE:
	area = Pixwt( xc, yc, r, x, y )
 INPUTS:
	xc, yc : Center of the circle, numeric scalars
	r      : Radius of the circle, numeric scalars
	x, y   : Center of the unit pixel, numeric scalar or vector
 OPTIONAL INPUT PARAMETERS:
	None.
 KEYWORD PARAMETERS:
	None.
 OUTPUTS:
	Function value: Computed overlap area.
 EXAMPLE:
       What is the area of overlap of a circle with radius 3.44 units centered
       on the point 3.23, 4.22 with the pixel centered at [5,7]

       IDL> print,pixwt(3.23,4.22,3.44,5,7)  ==>  0.6502
 COMMON BLOCKS:
    None.
 PROCEDURE:
	Divides the circle and rectangle into a series of sectors and
	triangles.  Determines which of nine possible cases for the
	overlap applies and sums the areas of the corresponding sectors
	and triangles.    Called by aper.pro

 NOTES:
      If improved speed is needed then a C version of this routines, with
      notes on how to linkimage it to IDL is available at   
       ftp://ftp.lowell.edu/pub/buie/idl/custom/

 MODIFICATION HISTORY:
     Ported by Doug Loucks, Lowell Observatory, 1992 Sep, from the
    routine pixwt.c, by Marc Buie.

(See $IDLUTILS_DIR/goddard/pro/idlphot/pixwt.pro)

PKFIT

 NAME:
	PKFIT
 PURPOSE:
	Subroutine of  GETPSF to perform a one-star least-squares fit 
 EXPLANATION:
	Part of the DAOPHOT PSF photometry sequence

 CALLING SEQUENCE:
	PKFIT, f, scale, x, y, sky, radius, ronois, phpadu, gauss, psf, 
				errmag, chi, sharp, Niter, /DEBUG 
 INPUTS:
	F      - NX by NY array containing actual picture data.           
	X, Y   - the initial estimates of the centroid of the star relative
		to the corner (0,0) of the subarray.  Upon return, the
		final computed values of X and Y will be passed back to the
		calling routine.
	SKY  -   the local sky brightness value, as obtained from APER
	RADIUS-  the fitting radius-- only pixels within RADIUS of the
		instantaneous estimate of the star's centroid will be
		included in the fit, scalar
	RONOIS - readout noise per pixel, scalar
	PHPADU - photons per analog digital unit, scalar
	GAUSS -  vector containing the values of the five parameters defining
		the analytic Gaussian which approximates the core of the PSF.
	PSF   -  an NPSF by NPSF look-up table containing corrections from
		the Gaussian approximation of the PSF to the true PSF.

 INPUT-OUTPUT:
	SCALE  - the initial estimate of the brightness of the star,
		expressed as a fraction of the brightness of the PSF.
		Upon return, the final computed value of SCALE will be
		passed back to the calling routine.
 OUTPUTS:
	ERRMAG - the estimated standard error of the value of SCALE
		returned by this routine.
	CHI    - the estimated goodness-of-fit statistic:  the ratio
		of the observed pixel-to-pixel mean absolute deviation from
		the profile fit, to the value expected on the basis of the
		noise as determined from Poisson statistics and the 
		readout noise.
	SHARP  - a goodness-of-fit statistic describing how much broader  
		the actual profile of the object appears than the
		profile of the PSF.
	NITER -  the number of iterations the solution required to achieve
		convergence.  If NITER = 25, the solution did not converge.
		If for some reason a singular matrix occurs during the least-
		squares solution, this will be flagged by setting NITER = -1.

 RESTRICTIONS:
	No parameter checking is performed
 REVISON HISTORY:
	Adapted from the official DAO version of 1985 January 25
	Version 2.0 W. Landsman STX             November 1988
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/idlphot/pkfit.pro)

PLANCK()

 NAME:
       PLANCK()   
 PURPOSE: 
       To calculate the Planck function in units of ergs/cm2/s/A  

 CALLING SEQUENCE: 
       bbflux = PLANCK( wave, temp) 

 INPUT PARAMETERS: 
       WAVE   Scalar or vector giving the wavelength(s) in **Angstroms**
               at which the Planck function is to be evaluated.
       TEMP   Scalar giving the temperature of the planck function in degree K

 OUTPUT PARAMETERS:
       BBFLUX - Scalar or vector giving the blackbody flux (i.e. !pi*Intensity)
               in erg/cm^2/s/A in at the specified wavelength points.

 EXAMPLES:
       To calculate the blackbody flux at 30,000 K every 100 Angstroms between
       2000A and 2900 A
   
       IDL> wave = 2000 + findgen(10)*100
       IDL> bbflux = planck(wave,30000)

       If a star with a blackbody spectrum has a radius R, and distance,d, then
       the flux at Earth in erg/cm^2/s/A will be bbflux*R^2/d^2
 PROCEDURE:
       The wavelength data are converted to cm, and the Planck function
       is calculated for each wavelength point. See Allen (1973), Astrophysical
       Quantities, section 44 for more information.

 NOTES:
       See the procedure planck_radiance.pro in 
       ftp://origin.ssec.wisc.edu/pub/paulv/idl/Radiance/planck_radiance.pro
       for computation of Planck radiance given wavenumber in cm-1 or  
       wavelength in microns 
 MODIFICATION HISTORY:
       Adapted from the IUE RDAF               August, 1989
       Converted to IDL V5.0   W. Landsman   September 1997
       Improve precision of constants    W. Landsman  January 2002

(See $IDLUTILS_DIR/goddard/pro/astro/planck.pro)

PLANET_COORDS

 NAME:
    PLANET_COORDS
 PURPOSE:  
    Find low or high precision RA and DEC for the planets given a date

 EXPLANATION:
    For low precision this routine uses HELIO to get the heliocentric ecliptic
    coordinates of the planets at the given date, then converts these to 
    geocentric ecliptic coordinates ala "Astronomical Algorithms" by Jean 
    Meeus (1991, p 209). These are then converted to RA and Dec using EULER.
    The accuracy between the years 1800 and 2050 is better than 1 arcminute 
    for  the terrestial planets, but reaches 10 arcminutes for Saturn.    
    Before 1850 or after 2050 the accuracy can get much worse.   

    For high precision use the /JPL option ito use the full JPL ephemeris.
 CALLING SEQUENCE:
    PLANET_COORDS, DATE, RA, DEC, [ PLANET = , /JD, /JPL]

 INPUTS:
       DATE - If /JD is not set, then date is a 3-6 element vector containing
              year,month (1-12), day, and optionally hour, minute, & second.
              If /JD is set then DATE is a Julian date.   An advantage of the
              /JD option is that it allows the use of vector dates.
 OUTPUTS:
       RA - right ascension of planet(s), J2000 degrees, double precision
       DEC - declination of   planet(s), J2000 degrees, double precision

 OPTIONAL INPUT KEYWORD:
       PLANET - scalar string giving name of a planet, e.g. 'venus'. Default 
               is to compute coords for all of them (except Earth).
       /JD - If set, then the date parameter should be supplied as Julian date
       JPL - if /JPL set, then PLANET_COORDS will call the procedure 
             JPLEPHINTERP to compute positions using the full JPL ephemeris.   
             The JPL ephemeris FITS file JPLEPH.405 must exist in either the 
             current directory, or in the directory specified by the 
             environment variable ASTRO_DATA.   Alternatively, the JPL keyword
             can be set to the full path and name of the ephemeris file.
             A copy of the JPL ephemeris FITS file JPLEPH.405 is available in
                 http://idlastro.gsfc.nasa.gov/ftp/data/         
 EXAMPLES:
    (1)  Find the RA, Dec of Venus on 1992 Dec 20
          IDL> planet_coords, [1992,12,20], ra,dec    ;Compute for all planets
          IDL> print,adstring(ra[1],dec[1],1)         ;Venus is second planet
     ====> RA = 21 05  2.66  Dec = -18 51 45.7
    This position is 37" from the full DE406 ephemeris position of
          RA = 21 05  5.24        -18 51 43.1

    (2) Return the current RA and Dec of all 8 planets using JPL ephemeris
          IDL> get_juldate, jd                 ;Get current Julian Date
          IDL> planet_coords,jd,ra,dec,/jd,/jpl  ;Find positions of all planets
          IDL> forprint,adstring(ra,dec,0)     ;Display positions   

    (3) Plot the declination of Mars for every day in the year 2001
          IDL> jdcnv,2001,1,1,0,jd      ;Get Julian date of midnight on Jan 1 
               Now get Mars RA,Dec for 365 consecutive days
          IDL> planet_coords,jd+indgen(365),ra,dec,/jd, planet = 'mars'     
          IDL> plot,indgen(365)+1,dec
 NOTES:
          HELIO is based on the two-body problem and neglects interactions 
           between the planets.   This is why the worst results are for
           Saturn.   Use the /JPL option or the online ephemeris generator 
           http://ssd.jpl.nasa.gov/horizons.cgi for more accuracy. 

           The procedure returns astrometric coordinates, i.e. no correction
           for aberration.   A correction for light travel time is applied
           when /JPL is set, but not for the default low-precision calculation.
 PROCEDURES USED:
        JULDATE 
        EULER, HELIO  - if /JPL is not set
        JPLEPHREAD, JPLEPHINTERP - if /JPL is set
 REVISION HISTORY:
        Written P.Plait & W. Landsman     August 2000
        Fixed Julian date conversion   W. Landsman August 2000
        Added /JPL keyword  W. Landsman   July 2001
        Allow vector Julian dates with JPL ephemeris W. Landsman December 2002

(See $IDLUTILS_DIR/goddard/pro/astro/planet_coords.pro)

PLOTERROR

 NAME:
     PLOTERROR
 PURPOSE:
     Plot data points with accompanying X or Y error bars.
 EXPLANATION:
     This is a greatly enhanced version of the standard IDL Library routine
     PLOTERR

 CALLING SEQUENCE:
     ploterror, [ x,]  y, [xerr], yerr [, TYPE=, /NOHAT, HATLENGTH= , NSUM =
                  ERRTHICK=, ERRSTYLE=, ErrcolOR=, NSKIP=, .. PLOT keywords]

 INPUTS:
     X = array of abcissae.
     Y = array of Y values.
     XERR = array of error bar values (along X)
     YERR = array of error bar values (along Y)

 OPTIONAL INPUT KEYWORD PARAMETERS:
     TYPE = type of plot produced.  The possible types are:
              TYPE = 0 :       X Linear - Y Linear  (default)
              TYPE = 1 :       X Linear - Y Log
              TYPE = 2 :       X Log    - Y Linear
              TYPE = 3 :       X Log    - Y Log
              Actually, if 0 is specified, the XLOG and YLOG keywords
              are used.  If these aren't specified, then a linear-linear
              plot is produced.  This keyword is available to maintain
              compatibility with the previous version of PLOTERROR.
     /NOHAT     = if specified and non-zero, the error bars are drawn
              without hats.
     HATLENGTH = the length of the hat lines in device units used to cap the 
              error bars.   Defaults to !D.X_VSIZE / 100).
     ERRTHICK  = the thickness of the error bar lines.  Defaults to the
              THICK plotting keyword.
     ERRSTYLE  = the line style to use when drawing the error bars.  Uses
              the same codes as LINESTYLE.
     ERRCOLOR =  String (e.g. 'red') or scalar integer (0 - !D.N_TABLE)
              specifying the color to use for the error bars.   See CGCOLOR()
              for a list of possible color names.  See 
              http://www.idlcoyote.com/cg_tips/legcolor.php
              for a warning about the use of indexed color
     NSKIP = Integer specifying the error bars to be plotted.   For example,
              if NSKIP = 2 then every other error bar is plotted; if NSKIP=3
              then every third error bar is plotted.   Default is to plot
              every error bar (NSKIP = 1)
     NSUM =  Number of points to average over before plotting, default=!P.NSUM
             The errors are also averaged, and then divided by sqrt(NSUM).   
             This  approximation is meaningful only when the neighboring error
             bars have similar sizes.    PLOTERROR does not pass the NSUM 
             keyword to the PLOT command, but rather computes the binning 
             itself using the  FREBIN function.
     TRADITIONAL - If set to 0 then a black plot is drawn on a white background
             in the graphcis window.   The default value is 1, giving the
             traditional black background for a graphics window.
     WINDOW - Set this keyword to plot to a resizeable graphics window
            

     Any valid keywords to the cgPLOT command (e.g. PSYM, YRANGE, AXISCOLOR  
     SYMCOLOR, ASPECT) are also accepted by PLOTERROR via the _EXTRA facility.

 RESTRICTIONS:
       Arrays must not be of type string, and there must be at least 1 point.
       If only three parameters are input, they will be taken as X, Y and
       YERR respectively.

       PLOTERROR cannot be used for asymmetric error bars.   Instead use
       OPLOTERROR with the /LOBAR and /HIBAR keywords.

       Any data points with NAN values in the X, Y, or error vectors are 
       ignored.
 EXAMPLE:
       Suppose one has X and Y vectors with associated errors XERR and YERR

       (1) Plot Y vs. X with both X and Y errors and no lines connecting
           the points
                  IDL> ploterror, x, y, xerr, yerr, psym=3

       (2) Like (1) but plot only the Y errors bars and omits "hats"
                  IDL> ploterror, x, y, yerr, psym=3, /NOHAT

 WARNING:
       This an enhanced version of the procedure PLOTERR in the standard IDL
       distribution.    It was renamed from PLOTERR to PLOTERROR in June 1998
       in the IDL Astronomy Library to avoid conflict with the RSI procedure.

 PROCEDURE:
       A plot of X versus Y with error bars drawn from Y - YERR to Y + YERR
       and optionally from X - XERR to X + XERR is written to the output device

 PROCEDURE CALLS:
     cgPlot, cgPlots
     FREBIN - used to compute binning if NSUM keyword is present
 MODIFICATION HISTORY:
     William Thompson        Applied Research Corporation  July, 1986
     DMS, April, 1989        Modified for Unix
     Michael R. Greason      ST Systems
     May, 1991               Added most of the plotting keywords, put hats
                               on the error bars.
     K. Venkatakrishna       Added option to plot xerr, May, 1992
     Michael R. Greason      Corrected handling of reversed axes.  Aug. 1992
     W. Landsman             Use _EXTRA keyword                    July 1995
     W. Landsman             Plot more than 32767 points           Feb 1996
     W. Landsman     Fix Y scaling when only XRANGE supplied       Nov 1996
     W. Landsman     Added NSKIP keyword                           Dec 1996
     W. Landsman     Use XLOG, YLOG instead of XTYPE, YTYPE        Jan 1998
     W. Landsman     Rename to PLOTERROR, OPLOTERROR               Jun 1998
     W. Landsman  Better default scaling when NSKIP supplied       Oct 1998 
     W. Landsman  Ignore !P.PSYM when drawing error bars           Jan 1999
     W. Landsman  Handle NSUM keyword correctly                    Aug 1999
     W. Landsman  Fix case of /XLOG but no X error bars            Oct 1999
     W. Landsman  Work in the presence of NAN values               Nov 2000
     W. Landsman  Improve logic when NSUM or !P.NSUM is set        Jan 2001
     W. Landsman  Only draw error bars with in XRANGE (for speed)  Jan 2002
     W. Landsman  Fix Jan 2002 update to work with log plots       Jun 2002
     W. Landsman  Added _STRICT_EXTRA                              Jul 2005
     W. Landsman/D.Nidever Fixed case of logarithmic axes reversed Mar 2009
     W. Landsman/S. Koch  Allow input to be a single point         Jan 2010
     W. Landsman  Add Coyote Graphics                              Feb 2011
     W. Landsman Make keyword name ERRCOLOR instead of ECOLOR 
                 Speedup when no ERRCOLOR defined                  Feb 2011
     D. Fanning Use PLOTS instead of CGPLOTS for speed             Jan 2012

(See $IDLUTILS_DIR/goddard/pro/plot/ploterror.pro)

PLOTHIST

 NAME:
      PLOTHIST
 PURPOSE:
      Plot the histogram of an array with the corresponding abcissa.

 CALLING SEQUENCE:
      plothist, arr, xhist, yhist, [, BIN=, /FILL, /NOPLOT, /OVERPLOT, PEAK=,
                                     /AUTOBIN,  ...plotting keywords]
 INPUTS:
      arr - The array to plot the histogram of.   It can include negative
            values, but non-integral values will be truncated.              

 OPTIONAL OUTPUTS:
      xhist - X vector used in making the plot  
              ( = lindgen( N_elements(h)) * bin + min(arr) )
      yhist - Y vector used in making the plot  (= histogram(arr/bin))

 OPTIONAL INPUT KEYWORDS:
      /AUTOBIN - Automatically determines bin size of the histogram as the
                 square root of the number of samples. Only valid when BIN
                 is not set.
      AXISCOLOR - Color (string or number) of the plotting axes.  
      BIN -  The size of each bin of the histogram,  scalar (not necessarily
             integral).  If not present (or zero), the bin size is set to 1.
      /BOXPLOT - If set, then each histogram data value will be plotted
             "box style" with vertical lines drawn from Y=0 at each end of 
              the bin width
      COLOR - Color (number or string) of the plotted data.    See CGCOLOR
              for a list of available color names. 
      /HALFBIN - Set this keyword to a nonzero value to shift the binning by
              half a bin size.     This is useful for integer data, where e.g.
              the bin for values of 6 will go from 5.5 to 6.5.   The default
              is to set the HALFBIN keyword for integer data, and not for
              non-integer data.     
      /NAN - If set, then check for the occurence of IEEE not-a-number values
      /NOPLOT - If set, will not plot the result.  Useful if intention is to
             only get the xhist and yhist outputs.
      /OVERPLOT - If set, will overplot the data on the current plot.  User
            must take care that only keywords valid for OPLOT are used.
      PEAK - if non-zero, then the entire histogram is normalized to have
             a maximum value equal to the value in PEAK.  If PEAK is
             negative, the histogram is inverted.
      /FILL - if set, will plot a filled (rather than line) histogram.
      /ROTATE - if set, the plot is rotated onto it's side, meaning the bars 
             extend from left to right.  Xaxis corresponds to the count within 
             in each bin.      Useful for placing a histogram plot
             at the side of a scatter plot, as shown at the bottom of
               http://www.dur.ac.uk/j.r.mullaney/pages/software.php
       WINDOW - Set this keyword to plot to a resizeable graphics window


 The following keywords take effect only if the FILL keyword is set:
      FCOLOR - color (string or number) to use for filling the histogram
      /FLINE - if set, will use lines rather than solid color for fill (see
              the LINE_FILL keyword in the cgcolorfill routine)
      FORIENTATION - angle of lines for fill (see the ORIENTATION keyword
              in the cgcolorfill routine)
      FPATTERN - the pattern to use for the fill (see the PATTERN keyword
              in the cgcolorfill routine)
      FSPACING - the spacing of the lines to use in the fill (see the SPACING
              keyword in the cgcolorfill routine)
      FTHICK - the thickness of the lines to use in the fill (see the THICK
              keyword in the cgcolorfill routine)

 Any input keyword that can be supplied to the cgPLOT procedure (e.g. XRANGE,
    AXISCOLOR, LINESTYLE, /XLOG, /YLOG) can also be supplied to PLOTHIST.

 EXAMPLE:
       (1) Create a vector of random 1000 values derived from a Gaussian of 
       mean 0, and sigma of 1.    Plot the histogram of these values with a 
       binsize of 0.1, and use a box plotting style.

       IDL> a = randomn(seed,1000)
       IDL> plothist,a, bin = 0.1, /boxplot

       (2) As before, but fill the plot with diagonal lines at a 45 degree 
           angle

       IDL> plothist,a, bin=0.1, /fill, /fline, forient=45

 NOTES:
       David Fanning has written a similar program HISTOPLOT with more graphics
       options:   See http://www.idlcoyote.com/programs/histoplot.pro
 MODIFICATION HISTORY:
        Written     W. Landsman            January, 1991
        Add inherited keywords W. Landsman        March, 1994
        Use ROUND instead of NINT  W. Landsman   August, 1995
        Add NoPlot and Overplot keywords.   J.Wm.Parker  July, 1997
        Add Peak keyword.   J.Wm.Parker  Jan, 1998
        Add FILL,FCOLOR,FLINE,FPATTERN,FSPACING keywords. J.Wm.Parker Jan, 1998
        Add /NAN keyword        W. Landsman October 2001
        Don't plot out of range with /FILL, added HALFBIN keyword, make
        half bin shift default for integer only W. Landsman/J. Kurk May 2002
        Add BOXPLOT keyword, use exact XRANGE as default W.L.  May 2006
        Allow use of /XLOG and /YLOG keywords  W.L. June 2006
        Adjust Ymin when /YLOG is used  W. L.  Sep 2007
        Added AXISCOLOR keyword, fix color problem with overplots WL Nov 2007
        Check when /NAN is used and all elements are NAN  S. Koposov Sep 2008
        Added /ROTATE keyword to turn plot on its side. J. Mullaney, 2009.
        Added FTHICK keyword for thickness of fill lines. L. Anderson Oct. 2010
        Use Coyote Graphics  W. Landsman Feb 2011
        Explicit XSTYLE, YSTYLE keywords to avoid _EXTRA confusion WL. Aug 2011
        Fix PLOT keyword problem with /ROTATE  WL  Dec 2011

(See $IDLUTILS_DIR/goddard/pro/plot/plothist.pro)

PLOTSYM

NAME:
PLOTSYM
PURPOSE:
Define useful plotting symbols not in the standard !PSYM definitions.
EXPLANATION:
After a symbol has been defined with PLOTSYM, a plotting command should
follow with either PSYM = 8 or !P.PSYM = 8 (see USERSYM)

For additional rotationally symmetric plotting symbols, see VSYM.PRO
or http://www.idlcoyote.com/documents/programs.html#SYMCAT
CALLING SEQUENCE:
PLOTSYM, PSYM,[ PSIZE, /FILL, THICK=, COLOR=]

INPUTS:
PSYM - The following integer values of PSYM will create the
corresponding plot symbols
0 - circle
1 - downward arrow (upper limit), base of arrow begins at plot value value
2 - upward arrow (lower limt)
3 - 5 pointed star
4 - triangle
5 - upside down triangle
6 - left pointing arrow
7 - right pointing arrow
8 - square

Arrows are defined such that their base begins at their origin.

OPTIONAL INPUTS:
PSIZE - Size of the plotting symbol in multiples of the default size
(default PSIZE=1). Does not need to be an integer

OPTIONAL INPUT KEYWORD:
FILL - Parameter indicating whether to fill the symbol (see USERSYM)
The default is 0, unfilled symbol. Does not affect arrows
or character symbols.
THICK - Thickness of unfilled symbols. Default is 1.
COLOR - Color of the symbols, Default is !P.color
OUTPUTS:
None

EXAMPLES:
Plot Y vs. X with filled stars as the symbol, twice the default size
IDL> PLOTSYM, 3 ,2, /FILL ;Plotting symbol is a filled star,
;twice default size
IDL> PLOT,X,Y,PSYM=8 ;Set PSYM = 8 to get star symbol

Now plot Y vs. X with an open circle as the symbol

IDL> PLOTSYM, 0 ;Plotting symbol is a circle
IDL> PLOT,X,Y,PSYM=8

METHOD:
Appropriate X,Y vectors are used to define the symbol and passed to the
USERSYM command.

REVISION HISTORY
Written W. Landsman June 1992
18-JAN-1996 Added a square symbol, HCW.
98Aug20 Added keyword thick parameter - RCB.
April 2001 Added COLOR keyword WBL

(See $IDLUTILS_DIR/goddard/pro/plot/plotsym.pro)

POIDEV

 NAME:
     POIDEV
 PURPOSE:
     Generate a Poisson random deviate
 EXPLANATION:
     Return an integer random deviate drawn from a Poisson distribution with
     a specified mean.    Adapted from procedure of the same name in 
     "Numerical Recipes" by Press et al. (1992), Section 7.3

     NOTE: This routine became partially obsolete in V5.0 with the 
     introduction of the POISSON keyword to the intrinsic functions 
     RANDOMU and RANDOMN.     However, POIDEV is still useful for adding 
     Poisson noise to an existing image array, for which the coding is much 
     simpler than it would be using RANDOMU (see example 1) 
 CALLING SEQUENCE:
     result = POIDEV( xm, [ SEED = ] )

 INPUTS:
     xm - numeric scalar, vector or array, specifying the mean(s) of the 
          Poisson distribution

 OUTPUT:
     result - Long integer scalar or vector, same size as xm

 OPTIONAL KEYWORD INPUT-OUTPUT:
     SEED -  Scalar to be used as the seed for the random distribution.  
             For best results, SEED should be a large (>100) integer.
             If SEED is undefined, then its value is taken from the system 
             clock (see RANDOMU).    The value of SEED is always updated 
             upon output.   This keyword can be used to have POIDEV give 
             identical results on consecutive runs.     

 EXAMPLE:
     (1) Add Poisson noise to an integral image array, im
              IDL> imnoise = POIDEV( im)

     (2) Verify the expected mean  and sigma for an input value of 81
              IDL> p = POIDEV( intarr(10000) + 81)   ;Test for 10,000 points
              IDL> print,mean(p),sigma(p)
     Mean and sigma of the 10000 points should be close to 81 and 9

 METHOD: 
     For small values (< 20) independent exponential deviates are generated 
     until their sum exceeds the specified mean, the number of events 
     required is returned as the Poisson deviate.   For large (> 20) values,
     uniform random variates are compared with a Lorentzian distribution 
     function.

 NOTES:
     Negative values in the input array will be returned as zeros.  

       
 REVISION HISTORY:
      Version 1               Wayne Landsman        July  1992
      Added SEED keyword                            September 1992
      Call intrinsic LNGAMMA function               November 1994
      Converted to IDL V5.0   W. Landsman   September 1997
      Use COMPLEMENT keyword to WHERE()        W. Landsman August 2008

(See $IDLUTILS_DIR/goddard/pro/math/poidev.pro)

POLINT

 NAME:
     POLINT
 PURPOSE:
     Interpolate a set of N points by fitting a polynomial of degree N-1
 EXPLANATION:
     Adapted from algorithm in Numerical Recipes, Press et al. (1992), 
     Section 3.1.

 CALLING SEQUENCE
     POLINT, xa, ya, x, y, [ dy ]
 INPUTS:
     XA - X Numeric vector, all values must be distinct.   The number of
          values in XA should rarely exceed 10 (i.e. a 9th order polynomial)
     YA - Y Numeric vector, same number of elements
     X - Numeric scalar specifying value to be interpolated 

 OUTPUT:
     Y - Scalar, interpolated value in (XA,YA) corresponding to X

 OPTIONAL OUTPUT
     DY - Error estimate on Y, scalar

 EXAMPLE:
     Find sin(2.5) by polynomial interpolation on sin(indgen(10))

               IDL> xa = indgen(10)
               IDL> ya = sin( xa )
               IDL> polint, xa, ya, 2.5, y ,dy
             
     The above method gives  y = .5988 & dy = 3.1e-4  a close
     approximation to the actual sin(2.5) = .5985

 METHOD:
     Uses Neville's algorithm to iteratively build up the correct
     polynomial, with each iteration containing one higher order.

 REVISION HISTORY:
     Written W. Landsman                 January, 1992
     Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/polint.pro)

POLREC

 NAME:
       POLREC
 PURPOSE:
       Convert 2-d polar coordinates to rectangular coordinates.
 CATEGORY:
 CALLING SEQUENCE:
       polrec, r, a, x, y
 INPUTS:
       r, a = vector in polar form: radius, angle (radians).  in
 KEYWORD PARAMETERS:
       Keywords:
         /DEGREES means angle is in degrees, else radians.
 OUTPUTS:
       x, y = vector in rectangular form, double precision     out
 COMMON BLOCKS:
 NOTES:
 MODIFICATION HISTORY:
       R. Sterner. 18 Aug, 1986.
       Johns Hopkins University Applied Physics Laboratory.
       RES 13 Feb, 1991 --- added /degrees.
	Converted to IDL V5.0   W. Landsman   September 1997
       1999 May 03 --- Made double precision.  R. Sterner.

 Copyright (C) 1986, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.

(See $IDLUTILS_DIR/goddard/pro/jhuapl/polrec.pro)

POLYLEG

 NAME:
       POLYLEG

 PURPOSE:
       Evaluate a Legendre polynomial with specified coefficients.
 EXPLANATION:
       Meant to be used analogously to the POLY function in the IDL User's
       Library distribution.

 CALLING SEQUENCE:
       Result = POLYLEG( X, C )        

 INPUTS:
       X - input variable, scalar or vector    
       C - vector of Legendre polynomial coefficients. 
 OUTPUTS:
       POLYLEG returns a result equal to:
               C[0] + C[1]*P_1(x) + C[2]*P_2(x) + ...

       where P_j(x) is the jth Legendre polynomial.   The output will have
       the same dimensions as the input X variable.

 EXAMPLE:
       If x = [0.5, 1.0] and C = [2.4, 1.3, 2.5] then
       print, polyleg(x, c)    ====> [2.7375, 6.20]

       The result can be checked using the first 3 Legendre polynomial terms
       C[0] + C[1]*x + C[2]*(0.5*(3*x^2-1))
 METHOD:
       Uses the recurrence relation of Legendre polynomials
               (n+1)*P_n+1(x) = (2n+1)*x*P_n(x) - n*P_n-1(x)
       evaluated with the Clenshaw recurrence formula, see Numerical Recipes
       by Press et al. (1992), Section 5.5

 REVISION HISTORY:
       Written W. Landsman   Hughes STX Co.        April, 1995    
       Fixed for double precision  W. Landsman     May, 1997
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/polyleg.pro)

POLY_SMOOTH

 NAME:
       POLY_SMOOTH  

 PURPOSE:
       Apply a least-squares (Savitzky-Golay) polynomial smoothing filter
 EXPLANATION:
       Reduce noise in 1-D data (e.g. time-series, spectrum) but retain 
       dynamic range of variations in the data by applying a least squares 
       smoothing polynomial filter,

       Also called the Savitzky-Golay smoothing filter, cf. Numerical
       Recipes (Press et al. 1992, Sec.14.8)

       The low-pass filter coefficients are computed by effectively
       least-squares fitting a polynomial in moving window,
       centered on each data point, so the new value will be the
       zero-th coefficient of the polynomial. Approximate first derivates
       of the data can be computed by using first degree coefficient of
       each polynomial, and so on. The filter coefficients for a specified
       polynomial degree and window width are computed independent of any
       data, and stored in a common block. The filter is then convolved
       with the data array to result in smoothed data with reduced noise,
       but retaining higher order variations (better than SMOOTH).

       This procedure became partially obsolete in IDL V5.4 with the 
       introduction of the SAVGOL function, which computes the smoothing
       coefficients.
 CALLING SEQUENCE:

       spectrum = poly_smooth( data, [ width, DEGREE = , NLEFT = , NRIGHT = 
                                       DERIV_ORDER = ,COEFF = ]

 INPUTS:
       data = 1-D array, such as a spectrum or time-series.

       width = total number of data points to use in filter convolution,
               (default = 5, using 2 past and 2 future data points),
               must be larger than DEGREE of polynomials, and a guideline is to
               make WIDTH between 1 and 2 times the FWHM of desired features.

 OPTIONAL INPUT KEYWORDS:

       DEGREE = degree of polynomials to use in designing the filter
               via least squares fits, (default DEGREE = 2)
               The higher degrees will preserve sharper features.

       NLEFT = # of past data points to use in filter convolution,
               excluding current point, overrides width parameter,
               so that width = NLEFT + NRIGHT + 1.  (default = NRIGHT)

       NRIGHT = # of future data points to use (default = NLEFT).

       DERIV_ORDER = order of derivative desired (default = 0, no derivative).

 OPTIONAL OUTPUT KEYWORD:

       COEFFICIENTS = optional output of the filter coefficients applied,
               but they are all stored in common block for reuse, anyway.
 RESULTS:
       Function returns the data convolved with polynomial filter coefs.

 EXAMPLE:

       Given a wavelength - flux spectrum (w,f), apply a 31 point quadratic
       smoothing filter and plot

       IDL> cgplot, w, poly_smooth(f,31) 
 COMMON BLOCKS:
       common poly_smooth, degc, nlc, nrc, coefs, ordermax

 PROCEDURE:
       As described in Numerical Recipies, 2nd edition sec.14.8, 
       Savitsky-Golay filter.
       Matrix of normal eqs. is formed by starting with small terms
       and then adding progressively larger terms (powers).
       The filter coefficients of up to derivative ordermax are stored
       in common, until the specifications change, then recompute coefficients.
       Coefficients are stored in convolution order, zero lag in the middle.

 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC 1993.
       Converted to IDL V5.0   W. Landsman   September 1997
       Use /EDGE_TRUNCATE keyword to CONVOL  W. Landsman March 2006

(See $IDLUTILS_DIR/goddard/pro/math/poly_smooth.pro)

POSANG

 NAME:
       POSANG
 PURPOSE:
       Computes rigorous position angle of source 2 relative to source 1
       
 EXPLANATION:
       Computes the rigorous position angle of source 2 (with given RA, Dec) 
       using source 1 (with given RA, Dec) as the center.
 
 CALLING SEQUENCE:
       POSANG, U, RA1, DC1, RA2, DC2, ANGLE

 INPUTS:
       U    -- Describes units of inputs and output:
               0:  everything radians
               1:  RAx in decimal hours, DCx in decimal
                       degrees, ANGLE in degrees
       RA1  -- Right ascension of point 1
       DC1  -- Declination of point 1
       RA2  -- Right ascension of point 2
       DC2  -- Declination of point 2

   OUTPUTS:
       ANGLE-- Angle of the great circle containing [ra2, dc2] from
               the meridian containing [ra1, dc1], in the sense north
               through east rotating about [ra1, dc1].  See U above 
               for units.

   PROCEDURE:
       The "four-parts formula" from spherical trig (p. 12 of Smart's
       Spherical Astronomy or p. 12 of Green' Spherical Astronomy).

   EXAMPLE:
       For the star 56 Per, the Hipparcos catalog gives a position of 
       RA = 66.15593384, Dec = 33.94988843 for component A, and 
       RA = 66.15646079, Dec =  33.96100069 for component B.   What is the
       position angle of B relative to A?

       IDL> RA1 = 66.15593384/15.d   & DC1 = 33.95988843
       IDL> RA2 = 66.15646079/15.d   & DC2 = 33.96100069
       IDL> posang,1,ra1,dc1,ra2,dc2, ang
            will give the answer of ang = 21.4 degrees
   NOTES:
       (1) If RA1,DC1 are scalars, and RA2,DC2 are vectors, then ANGLE is a
       vector giving the position angle between each element of RA2,DC2 and 
       RA1,DC1.   Similarly, if RA1,DC1 are vectors, and RA2, DC2 are scalars,
       then DIS is a vector giving the position angle of each element of RA1, 
       DC1 and RA2, DC2.    If both RA1,DC1 and RA2,DC2 are vectors then ANGLE 
       is a vector giving the position angle between each element of RA1,DC1 
       and the corresponding element of RA2,DC2.    If then vectors are not the
       same length, then excess elements of the longer one will be ignored.

       (2) Note that POSANG is not commutative -- the position angle between
        A and B is theta, then the position angle between B and A is 180+theta 
   PROCEDURE CALLS:
        ISARRAY()
   HISTORY:
       Modified from GCIRC, R. S. Hill, RSTX, 1 Apr. 1998
       Use V6.0 notation W.L. Mar 2011

(See $IDLUTILS_DIR/goddard/pro/astro/posang.pro)

POSITIVITY

 NAME:
	POSITIVITY
 PURPOSE:
	Map an image uniquely and smoothly into all positive values.
 EXPLANATION:
	Take unconstrained x (usually an image), and map it uniquely and 
	smoothly into positive values.   Negative values of x get mapped to 
	interval ( 0, sqrt( epsilon )/2 ], positive values go to 
	( sqrt( epsilon )/2, oo ) with deriv approaching 1.  Derivative is 
	always 1/2 at x=0.   Derivative is used by the MRL deconvolution 
	algorithm.

 CALLING SEQUENCE:
	result = POSITIVITY( x, [ /DERIVATIVE, EPSILON = )

 INPUTS:
	x - input array, unconstrained

 OUTPUT:
	result =  output array = ((x + sqrt(x^2 + epsilon))/2
		if the /DERIV keyword is set then instead the derivative of
		the above expression with respect to X is returned

 OPTIONAL INPUT KEYWORDS:
	DERIV -  if this keyword set, then the derivative of the positivity
		mapping is returned, rather than the mapping itself
	EPSILON - real scalar specifying the interval into which to map
		negative values.    If EPSILON EQ 0 then the mapping reduces to 
		positive truncation.   If EPSILON LT then the mapping reduces to
		an identity (no change).  Default is EPSILON = 1e-9 

 REVISION HISTORY:
	 F.Varosi NASA/GSFC 1992, as suggested by R.Pina UCSD.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/image/positivity.pro)

PRECESS

 NAME:
      PRECESS
 PURPOSE:
      Precess coordinates from EQUINOX1 to EQUINOX2.  
 EXPLANATION:
      For interactive display, one can use the procedure ASTRO which calls 
      PRECESS or use the /PRINT keyword.   The default (RA,DEC) system is 
      FK5 based on epoch J2000.0 but FK4 based on B1950.0 is available via 
      the /FK4 keyword.

      Use BPRECESS and JPRECESS to convert between FK4 and FK5 systems
 CALLING SEQUENCE:
      PRECESS, ra, dec, [ equinox1, equinox2, /PRINT, /FK4, /RADIAN ]

 INPUT - OUTPUT:
      RA - Input right ascension (scalar or vector) in DEGREES, unless the 
              /RADIAN keyword is set
      DEC - Input declination in DEGREES (scalar or vector), unless the 
              /RADIAN keyword is set
              
      The input RA and DEC are modified by PRECESS to give the 
      values after precession.

 OPTIONAL INPUTS:
      EQUINOX1 - Original equinox of coordinates, numeric scalar.  If 
               omitted, then PRECESS will query for EQUINOX1 and EQUINOX2.
      EQUINOX2 - Equinox of precessed coordinates.

 OPTIONAL INPUT KEYWORDS:
      /PRINT - If this keyword is set and non-zero, then the precessed
               coordinates are displayed at the terminal.    Cannot be used
               with the /RADIAN keyword
      /FK4   - If this keyword is set and non-zero, the FK4 (B1950.0) system
               will be used otherwise FK5 (J2000.0) will be used instead.
      /RADIAN - If this keyword is set and non-zero, then the input and 
               output RA and DEC vectors are in radians rather than degrees

 RESTRICTIONS:
       Accuracy of precession decreases for declination values near 90 
       degrees.  PRECESS should not be used more than 2.5 centuries from
       2000 on the FK5 system (1950.0 on the FK4 system).

 EXAMPLES:
       (1) The Pole Star has J2000.0 coordinates (2h, 31m, 46.3s, 
               89d 15' 50.6"); compute its coordinates at J1985.0

       IDL> precess, ten(2,31,46.3)*15, ten(89,15,50.6), 2000, 1985, /PRINT

               ====> 2h 16m 22.73s, 89d 11' 47.3"

       (2) Precess the B1950 coordinates of Eps Ind (RA = 21h 59m,33.053s,
       DEC = (-56d, 59', 33.053") to equinox B1975.

       IDL> ra = ten(21, 59, 33.053)*15
       IDL> dec = ten(-56, 59, 33.053)
       IDL> precess, ra, dec ,1950, 1975, /fk4

 PROCEDURE:
       Algorithm from Computational Spherical Astronomy by Taff (1983), 
       p. 24. (FK4). FK5 constants from "Astronomical Almanac Explanatory
       Supplement 1992, page 104 Table 3.211.1.

 PROCEDURE CALLED:
       Function PREMAT - computes precession matrix 

 REVISION HISTORY
       Written, Wayne Landsman, STI Corporation  August 1986
       Correct negative output RA values   February 1989
       Added /PRINT keyword      W. Landsman   November, 1991
       Provided FK5 (J2000.0)  I. Freedman   January 1994
       Precession Matrix computation now in PREMAT   W. Landsman June 1994
       Added /RADIAN keyword                         W. Landsman June 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Correct negative output RA values when /RADIAN used    March 1999 
       Work for arrays, not just vectors  W. Landsman    September 2003

(See $IDLUTILS_DIR/goddard/pro/astro/precess.pro)

PRECESS_CD

 NAME:
       PRECESS_CD

 PURPOSE:
       Precess the CD (coordinate description) matrix from a FITS header 
 EXPLANATION:
       The CD matrix is precessed from EPOCH1 to EPOCH2.  Called by HPRECESS

 CALLING SEQUENCE:
       PRECESS_CD, cd, epoch1, epoch2, crval_old, crval_new, [/FK4]  

 INPUTS/OUTPUT:
       CD - 2 x 2 CD (coordinate description) matrix in any units
               (degrees or radians).  CD will altered on output to contain 
               precessed values in the same units.    On output CD will always
               be double precision no matter how input.

 INPUTS:
       EPOCH1 - Original equinox of coordinates, scalar (e.g. 1950.0).  
       EPOCH2 - Equinox of precessed coordinates, scalar (e.g. 2000.0)
       CRVAL_OLD - 2 element vector containing RA and DEC in DEGREES
               of the reference pixel in the original equinox
       CRVAL_NEW - 2 elements vector giving CRVAL in the new equinox 

 INPUT KEYWORD:
       /FK4 - If this keyword is set, then the precession constants are taken
             in the FK4 reference frame.   The default is the FK5 frame.

 RESTRICTIONS:
       PRECESS_CD should not be used more than 2.5 centuries from the
       year 1900.      

 PROCEDURE:
       Adapted from the STSDAS program FMATPREC.  Precession changes the
       location of the north pole, and thus changes the rotation of
       an image from north up.  This is reflected in the precession of the
       CD matrix.   This is usually a very small change. 

 PROCEDURE CALLS:
       PRECESS

 REVISION HISTORY:
       Written, Wayne Landsman, ST Systems  February 1988
       Fixed sign error in computation of SINRA     March 1992
       Added /FK4 keyword                           Feb 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Use B/Jprecess for conversion between 1950 and 2000 W.L. Aug 2009

(See $IDLUTILS_DIR/goddard/pro/astro/precess_cd.pro)

PRECESS_XYZ

 NAME:
	PRECESS_XYZ

 PURPOSE:
	Precess equatorial geocentric rectangular coordinates. 

 CALLING SEQUENCE:
	precess_xyz, x, y, z, equinox1, equinox2

 INPUT/OUTPUT:
	x,y,z: scalars or vectors giving heliocentric rectangular coordinates
              THESE ARE CHANGED UPON RETURNING.
 INPUT:
	EQUINOX1: equinox of input coordinates, numeric scalar
       EQUINOX2: equinox of output coordinates, numeric scalar

 OUTPUT:
	x,y,z are changed upon return

 NOTES:
   The equatorial geocentric rectangular coords are converted
      to RA and Dec, precessed in the normal way, then changed
      back to x, y and z using unit vectors.

EXAMPLE:
	Precess 1950 equinox coords x, y and z to 2000.
	IDL> precess_xyz,x,y,z, 1950, 2000

HISTORY:
	Written by P. Plait/ACC March 24 1999 
	   (unit vectors provided by D. Lindler)
       Use /Radian call to PRECESS     W. Landsman     November 2000
       Use two parameter call to ATAN   W. Landsman    June 2001

(See $IDLUTILS_DIR/goddard/pro/astro/precess_xyz.pro)

PREMAT

 NAME:
       PREMAT
 PURPOSE:
       Return the precession matrix needed to go from EQUINOX1 to EQUINOX2.  
 EXPLANTION:
       This matrix is used by the procedures PRECESS and BARYVEL to precess 
       astronomical coordinates

 CALLING SEQUENCE:
       matrix = PREMAT( equinox1, equinox2, [ /FK4 ] )

 INPUTS:
       EQUINOX1 - Original equinox of coordinates, numeric scalar.  
       EQUINOX2 - Equinox of precessed coordinates.

 OUTPUT:
      matrix - double precision 3 x 3 precession matrix, used to precess
               equatorial rectangular coordinates

 OPTIONAL INPUT KEYWORDS:
       /FK4   - If this keyword is set, the FK4 (B1950.0) system precession
               angles are used to compute the precession matrix.   The 
               default is to use FK5 (J2000.0) precession angles

 EXAMPLES:
       Return the precession matrix from 1950.0 to 1975.0 in the FK4 system

       IDL> matrix = PREMAT( 1950.0, 1975.0, /FK4)

 PROCEDURE:
       FK4 constants from "Computational Spherical Astronomy" by Taff (1983), 
       p. 24. (FK4). FK5 constants from "Astronomical Almanac Explanatory
       Supplement 1992, page 104 Table 3.211.1.

 REVISION HISTORY
       Written, Wayne Landsman, HSTX Corporation, June 1994
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/premat.pro)

PRIME

 NAME:
     PRIME
 PURPOSE:
     Return an array with the specified number of prime numbers.
 EXPLANATATION:
     This procedure is similar to PRIMES in the standard IDL distribution,
     but stores results in a common block, and so is much faster 

 CALLING SEQUENCE:
       p = prime(n)
 INPUTS:
       n = desired number of primes, scalar positive integer
 OUTPUTS:
       p = resulting array of primes, vector of positive integers
 COMMON BLOCKS:
       prime_com
 NOTES:
       Note: Primes that have been found in previous calls are
         remembered and are not regenerated.
 MODIFICATION HISTORY:
       R. Sterner  17 Oct, 1985.
       R. Sterner,  5 Feb, 1993 --- fixed a bug that missed a few primes.
       Converted to IDL V5          March 1999

 Copyright (C) 1985, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.

(See $IDLUTILS_DIR/goddard/pro/jhuapl/prime.pro)

PRINT_STRUCT

 NAME:
       PRINT_STRUCT

 PURPOSE:
       Print the tag values of an array of structures in nice column format.
 EXPLANATION:
       The tag names are displayed in a header line.

 CALLING SEQUENCE:
       print_struct, structure, Tags_to_print [ , title, string_matrix 
                FILE=, LUN_OUT=, TNUMS= , TRANGE= , FRANGE=, WHICH=
                FORM_FLOAT =, MAX_ELEMENTS
 INPUTS:
       structure = array of structured variables

       Tags_to_print = string array specifying the names of tags to print.
                       Default is to print all tags which are not arrays.
 OPTIONAL INPUT KEYWORDS:
       FILE = string, optional file name to which output will then be written.
       LUN_OUT = Logical unit number for output to an open file,
               default is to print to standard output.
       TNUMS = tag numbers to print (alternative to specifying tag names).
       TRANGE = [beg,end] tag number range to print.
       FRANGE = same as TRANGE.
       WHICH = optional array of subscripts to select
               which structure elements to print.
       FORM_FLOAT = string array of three elements specifying
               floating point format, ex: FORM=['f','9','2'] means "(F9.2)",
               (default float format is G12.4).
       MAX_ELEMENTS = positive integer, print only tags that have less than
                       this number of elements (default is no screening).
       /NO_TITLE - If set, then the header line of tag names is not printed
       /STRINGS : instead of printing, return the array of strings in
               fourth argument of procedure: string_matrix.
 OUTPUTS:
       title = optional string, list of tags printed/processed.
       string_matrix = optional output of string matrix of tag values,
                       instead of printing to terminal or file, if /STRINGS.
 PROCEDURE:
       Check the types and lengths of fields to decide formats,
       then loop and form text string from requested fields, then print.
 HISTORY:
       Written: Frank Varosi NASA/GSFC 1991.
       F.V.1993, fixed up the print formats.
       F.V.1994, added more keyword options.
       F.V.1997, added WHICH and MAX_ELEM keyword options.
       WBL 1997, Use UNIQ() rather than UNIQUE function
       Remove call to N_STRUCT()   W. Landsman  March 2004
       Avoid overflow with more than 10000 elements  W. Landsman Nov 2005
       Really remove call to N_STRUCT() W. Landsman July 2009

(See $IDLUTILS_DIR/goddard/pro/structure/print_struct.pro)

PROB_KS

 NAME:
       PROB_KS
 PURPOSE:
       Return the significance of the Kolmogoroff-Smirnov statistic
 EXPLANATION:
       Returns the significance level of an observed value of the 
       Kolmogorov-Smirnov statistic D for an effective number of data points
       N_eff.   Called by KSONE and KSTWO

 CALLING SEQUENCE:
       prob_ks, D, N_eff, probks

 INPUT PARAMATERS:
       D -  Kolmogorov statistic, floating scalar, always non-negative
       N_eff - Effective number of data points, scalar.   For a 2 sided test 
               this is given by (N1*N2)/(N1+N2) where N1 and N2 are the number 
               of points in each data set.

 OUTPUT PARAMETERS:
       probks - floating scalar between 0 and 1 giving the significance level of
               the K-S statistic.   Small values of PROB suggest that the 
               distribution being tested are not the same

 REVISION HISTORY:
       Written     W. Landsman                August, 1992
       Corrected typo (termbv for termbf)    H. Ebeling/W.Landsman  March 1996
       Probably did not affect numeric result, but iteration went longer
       than necessary
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/prob_ks.pro)

PROB_KUIPER

 NAME:
       PROB_KUIPER
 PURPOSE:
       Return the significance of the Kuiper statistic
 EXPLANATION:
       Returns the significance level of an observed value of the
       Kuiper statistic D for an effective number of data points
       N_eff.   Called by KUIPERONE

 CALLING SEQUENCE:
       prob_kuiper, D, N_eff, probks

 INPUT PARAMATERS:
       D -  Kuiper statistic, floating scalar, always non-negative
       N_eff - Effective number of data points, scalar.   For a 2 sided test
               this is given by (N1*N2)/(N1+N2) where N1 and N2 are the number
               of points in each data set.

 OUTPUT PARAMETERS:
       probks - floating scalar between 0 and 1 giving the significance level of
               the Kuiper statistic.   Small values of PROB suggest that the
               distribution being tested are not the same

 REVISION HISTORY:
       Written     W. Landsman                August, 1992
       Corrected typo (termbv for termbf)    H. Ebeling/W.Landsman  March 1996
       Probably did not affect numeric result, but iteration went longer
       than necessary
       Converted to IDL V5.0   W. Landsman   September 1997
       Adapted from PROB_KS    J. Ballet     July 2003

(See $IDLUTILS_DIR/goddard/pro/math/prob_kuiper.pro)

PROGRAMROOTDIR

 NAME:
       ProgramRootDir

 PURPOSE:

       The purpose of this function is to provide a portable way of finding
       the root directory of a program distribution. The directory that is returned
       is the directory in which the source file using ProgramRootDir resides.
       The program is useful for distributing applications that have a large number
       of files in specific program directories.


 AUTHOR:

       FANNING SOFTWARE CONSULTING
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com

 SYNTAX:

       theDirectory = ProgramRootDir()

 RETURN_VALUE:

       theDirectory:   The directory in which the program module running ProgramRootDir resides.

 ARGUMENTS:

       None.

 KEYWORDS:

       NOMARK: Normally, the directory that is returned contains a path separator at its
               end, so that the directory can easily be concatinated with other file names.
               If this keyword is set, the final path separator mark is removed from the
               directory name.

       ONEUP:  Set this keyword if you want to start your search one directory
               *above* where your source program resides (i.e., "../Source").
               This allows you, for example, to put your source files in a Source
               directory that it at the same level as your Data directory, Utility
               directory, etc. See the example below.

       TWOUP:  Set this keyword if you want to start your search two directories
               *above* where your source program resides (i.e., "../../Source").


 EXAMPLE:

       Assume that your application files (and source programs) reside in this root directory:

           ../app

       You have placed a DATA directory immediately under the APP directiory, and a RESOURCES
       directory immedately under the DATA directory. Your directory structure looks like this:

           ../app                    ; Contains your application and source (*.pro) files.
           ../app/data               ; Contains your application data files.
           ...app/data/resources     ; Contains your application resource files.

       The end user can install the APP directory wherever he or she likes. In your
       program, you will identify the DATA and RESOURCES directory like this:

            ; Get icon image in resources directory.
            filename = Filepath(Root_Dir=ProgramRootDir(), Subdirectory=['data','resources'], 'myicon.tif')

            ; Get default image in data directory.
            filename = Filepath(Root_Dir=ProgramRootDir(), Subdirectory='data', 'ctscan.tif')

       Alternatively, you might set up an application directory structure like this:

           ../app                    ; Contains your application files.
           ../app/source             ; Contains your application source (*.pro) files.
           ../app/data               ; Contains your application data files.
           ...app/data/resources     ; Contains your application resource files.

       In this case, you would use the ONEUP keyword to find your data and resource files, like this:

            ; Get icon image in resources directory.
            filename = Filepath(Root_Dir=ProgramRootDir(/ONEUP), Subdirectory=['data','resources'], 'myicon.tif')

            ; Get default image in data directory.
            filename = Filepath(Root_Dir=ProgramRootDir(/ONEUP), Subdirectory='data', 'ctscan.tif')



 MODIFICATION_HISTORY:

       Written by: David W. Fanning, 23 November 2003. Based on program SOURCEROOT, written by
         Jim Pendleton at RSI (http://www.rsinc.com/codebank/search.aspx?FID=35).
       Added ONEUP keyword. 10 December 2003. DWF.
       Added TWOUP keyword. 8 June 2007. DWF.
       Added NOMARK keyword. 8 June 2007. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/programrootdir.pro)

PSCONFIG

The purpose of this program is to allow the user to configure the PostScript device
with or without a graphical user interface. This function is essentially a simplified
wrapper to the FSC_PSConfig object, which provides a powerful graphical user interface
for configuring the IDL PostScript device.

:Categories:
Utilities, Graphics

:Returns:
A structure of keywords, appropriate for configuring the PostScript device, is returned.
These keywords are generally passed to the PostScript device by means of keyword inheritance::

keywords = PSConfig() ; Obtain PostScript keywords
Set_Plot, 'PS' ; Select the PostScript device
Device, _Extra=keywords ; Configure the PostScript device with keywords

:Params:
psobject: in, optional, type=object
An FSC_PSCONFIG object reference of the sort returned by this function
can be passed as an argument to the function. It is up to the user to destroy
the object if passed as an argument. Passing an object argument essentially
by-passes the rest of the keywords and the GUI will take its initial values
from the values in the input object. This allows the programmer to keep track
of how the user last configured the GUI and to set it up in exactly the same
way the next time the GUI is invoked.

:Keywords:
AvantGarde: in, optional, type=boolean, default=0
Set this keyword to select the AvantGarde PostScript font.
Bits_per_Pixel: in, optional, type=integer, default=8
The number of image bits saved for each image pixel: 2, 4, or 8.
Bold: in, optional, type=boolean, default=0
Set this keyword to select a bold PostScript font.
BookStyle: in, optional, type=boolean, default=0
Set this keyword to specify that the book version of the current PostScript
font should be used.
Bkman: in, optional, type=boolean, default=0
Set this keyword to select the Bookman PostScript font.
Cancel: out, optional, type=boolean, default=0
If this keyword is set to 1, the user hit the Cancel button in the GUI.
CMYK: in, optional, type=boolean, default=0
Set this keyword to use CMYK colors instead of RGB colors in the output.
Color: in, optional, type=boolean, default=1
Set this keyword to 1 to select color or gray-scale output.
Courier: in, optional, type=boolean, default=0
Set this keyword to select the Courier font.
Debug: in, optional, type=boolean, default=0
Set this keyword to get traceback information when errors are encountered.
Decomposed: in, optional, type=boolean, default=0
Set this keyword to turn on 24-bit color support. Set to zero to select indexed color
support. Applies only to IDL versions 7.1 and higher.
DefaultSetup: in, optional, type=structure
Set this keyword to the "name" of a default style. Current styles (you can easily
create and add your own to the source code) are the following::
"System (Portrait)" - The normal "default" system set-up. Also, "System".
"System (Landcape)" - The normal "default" landscape system set-up.
"Centered (Portrait)" - The window centered on the page. Also, "Center" or "Centered".
"Centered (Landscape)" - The window centered on the landscape page. Also, "Landscape".
"Square (Portrait)" - A square plot, centered on the page.
"Square (Landscape)" - A square plot, centered on the landscape page.
"Figure (Small)" - A small encapsulated figure size, centered on page. Also, "Encapsulated" or "Encapsulate".
"Figure (Large)" - A larger encapsulated figure size, centered on page. Also, "Figure".
"Color (Portrait)" - A "centered" plot, with color turned on. Also, "Color".
"Color (Landscape)" - A "centered" landscape plot, with color turned on.
Demi: in, optional, type=boolean, default=0
Set this keyword to select the Demi font style.
Directory: in, optional, type=string
Set this keyword to the name of the starting directory. The current directory is used by default.
Encapsulated: in, optional, type=boolean, default=0
Set this keyword to 1 to select Encapsulated PostScript output.
European: in, optional
This keyword is depreciated in favor or `Metric`.
Filename: in, optional, type=string, default='idl.ps'
Set this keyword to the name of the PostScript file you wish to create.
FontInfo: in, optional, type=boolean, default=0
Set this keyword if you wish to see font information in the GUI interface. Since font
information has to be interpreted to be used, most users prefer not to see this information
on the GUI.
FontSize: in, optional, type=integer, default=12
Set this keyword to the desired font size. Values should be between 6 and 32.
FontType: out, optional, type=integer
This keyword is both an input and an output keyword. It allows you to specify the font
type you wish to use, and it also returns the font type the user selected in the GUI.
The user is responsibe for configuring the PostScript graphical commands with the appropriate font
type, because it cannot be done via the normal Device keyword channel. Normally, this is set to
!P.Font.
Group_Leader: in, optional, type=long
Set this keyword to the identifer of a widget group leader. This program will be destroyed
if the group leader application is destroyed.
Helvetica: in, optional, type=boolean, default=0
Set this keyword to select the Helvetica PostScript font.
Inches: in, optional, type=boolean, default=1
Set this keyword to indicate sizes and offsets are in inches as opposed to centimeters.
Set to zero by default if the `Metric` keyword is set.
Italic: in, optional, type=boolean, default=0
Set this keyword to select italic type font styling.
Isolatin: in, optional, type=boolean, default=0
Set this keyword to select ISOlatin1 encoding.
Landscape: in, optional, type=boolean, default=0
Set this keyword to select Landscape page output. Portrait page output is the default.
Light: in, optional, type=boolean, default=0
Set this keyword to select the Light PostScript style for the font.
Match: in, optional, type=boolean, default=0
If this keyword is set, the initial PostScript window will match the aspect ratio of the
current graphics window.
Medium: in, optional, type=boolean, default=0
Set this keyword to select the Medium PostScript style for the font.
Metric: in, optional, type=boolean, default=0
Set this keyword to indicate metric mode (i.e., A4 page and centimeter units).
Name: in, optional, type=string
Set this keyword to the "name" of the created FSC_PSConfig object.
Narrow: in, optional, type=boolean, default=0
Set this keyword to select the Narrow font style.
NoGUI: in, optional, type=boolean, default=0
Set this keyword if you don't want a graphical user interface, but just want to get the
return structure of keywords.
Oblique: in, optional, type=boolean, default=0
Set this keyword to select the Oblique font style.
PageType: in, optional, type=string, default='LETTER'
Set this keyword to the "type" of page. Possible values are::
"Letter" - 8.5 by 11 inches. (Default, unless the Metric keyword is set.)
"Legal" - 8.5 by 14 inches.
"Ledger" - 11 by 17 inches.
"A4" - 21.0 by 29.7 centimeters. (Default, if the Metric keyword is set.)
Palatino: in, optional, type=boolean, default=0
Set this keyword to select the Palatino font.
Preview: in, optional, type=integer, default=0
Set this keyword to select the type of PostScript preview to add to the file. Values 0, 1, or 2.
Adding previews to PostScript files created in IDL is not recommended as the results are always
poor. There are better methods to add PostScript previews using other software, such as GhostView.
Schoolbook: in, optional, type=boolean, default=0
Set this keyword to select the Schoolbook PostScript font.
Set_Font: in, optional, type=string
Set this keyword to the name of a PostScript hardware or true-type font you want to use.
Note that if you specify a true-type font, you must also set the `TrueType` keyword.
Symbol: in, optional, type=boolean, default=0
Set this keyword to select the Symbol PostScript font.
Times: in, optional, type=boolean, default=0
Set this keyword to select the Times PostScript font.
TrueType: in, optional, type=boolean, default=0
Set this keyword to use true-type fonts in the PostScript output. Set the name of the font
with the `Set_Font` keyword.
XOffset: in, optional, type=float
Set this keyword to the X Offset. Uses "System (Portrait)" defaults. (Note: offset
calculated from lower-left corner of page.)
XSize: in, optional, type=float
Set this keyword to the X size of the PostScript "window". Uses "System (Portrait)" defaults.
YOffset: in, optional, type=float
Set this keyword to the Y Offset. Uses "System (Portrait)" defaults. (Note: offset
calculated from lower-left corner of page.)
YSize: in, optional, type=float
Set this keyword to the Y size of the PostScript "window". Uses "System (Portrait)" defaults.
ZapfChancery: in, optional, type=boolean, default=0
Set this keyword to select the ZapfChancery PostScript font.
ZapfDingbats: in, optional, type=boolean, default=0
Set this keyword to select the ZapfDingbats PostScript font.

:Examples:
To have the user specify PostScript configuration parameters, use
the program like this::

keywords = PSConfig(Cancel=cancelled)
IF cancelled THEN RETURN
thisDevice = !D.Name
Set_Plot, 'PS'
Device, _Extra=keywords
Plot, findgen(11) ; Or whatever graphics commands you use.
Device, /Close_File
Set_Plot, thisDevice

:History:
Change History::
Written by David W. Fanning, 31 January 2000.
Added NOGUI keyword to allow default keywords to be obtained without
user interaction. 11 Oct 2004. DWF.
Added CMYK option 24 August 2007. Requires LANGUAGE_LEVEL=2 printer. L. Anderson
Updated for IDL 7.1 and 24-bt color PostScript support. 24 May 2009. DWF.
Added MATCH keyword. 14 Dec 2010. DWF.
Changed ENCAPSULATE keyword to ENCAPSULATED, which is what I always type! 29 Jan 2011. DWF.
Depreciated EUROPEAN keyword in favor of METRIC. 31 Jan 2011. DWF.

:Copyright:
Copyright (c) 2000-2012, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/psconfig.pro)

PSF_GAUSSIAN

 NAME:
       PSF_GAUSSIAN

 PURPOSE:
       Create a 1-d, 2-d, or 3-d Gaussian with specified FWHM, center 
 EXPLANATION:
       Return a point spread function having Gaussian profiles,
       as either a 1D vector, a 2D image, or 3D volumetric-data.

 CALLING SEQUENCE:
       psf = psf_Gaussian( NPIXEL=, FWHM= , CENTROID = 
                     [ /DOUBLE, /NORMALIZE, ST_DEV=,  NDIMEN= ] ) 
 or:
       psf = psf_Gaussian( parameters, NPIXEL = ,NDIMEN = )

 REQUIRED INPUT KEYWORD:
       NPIXEL = number pixels for each dimension, specify as an array,
               or just one number to make all sizes equal.

 OPTIONAL KEYWORDS:
       CENTROID = floating scalar or vector giving position of  PSF center.    
               default is exact center of requested vector/image/volume.
               The number of elements in CENTROID should equal the number of
               dimensions.    **The definition of Centroid was changed in
               March 2002, and now an integer defines the center of a pixel.**

       /DOUBLE  = If set, then the output array is computed in double precision
               the default is to return a floating point array.

       FWHM = the desired Full-Width Half-Max (pixels) in each dimension,
               specify as an array, or single number to make all the same.

       NDIMEN = integer dimension of result: either 1 (vector), 2 (image), or 
                3 (volume), default = 2 (an image result).

       /NORMALIZE causes resulting PSF to be normalized so Total( psf ) = 1.

       ST_DEV = optional way to specify width by standard deviation param.
                Ignored if FWHM is specified.

       XY_CORREL = scalar between 0 and 1 specifying correlation coefficient
               Use this keyword, for example, to specify an elliptical 
               Gaussian oriented at an angle to the X,Y axis.   Only valid
               for 2-dimensional case.


 INPUTS (optional):

       parameters = an NDIMEN by 3 array giving for each dimension:
                       [ maxval, center, st_dev ],  overrides other keywords.

 EXAMPLE:
       (1) Create a 31 x 31 array containing a normalized centered Gaussian 
       with an X FWHM = 4.3 and a Y FWHM = 3.6

       IDL> array = PSF_GAUSSIAN( Npixel=31, FWHM=[4.3,3.6], /NORMAL )

       (2) Create a 50 pixel 1-d Gaussian vector with a maximum of 12, 
          centered at  pixel 23 with a sigma of 19.2

       IDL> psf = psf_gaussian([12,23,19.2],npixel=50)
 EXTERNAL CALLS:
       function Gaussian()
 NOTES:
       To improve speed, floating underflow exceptions are suppressed (using 
       the MASK=32  keyword of CHECK_MATH() rather than being flagged.

 HISTORY:
       Written, Frank Varosi NASA/GSFC 1991.
       Converted to IDL V5.0   W. Landsman   September 1997
       Suppress underflow messages, add DOUBLE keyword. **Modified centroid
       definition so integer position is pixel center** W. Landsman March 2002
       Allow use of the ST_DEV (not STDEV) keyword W. Landsman Nov. 2002
       Do not modify NPIXEL input keyword   W. Landsman

(See $IDLUTILS_DIR/goddard/pro/image/psf_gaussian.pro)

PSWINDOW

NAME:
PSWINDOW

PURPOSE:

This function is used to calculate the size of a PostScript
window that has the same aspect ratio (ratio of height to
width) as the current display graphics window. It creates
the largest possible PostScript output window with the
desired aspect ratio. This assures that PostScript output
looks similar, if not identical, to normal graphics output
on the display.

AUTHOR:

CATEGORY:

Graphics.

CALLING SEQUENCE:

pageInfo = PSWINDOW()

INPUTS:

None.

KEYWORD PARAMETERS:

ASPECTRATIO: Normally the aspect ratio is matched to the
aspect ratio (ratio of height divided by width) of the current
graphics window. However, this keyword can be used to select
a particular aspect ratio for the PostScript window. This should
be a floating point value.

CM: Normally the structure value that is returned from this
function reports its values in inches. Setting this keyword
causes the return values to be in units of centimeters.

EUROPEAN: This keyword is depreciated in favor of METRIC.

FUDGE: A quick way to set symetrical XFUDGE and YFUDGE factors.
If this keyword is set to a value, XFUDGE and YFUDGE keywords are
set to the same value. Fudge factors are used only with some
printers and generally only when output is being sent to the
PRINTER device. (See the description of the XFUDGE and YFUDGE
keywords for additional information.)

LANDSCAPE: Normally, a landscape page is selected if the current
graphics window is wider than it is tall. If you prefer a landscape
aspect window on a Portrait page, set the LANDSCAPE keywword to 0.
Setting this keyword to 1 will result in a landscape page no
matter the size of the current graphics window.

MARGIN: The margin around the edges of the plot. The value must be
a floating point value between 0.0 and 0.35. It is expressed in
normalized coordinate units. The default margin is 0.05.

METRIC: If this keyword is set, the program defaults change
so that the CM keyword is set to 1 and the PAGESIZE keyword is
set to "A4".

PAGESIZE: Set this keyword to a string indicating the type
of PostScript page size you want. Current values are "LETTER",
"LEGAL", and "A4". Default is "LETTER".

PRINTER: Set this keyword if the output will be used to
configure the PRINTER device, rather than the PS device.
(In the PRINTER device, offsets are always calculated from
the lower-left corner of the page and do not rotate in
Landscape mode, as they do with the PS device.) Note that
the PRINTER device is only able to accept these keywords
in IDL 5.1 and higher.

XFUDGE: Printers calculate the offset point from the printable
edge of the paper (sometimes), rather from the corner of the paper.
For example, on my Lexmark printer, both X and Y offsets are
calculated from a point 0.25 inches in from the edge. This keyword
allows you to set a "fudge" factor that will be subtracted from
the XOFFSET that is returned to the user. This allows you to create
output that is centered on the page. The fudge factor should be in
the same units as the returned size and offset values.

YFUDGE: Printers calculate the offset point from the printable
edge of the paper (sometimes), rather from the corner of the paper.
For example, on my Lexmark printer, both X and Y offsets are
calculated from a point 0.25 inches in from the edge. This keyword
allows you to set a "fudge" factor that will be subtracted from
the YOFFSET that is returned to the user. This allows you to create
output that is centered on the page. The fudge factor should be in
the same units as the returned size and offset values.

OUTPUTS:

pageInfo: The output value is a named structure defined like
this:

pageInfo = {PSWINDOW_STRUCT, XSIZE:0.0, YSIZE:0.0, $
XOFSET:0.0, YOFFSET:0.0, INCHES:0, PORTRAIT:0, LANDSCAPE:0}

The units of the four size fields are inches unless the CM
keyword is set.

The output can be used to immediately configure the PostScript
or Printer device, like this:

Set_Plot, 'PS' ; or 'PRINTER'
Device, _Extra=pageInfo

RESTRICTIONS:

The aspect ratio of the current graphics window is calculated
like this:

aspectRatio = FLOAT(!D.Y_VSIZE) / !D.X_VSIZE

EXAMPLE:

To create a PostScript output window with the same aspect
ratio as the curently active display window, type:

pageInfo = PSWINDOW()
SET_PLOT, 'PS'
DEVICE, _Extra=pageInfo

To configure the PRINTER device:

pageInfo = PSWINDOW(/Printer, Fudge=0.25)
SET_PLOT, 'PRINTER'
DEVICE, _Extra=pageInfo

MODIFICATION HISTORY:

Written by: David W. Fanning, November 1996.
Fixed a bug in which the YOFFSET was calculated incorrectly
in Landscape mode. 12 Feb 97.
Took out a line of code that wasn't being used. 14 Mar 97.
Added correct units keyword to return structure. 29 JUN 98. DWF
Fixed a bug in how landscape offsets were calculated. 19 JUL 99. DWF.
Fixed a bug in the way margins were used to conform to my
original conception of the program. 19 JUL 99. DWF.
Added Landscape and Portrait fields to the return structure. 19 JUL 99. DWF.
Added PageSize keyword, changed MARGIN keyword, and completely
rewrote most of the intenal code. 9 FEB 2000. DWF.
Fixed a bug in how I calculated the aspect ratio. 1 MAR 2000. DWF.
Added PRINTER keyword to return proper offset values for the
PRINTER device, where the offset location is not rotated. 1 MAR 2000. DWF.
Added PRINTER fudge factors to take into account that printer offsets are
calculated from the printable area of the paper, rather than the corner
of the paper. 8 AUG 2000. DWF.
Changed the default margin to 0.05 from 0.15. 29 Nov 2004, DWF.
Added EUROPEAN keyword and set LANDSCAPE mode if window wider than higher
as the default if LANDSCAPE is not set. 13 Dec 2010. DWF.
Added ASPECTRATIO keyword to allow user-specified window aspect ratio. 13 Dec 2010. DWF.
Depreciated EUROPEAN keyword in favor of METRIC. 31 Jan 2011. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/pswindow.pro)

PS_BACKGROUND

 :Description:
   Provides a device-independent way to set the background color in the PostScript device.

 :Categories:
    Graphics, Utilities
    
 :Params:
    color: in, required, type=string/integer, default='white'
         The color that is used for the PostScript background. A polygon of
         this color is written to the PostScript file and fills the PostScript
         "window".
          
 :Examples:
       IDL> PS_Background, 'rose'
       
 :Author:
       FANNING SOFTWARE CONSULTING::
           David W. Fanning 
           1645 Sheely Drive
           Fort Collins, CO 80526 USA
           Phone: 970-221-0438
           E-mail: david@idlcoyote.com
           Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 :History:
     Change History::
        Written, 17 November 2010. DWF.
        Modified to use gcColorFill so that color is done with decomposed color. 24 Dec 2010. DWF.

 :Copyright:
     Copyright (c) 2010, Fanning Software Consulting, Inc.

(See $IDLUTILS_DIR/goddard/pro/coyote/ps_background.pro)

PS_END

The purpose of PS_START and PS_END is to make it easy to set-up
and close a PostScript file. These programs are used extensively
in all Coyote Graphics routines.

If `ImageMagick <http://www.imagemagick.org/script/index.php>` is installed
on your computer, you can easily convert PostScript output to GIF, JPEG, PNG, and TIFF
raster output. If `Ghostscript <http://www.ghostscript.com/download/>` is installed
you can convert PostScript output to PDF files. See the appropriate keywords below.

When PS_START is called, the current graphics device is set to "PS" (the PostScript
device). When PS_END is called the current graphics device is returned to the device
in effect when PS_START was called.

:Categories:
Utilities, Graphics

:Keywords:
allow_transparent: in, optional, type=boolean, default=0
To make the background of some image files white, rather than transparent,
you have to set the "-alpha off" string in the ImageMagick call. This
string is automatically added to the ImageMagick call unless this keyword
is set, in which case the string is not added and the image background will
be transparent.
bmp: in, optional, type=boolean, default=0
Set this keyword to convert the PostScript output file to a BMP image. Requires ImageMagick.
delete_ps: in, optional, type=boolean, default=0
Setting this keyword will delete the PostScript file that is used as the intermediate
file in the conversion to other file types.
density: in, optional, type=integer, default=300
The horizontal and vertical density (in dots per inch, DPI) of the image when the PostScript file
is converted to a raster format by ImageMagick.
gif: in, optional, type=boolean, default=0
Set this keyword to convert the PostScript output file to a GIF image. Requires ImageMagick.
gs_path: in, optional, type=string
This program assumes that UNIX users can access Ghostscript with the "gs"
command. It assumes WINDOWS users have installed Ghostscript in either
the C:\gs or C:\Program Files\gs directories. If either of these assumptions
is incorrect, you can specify the directory where the Ghostscript executable
resides with this keyword. (The Windows 32-bit executable is named gswin32c.exe
and the 64-bit executable is named gswin64c.exe.) Passed directly to cgPS2PDF.
im_options: in, optional, type=string, default=""
A string of ImageMagick "convert" options that can be passed to the ImageMagick convert
command. No error checking occurs with this string.
jpeg: in, optional, type=boolean, default=0
Set this keyword to convert the PostScript output file to a JPEG image. Requires ImageMagick.
nofix: in, optional, type=boolean, default=0
If this keyword is set, then the FixPS program to fix IDL landscape
PostScript files is not called.
nomessage: in, optional, type=boolean, default=0
If this keyword is set, then no error messages are issued. The keyword is used primarily
to allow PS_END to reset the internal structure without a lot of ruckus.
outfilename: out, optional, type=string
The name of the output filename created by the program.
pdf: in, optional, type=boolean, default=0
Set this keyword to convert the PostScript output file to a PDF file. Requires Ghostscript.
png: in, optional, type=boolean, default=0
Set this keyword to convert the PostScript output file to a PNG image. Requires ImageMagick.
Normally, 24-bit PNG files are created. However, if the IM_PNG8 keyword is set with
cgWindow_SetDefs, then PS_End will create an 8-bit PNG file instead.
resize: in, optional, type=integer, default=25
If an image is being created from the PostScript file, it is often resized by some
amount. You can use this keyword to change the value (e.g, RESIZE=100).
The value is passed on to resize argument as a percentage in the ImageMagick call.
showcmd: in, optional, type=boolean, default=0
Set this command to show the command used to do any PostScript coversions.
tiff: in, optional, type=boolean, default=0
Set this keyword to convert the PostScript output file to a TIFF image. Requires ImageMagick.
unix_convert_cmd: in, optional, type=string
There are a number of commands on UNIX machines for converting PostScript files
to PDF files. This program assumes you are using Ghostscript to do the conversion
for you. The Ghostscript command on most UNIX machines is "gs", which is used if
this keyword is undefined. However, if you would prefer to use another program to do
the conversion for you, you can specify the name of the command here. For example,
"pstopdf" or "epstopdf". In creating the actual command, this command will be
separated by a space from the input file name. In other words, if the alternative
conversion command was "pstopdf", the actual command would be "pstopdf" + " " + ps_file.
Any output filename is ignored. This command does not apply to Macintosh or Windows
computers. Passed directly to cgPS2PDF.
width: in, optional, type=integer
Set the keyword to the final pixel width of the output raster image. Applies
only to raster image file output (e.g., JPEG, PNG, TIFF, etc.). The height of
the image is chosen to preserve the image aspect ratio.

:Examples:
To create a line plot in a PostScript file named lineplot.ps and
also create a PNG file named lineplot.png for display in a browser,
type these commands::

PS_Start, FILENAME='lineplot.ps'
cgPlot, Findgen(11), COLOR='navy', /NODATA, XTITLE='Time', YTITLE='Signal'
cgPlot, Findgen(11), COLOR='indian red', /OVERPLOT
cgPlot, Findgen(11), COLOR='olive', PSYM=2, /OVERPLOT
PS_End, /PNG

:History:
Change History::
Written by: David W. Fanning, 20 May 2008.
Slight modification to allow filenames with spaces in them.
Added NoMatch keyword. 17 March 2009. DWF.
Added a number of keywords to make these commands more configurable. 19 March 2009. DWF.
Only set thickness system variables if starting system variables are set to their
default values (namely, 0). This allows users to set their own system variables
before they call PS_START, rather than after. 23 March 2009. DWF.
Moved PS_END to its own file to allow the IDLExBr_Assistant to work properly. 7 April 2009. DWF.
Reordered ImageMagick commands to put them in the proper sequence to get "alpha" switch to work. 23 April 2009. DWF.
Put the switches *ahead* of the PostScript file name. Now resizing works and default size reduction
returned to 25%. 23 April 2009. DWF.
Still having a devil of a time getting the ImageMagick "convert" command right. Fonts
have become a problem. Now trying a "flatten" option in the command. 12 May 2009. DWF.
If the PostScript file is in Landscape mode, it is now "fixed" with FixPS to allow it
to be displayed right-side up in PostScript viewers. 8 August 2009. DWF.
Fixed a problem in not checking the GIF keyword properly. 4 December 2009. DWF.
Added NOFIX keyword to the program. 1 November 2010. DWF.
Added better handing of errors coming from FIXPS after update to FIXPS. 15 November 2010. DWF.
Added DELETE_PS keyword. 16 Jan 2011. DWF.
Better protection of code from not finding ImageMagick. 17 Jan 2011. DWF.
Collecting result of SPAWN command. Only printing if QUIET=0. 16 Feb 2011. DWF.
Changes to handle inability to create raster files from PS encapsulated files in
landscape mode. Added NOMESSAGE keyword. 26 Aug 2011. DWF.
Added PDF keyword. Requires Ghostscript to use. 6 Dec 2011. DWF.
Added SHOWCMD keyword. 9 Dec 2011. DWF.
Added OUTFILENAME keyword. 11 Dec 2011. DWF.
Just realized a BMP case is missing from one of the CASE statements. 12 Dec 2011. DWF.
Added GS_PATH and UNIX_CONVERT_CMD keywords to support PDF output. 14 Dec 2011. DWF.
Add the WIDTH keyword. 3 April 2012. DWF.
Added a check for IM_PNG8 keyword, using cgWindow_GetDefs to see if an 8-bit or 24-bit
PNG file should be created. 3 April 2012. DWF.
Modified the ImageMagick commands that resizes the image to a particular width. Necessary
to accommodate PNG8 file output. Using ImageMagick 6.7.2-9. 4 April 2012. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/ps_end.pro)

PS_START

The purpose of PS_START and PS_END is to make it easy to set-up
and close a PostScript file. These programs are used extensively
in all Coyote Graphics routines.

PS_Start uses the current display window as a template for the Postscript
file. Thus, if the display window is wider than it is higher, output is
in Landscape mode. To set the size of the PostScript "window" yourself, be
sure to set the NOMATCH keyword to 1.

To display surface plots correctly the FONT keyword should be set to 1.
Otherwise, the default font is 0, or hardware fonts when outputting to
PostScript.

You can easily configure any modifications you like for your PostScript output
by setting fields in the plot and axis system variables (!P, !X, !Y, and !Z).
The modifications currently made by default in this program are these::

!P.Thick = 3
!P.CharThick = 3
!X.Thick = 3
!Y.Thick = 3
!Z.Thick = 3
!P.Font = 0

The !P.Charsize variable is set differently on Windows computers, and depending
on whether !P.MULTI is being used. On Windows the default is 1.25, or 1.00 for
multiple plots. On other computers, the default is 1.5, or 1.25 for multiple plots.
If true-type fonts are being used (FONT=1), the default is 1.5, or 1.25 for
multiple plots.

The PS_Start program contains the common block, _$FSC_PS_START_. See the FSC_PS_SETUP__DEFINE
program in the Coyote Library for its definition.

:Categories:
Utilities, Graphics

:Params:
filename: in, optional, type=string, default='idl.ps'
The name of the PostScript file created.

:Keywords:
cancel: out, optional, type=boolean, default=0
An output keyword that is set to 1 if the user cancelled from
PS_Config. Otherwise, set to 0.
charsize: in, optional, type=float
If this keyword is set, the !P.Charsize variable is set to this value until PS_END is called.
default_thickness: in, optional, type=integer, default=3
Sets the following system variables to this value while creating PostScript output:
!P.Thick, !P.CharThick, !X.Thick, !Y.Thick, !Z.Thick. These variables are returned to
their original values by `PS_End`. A system variable is set to this value only if it
currently contains the IDL default value of 0.0. If it is set to anything else, this
default thickness value is ignored.
filename: in, optional, type=string, default='idl.ps'
The name of the PostScript file created. An alternative, and older, way of setting
the `filename` parameter.
font: in, optional, type=integer, default=0
Set this to the type of font you want. A -1 selects Hershey fonts, a 0 selects hardware
fonts (Helvetica, normally), and a 1 selects a True-Type font. Set to 0 by default.
encapsulated: in, optional, type=boolean, default=0
Set this keyword to produce encapsulated PostScript output.
gui: in, optional, type=boolean, default=0
The default behavior is to use PSCONFIG to configure the PostScript device silently.
If you wish to allow the user to interatively configure the PostScript device, set this
keyword.
keywords: out, optional, type=structure
This output keyword contains the keyword structure returned from PS_Config.
landscape: in, optional, type=boolean, default=0
Set this keyword to produce landscape PostScript output.
nomatch: in, optional, type=boolean, default=0
Normally, PS_Start will try to "match" the aspect ratio of the PostScript file "window"
to the current display window. If this keyword is set, then this doesn't occur, giving
the user the option of specifying the size and offsets of the PostScript window directly
though appropriate keywords.
quiet: in, optional, type=boolean, default=0
If set, informational messages are not set.
scale_factor: in, optional, type=float, default=1.0
Set this to the PostScript scale factor. By default: 1.
tt_font: in, optional, type=string, default="Helvetica"
The name of a true-type font to use if FONT=1.
_ref_extra: in, optional
Any keyword appropriate for the PostScript configuration program PSConfig, from
the Coyote Library can be used with PS_Start.

:Examples:
To create a line plot in a PostScript file named lineplot.ps and
also create a PNG file named lineplot.png for display in a browser,
type these commands::

(See $IDLUTILS_DIR/goddard/pro/coyote/ps_start.pro)

PUTAST

 NAME:
    PUTAST
 PURPOSE:
    Put WCS astrometry parameters into a given FITS header.

 CALLING SEQUENCE:
     putast, hdr              ;Prompt for all values
               or
     putast, hdr, astr, [EQUINOX =, CD_TYPE =, ALT= , NAXIS=]
               or
     putast, hdr, cd,[ crpix, crval, ctype], [ EQUINOX =, CD_TYPE =, ALT= ]    

 INPUTS:
     HDR -  FITS header, string array.   HDR will be updated to contain
             the supplied astrometry.
     ASTR - IDL structure containing values of the astrometry parameters
            CDELT, CRPIX, CRVAL, CTYPE, LONGPOLE, and PV2
            See EXTAST.PRO for more info about the structure definition
                            or
     CD   - 2 x 2 array containing the astrometry parameters CD1_1 CD1_2
                                                             CD2_1 CD2_2
              in units of DEGREES/PIXEL
     CRPIX - 2 element vector giving X and Y coord of reference pixel
              BE SURE THE COORDINATES IN CRPIX ARE GIVEN IN FITS STANDARD
              (e.g. first pixel in image is [1,1] ) AND NOT IDL STANDARD
              (first pixel in image is [0,0]
     CRVAL - 2 element vector giving R.A. and DEC of reference pixel 
               in degrees
     CTYPE - 2 element string vector giving projection types for the two axes.
             For example, to specify a tangent projection one should set
             ctype = ['RA---TAN','DEC--TAN'] 

 OUTPUTS:
      HDR - FITS header now contains the updated astrometry parameters
               A brief HISTORY record is also added.

 OPTIONAL KEYWORD INPUTS:
       ALT -  single character 'A' through 'Z' or ' ' specifying an alternate 
              astrometry system to write in the FITS header.    The default is
              to write primary astrometry or ALT = ' '.   If /ALT is set, 
              then this is equivalent to ALT = 'A'.   See Section 3.3 of 
              Greisen & Calabretta (2002, A&A, 395, 1061) for information about
              alternate astrometry keywords.


       CD_TYPE - Integer scalar, either 0, 1 or 2 specifying how the CD matrix
                is to be written into the header
               (0) write PCn_m values along with CDELT values
               (1) convert to rotation and write as a CROTA2 value (+ CDELT)
               (2) as CDn_m values (IRAF standard) 

            All three forms are valid representations according to Greisen &
            Calabretta (2002, A&A, 395, 1061), also available at 
            http://fits.gsfc.nasa.gov/fits_wcs.html ) although form (0) is 
            preferred.   Form (1) is the former AIPS standard and is now  
            deprecated and cannot be used if any skew is present.
            If CD_TYPE is not supplied, PUTAST will try to determine the 
            type of astrometry already in the header.   If there is no 
            astrometry in the header then the default is CD_TYPE = 2.

      EQUINOX - numeric scalar giving the year of equinox  of the reference 
                coordinates.   Default (if EQUINOX keyword is not already
                present in header) is 2000.

      NAXIS - By default, PUTAST does not update the NAXIS keywords in the
            FITS header.    If NAXIS is set, and an astrometry structure is
            supplied then the NAXIS1 and NAXIS2 keywords in the FITS header 
            will be updated with the .NAXIS structure tags values.     If an 
            astrometry structure is not supplied, then one can set NAXIS to a 
            two element vector to update the NAXIS1, NAXIS2 keywords. 
 NOTES:
       The recommended use of this procedure is to supply an astrometry
       structure.    

       PUTAST does not delete astrometry parameters already present in the 
       header, unless they are explicity overwritten.   

       As of April 2012, PUTAST will add SIP 
      ( http://fits.gsfc.nasa.gov/registry/sip.html ) distortion parameters to
       a FITS header if present in the astrometry structure.  
 PROMPTS:
       If only a header is supplied, the user will be prompted for a plate 
       scale, the X and Y coordinates of a reference pixel, the RA and
       DEC of the reference pixel, the equinox of the RA and Dec and a 
       rotation angle.

 PROCEDURES USED:
       ADD_DISTORT, GETOPT(), GET_COORDS, GET_EQUINOX, SXADDPAR, SXPAR(), 
       TAG_EXIST(), ZPARCHECK
 REVISION HISTORY:
       Written by W. Landsman 9-3-87
       Major rewrite, use new astrometry structure   March, 1994
       Use both CD and CDELT to get plate scale for CD_TYPE=1   September 1995
       Use lower case for FITS keyword Comments  W.L.    March 1997
       Fixed for CD_TYPE=1 and CDELT = [1.0,1.0]   W.L   September 1997
       Default value of CD_TYPE is now 2, Use GET_COORDS to read coordinates
       to correct -0 problem           W.L.  September 1997
       Update CROTA1 if it already exists  W.L. October 1997
       Convert rotation to degrees for CD_TYPE = 1  W. L.   June 1998
       Accept CD_TYPE = 0 keyword input   W.L   October 1998
       Remove reference to obsolete !ERR  W.L.  February 2000
       No longer support CD001001 format, write default tangent CTYPE value
       consistent conversion between CROTA and CD matrix W.L. October 2000
       Use GET_EQUINOX to get equinox value  W.L.  January 2001
       Update CTYPE keyword if previous value is 'LINEAR'  W.L. July 2001
       Use SIZE(/TNAME) instead of DATATYPE()  W.L.   November 2001
       Allow direct specification of CTYPE W.L.        June 2002
       Don't assume celestial coordinates W. Landsman  April 2003
       Make default CD_TYPE = 2  W. Landsman   September 2003
       Add projection parameters, e.g. PV2_1, PV2_2 if present in the 
       input structure   W. Landsman    May 2004
       Correct interactive computation of image center W. Landsman Feb. 2005
       Don't use CROTA (CD_TYPE=1) if a skew exists W. Landsman  May 2005
       Added NAXIS keyword  W. Landsman   January 2007
       Update PC matrix, if CD_TYPE=0 and CD matrix supplied W.L. July 2007
       Don't write PV2 keywords for WCS types that don't use it W.L. Aug 2011
       Add SIP distortion parameters if present W.L. April 2012

(See $IDLUTILS_DIR/goddard/pro/astrom/putast.pro)

QDCB_GRID

 NAME:
	QDCB_GRID

 PURPOSE:
	Produce an overlay of latitude and longitude lines over a plot or image
 EXPLANATION:
	Grid is plotted on the current graphics device assuming that the 
	current plot is a map  in the so called quad cube projection. The 
	output plot range is assumed to go from 7.0 to -1.0 on the X axis and 
	-3.0 to 3.0 on the Y axis. Within this plotting space, the quad cube 
	faces are laid out as follows (X=Empty, Astronomical Layout shown - 
	X axis can be swapped for geographic maps):

	    3.0_
		XXX0
		4321
	   -3.0_XXX5
		|  |
	      7.0  -1.0

 CATEGORY:
	Mapping Support Routine

 CALLING SEQUENCE:

	QDCB_GRID,[,DLONG,DLAT,[LINESTYLE=N,/LABELS]

 INPUT PARAMETERS:

	DLONG	= Optional input longitude line spacing in degrees. If left
		  out, defaults to 30.

	DLAT    = Optional input lattitude line spacing in degrees. If left
		  out, defaults to 30.


 OPTIONAL KEYWORD PARAMETERS:

	LINESTYLE	= Optional input integer specifying the linestyle to
			  use for drawing the grid lines.

	LABELS		= Optional keyword specifying that the lattitude and
			  longitude lines on the prime meridian and the
			  equator should be labeled in degrees. If LABELS is
			  given a value of 2, i.e. LABELS=2, then the longitude
			  labels will be in hours and minutes instead of
			  degrees.

 OUTPUT PARAMETERS:

	NONE

 PROCEDURE:

	Uses WCSSPH2XY.PRO with projection 23 ("QSC" - COBE Quadrilatieralized
	Spherical Cube) to compute positions of grid lines and labels.

 COPYRIGHT NOTICE:

	Copyright 1991, The Regents of the University of California. This
	software was produced under U.S. Government contract (W-7405-ENG-36)
	by Los Alamos National Laboratory, which is operated by the
	University of California for the U.S. Department of Energy.
	The U.S. Government is licensed to use, reproduce, and distribute
	this software. Neither the Government nor the University makes
	any warranty, express or implied, or assumes any liability or
	responsibility for the use of this software.

 AUTHOR:

	Jeff Bloch

 MODIFICATIONS/REVISION LEVEL:

	%I%	%G%
	Use WCSSPH2XY instead of QDCB   Wayne Landsman   December 1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/qdcb_grid.pro)

QGET_STRING

 NAME:
     QGET_STRING
 PURPOSE:
     To get a string from the keyboard without echoing it to the screen.

 CALLING SEQUENCE:
     string = QGET_STRING() 

 INPUTS:
     None.

 OUTPUTS:
     string   The string read from the keyboard.

 SIDE EFFECTS:
     A string variable is created and filled.

 PROCEDURE:
     The IDL GET_KBRD functions is used to get each character in
     the string.  Each character is added to the string until a
     carriage return is struck.  The carriage return is not appended
     to the string.  Striking the delete key or the backspace key
     removes the previous character from the string.

 NOTES:
     For a widget password procedure see 
     http://idlcoyote.com/tip_examples/password.pro
 MODIFICATION HISTORY:
     Written by Michael R. Greason, STX, 8 January 1991.
     Work for Mac and Windows IDL  W. Landsman    September 1995

(See $IDLUTILS_DIR/goddard/pro/misc/qget_string.pro)

QSIMP

 NAME:
       QSIMP
 PURPOSE:
       Integrate using Simpson's rule to specified accuracy.
 EXPLANATION:
       Integrate a function to specified accuracy using the extended 
       trapezoidal rule.   Adapted from algorithm in Numerical Recipes, 
       by Press et al. (1992, 2nd edition), Section 4.2.     This procedure
       has been partly obsolete since IDL V3.5 with the introduction of the 
       intrinsic function QSIMP(), but see notes below.

 CALLING SEQUENCE:
       QSIMP, func, A, B, S, [ EPS = , MAX_ITER =, _EXTRA =  ]

 INPUTS:
       func - scalar string giving name of function of one variable to 
               be integrated
       A,B  - numeric scalars giving the lower and upper bound of the 
               integration

 OUTPUTS:
       S - Scalar giving the approximation to the integral of the specified
               function between A and B.

 OPTIONAL KEYWORD PARAMETERS:
       EPS - scalar specifying the fractional accuracy before ending the 
               iteration.  Default = 1E-6
       MAX_ITER - Integer specifying the total number iterations at which 
               QSIMP will terminate even if the specified accuracy has not yet
               been met.   The maximum number of function evaluations will be
               2^(MAX_ITER).    Default value is MAX_ITER = 20

       Any other keywords are passed directly to the user-supplied function
       via the _EXTRA facility.
 NOTES:
       (1) The function QTRAP is robust way of doing integrals that are not 
       very smooth.  However, if the function has a continuous 3rd derivative
       then QSIMP will likely be more efficient at performing the integral.

       (2) QSIMP can be *much* faster than the intrinsic QSIMP() function (as
       of IDL V7.1).   This is because the intrinsic QSIMP() function only 
       requires that the user supplied function accept a *scalar* variable.
       Thus on the the 16th iteration, the intrinsic QSIMP() makes 32,767
       calls to the user function, whereas this procedure makes one call 
       with a  32,767 element vector.  Also, unlike the intrinsic QSIMP(), this
       procedure allows keywords in the user-supplied function.

       (3) Since the intrinsic QSIMP() is a function, and this file contains a 
       procedure, there should be no name conflict.
 EXAMPLE:
       Compute the integral of sin(x) from 0 to !PI/3.
    
       IDL> QSIMP, 'sin', 0, !PI/3, S   & print, S
   
       The value obtained should be cos(!PI/3) = 0.5

 PROCEDURES CALLED:
       TRAPZD, ZPARCHECK

 REVISION HISTORY:
       W. Landsman         ST Systems Co.         August, 1991
       Continue after max iter warning message   W. Landsman   March, 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Pass keyword to function via _EXTRA facility  W. Landsman July 1999

(See $IDLUTILS_DIR/goddard/pro/math/qsimp.pro)

QTRAP

 NAME:
       QTRAP
 PURPOSE:
       Integrate using trapezoidal rule to specified accuracy.
 EXPLANATION:
       Integrate a function to specified accuracy using the extended 
       trapezoidal rule.   Adapted from Numerical Recipes (1992, 2nd edition),
       Section 4.2. 

 CALLING SEQUENCE:
       QTRAP, func, A, B, S, [EPS = , MAX_ITER =, _EXTRA = ]

 INPUTS:
       func - scalar string giving name of function of one variable to 
               be integrated
       A,B  - numeric scalars giving the lower and upper bound of the 
               integration

 OUTPUTS:
       S - Scalar giving the approximation to the integral of the specified
               function between A and B.

 OPTIONAL KEYWORD PARAMETERS:
       EPS - scalar specify the fractional accuracy before ending the 
             iteration.    Default = 1E-6
       MAX_ITER - Integer specifying the total number iterations at which 
               QTRAP will terminate even if the specified accuracy has not yet
               been met.    The maximum number of function evaluations will 
               be 2^(MAX_ITER).   Default value is MAX_ITER = 20

       Any other keywords are passed directly to the user-supplied function
       via the _EXTRA facility.
 NOTES:
       QTRAP is robust way of doing integrals that are not very smooth.  If the
       function has a continuous 3rd derivative then the function QSIMP will 
          likely be more efficient at performing the integral.
 EXAMPLE:
       Compute the integral of sin(x) from 0 to !PI/3.
    
       IDL> QTRAP, 'sin', 0, !PI/3, S   & print,S
   
       The value obtained should be cos(!PI/3) = 0.5

 PROCEDURES CALLED:
       TRAPZD, ZPARCHECK
 REVISION HISTORY:
       W. Landsman         ST Systems Co.         August, 1991
       Continue after Max Iter warning message, W. Landsman  March 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Pass keyword to function via _EXTRA facility  W. Landsman July 1999

(See $IDLUTILS_DIR/goddard/pro/math/qtrap.pro)

QUADTERP

 NAME:
       QUADTERP     
 PURPOSE:
       Quadratic interpolation of X,Y vectors onto a new X grid
 EXPLANATION:
       Interpolate a function Y = f(X) at specified grid points using an
       average of two neighboring 3 point quadratic (Lagrangian) interpolants.
       Use LINTERP for linear interpolation

 CALLING SEQUENCE:
       QUADTERP, Xtab, Ytab, Xint, Yint, [ MISSING = ]

 INPUT: 
       Xtab - Vector (X TABle) containing the current independent variable 
               Must be either monotonic increasing or decreasing
       Ytab - Vector (Y TABle) containing the dependent variable defined
               at each of the points of XTAB.
       Xint - Scalar or vector giving the values of X for which interpolated 
               Y values are sought

 OUTPUT: 
       Yint - Interpolated value(s) of Y, same number of points as Xint

 OPTIONAL INPUT KEYWORD:
       MISSING - Scalar specifying Yint value(s) to be assigned, when Xint
               value(s) are outside of the range of Xtab.     Default is to
               truncate the out of range Yint value(s) to the nearest value 
               of Ytab.   See the help for the INTERPOLATE function.
 METHOD:
       3-point Lagrangian interpolation.  The average of the two quadratics 
       derived from the four nearest  points is returned in YTAB.   A single
       quadratic is used near the end points.   VALUE_LOCATE is used 
       to locate center point of the interpolation.

 NOTES:
       QUADTERP provides one method of high-order interpolation.   The 
           RSI interpol.pro function includes the following alternatives:

       interpol(/LSQUADRATIC) - least squares quadratic fit to a 4 pt 
               neighborhood
       interpol(/QUADRATIC) - quadratic fit to a 3 pt neighborhood
       interpol(/SPLINE) - cubic spline fit to a 4 pt neighborhood

       Also, the IDL Astro function HERMITE fits a cubic polynomial and its
             derivative to the two nearest points. 
 RESTRICTIONS:
       Unless MISSING keyword is set, points outside the range of Xtab in 
       which valid quadratics can be computed are returned at the value 
       of the nearest end point of Ytab (i.e. Ytab[0] and Ytab[NPTS-1] ).

 EXAMPLE:
       A spectrum has been defined using a wavelength vector WAVE and a
       flux vector FLUX.  Interpolate onto a new wavelength grid, e.g. 

       IDL> wgrid = [1540.,1541.,1542.,1543.,1544.,1545.]
       IDL> quadterp, wave, flux, wgrid, fgrid 
     
       FGRID will be a 5 element vector containing the quadratically
       interpolated values of FLUX at the wavelengths given in WGRID.

  EXTERNAL ROUTINES:
       ZPARCHECK
  REVISION HISTORY:
       31 October 1986 by B. Boothman, adapted from the IUE RDAF
       12 December 1988 J. Murthy, corrected error in Xint
       September 1992, W. Landsman, fixed problem with double precision
       August 1993, W. Landsman, added MISSING keyword
       June, 1995, W. Landsman, use single quadratic near end points
       Converted to IDL V5.0   W. Landsman   September 1997
       Fix occasional problem with integer X table,  
       YINT is a scalar if XINT is a scalar   W. Landsman Dec 1999
       Use VALUE_LOCATE instead of TABINV W. Landsman  Feb. 2000

(See $IDLUTILS_DIR/goddard/pro/math/quadterp.pro)

QUERYDSS

 NAME: 
   QueryDSS

 PURPOSE: 
    Query the digital sky survey (DSS) on-line at  the STSCI (or ESO) server

 EXPLANATION: 
     The script can query the DSS survey and retrieve an image and FITS 
     header either from the the Space Telescope Science Institute (STScI) or 
     European Space Observatory (ESO) servers.
     See http://archive.eso.org/dss/dss and/or 
     http://archive.stsci.edu/dss/index.html for details.

 CALLING SEQUENCE: 
      QueryDSS, targetname_or_coords, Im, Hdr, [IMSIZE= , /ESO, Outfile= ]

 INPUTS:
      TARGETNAME_OR_COORDS - Either a scalar string giving a target name, 
          (with J2000 coordinates determined by SIMBAD (default) or NED), or 
          a 2-element numeric vector giving the J2000 right ascension in 
          *degrees* and the target declination in degrees.

 OPTIONAL INPUTS: 
          None

 OPTIONAL KEYWORD PARAMETERS: 
     ImSize - Numeric scalar giving size of the image to be retrieved in 
                 arcminutes.    Default is 10 arcminute.

     /ESO - Use the ESO server for image retrieval.    Default is to use
            the STScI server 

     /NED - Query the Nasa Extragalactic Database (NED) for the
            target's coordinates.  The default is to use Simbad for
            the target search.

     OUTPUT  - scalar string specifying name of output FITS file.    
            If set, then the output IDL variables are not used.
 
     /STSCI - obsolete keyword, now does nothing, since STSCI is the default
              Server.     

     SURVEY - Scalar string specifying which survey to retrieve.  
          Possible values are 
          '1' - First generation (red), this is the default
          '2b' - Second generation blue
          '2r' - Second generation red
          '2i' - Second generation near-infrared
 
      Note that 2nd generation images may not be available for all regions
      of the sky.   Also note that the first two letters of the 'REGION'
      keyword in the FITS header gives the bandpass 'XP' - Red IIIaF, 
      'XJ' - Blue IIIaJ, 'XF' - Near-IR IVN

      /VERBOSE - If set, then the query sent to the DSS server is displayed

 OUTPUTS: 
       Im - The image returned by the server. If there is an error, this 
             contains a single 0.

       Hdr - The FITS header of the image. Empty string in case of errors.

       If the OutFile keyword is set then no outputs are returned (only the
       file is written).
 SIDE EFFECTS: 
     If Im and Hdr exist in advance,  they are overwritten.

 RESTRICTIONS: 
      Relies on a working network connection. 

 PROCEDURE: 
      Construct a query-url,  call WEBGET() and sort out the server's 
      answer.

 EXAMPLE:           
      Retrieve an 10'  image surrounding the ultracompact HII region
       G45.45+0.06.   Obtain the 2nd generation blue image.

       IDL> QueryDSS, 'GAL045.45+00.06', image, header, survey = '2b'
       IDL> tvscl, image
       IDL> hprint, header
       IDL> writefits,'dss_image.fits', image, header
 Note that the coordinates could have been specified directly, rather than
 giving the target name.
       IDL> QueryDSS, [288.587, 11.1510], image, header,survey='2b'

 To write a file directly to disk, use the OutFile keyword

       IDL> QueryDSS, [288.587, 11.1510], survey='2b', out='gal045_2b.fits'
   
 PROCEDURES CALLED:
       QUERYSIMBAD, WEBGET()
 MODIFICATION HISTORY: 
       Written by M. Feldt, Heidelberg, Oct 2001 <mfeldt@mpia.de>
       Option to supply target name instead of coords  W. Landsman Aug. 2002
       Added OUTFILE, /NED keywords W. Landsman   April 2003
       Don't abort on Simbad failure W. Landsman/J. Brauher  June 2003
       Added /VERBOSE keyword W. Landsman   Jan 2009
       Make /STScI server the default  W. Landsman June 2010
      Fix OUTPUT option  W. Landsman June 2010

(See $IDLUTILS_DIR/goddard/pro/sockets/querydss.pro)

QUERYGSC

 NAME: 
   QUERYGSC

 PURPOSE: 
   Query the Guide Star Catalog (GSC V2.3.2) at STScI by position
 
 EXPLANATION:
   Uses the IDL SOCKET command to query the GSC 2.3.2 database over the Web.    

   Alternatively, (and more reliably) one can query the GSC 2.3.2 catalog using
   queryvizier.pro and the VIZIER database, e.g.  
     IDL> st = queryvizier('GSC2.3',[23,35],10,/all)
 
   GSC2.3 is an all-sky export of calibrated photographic survey plate 
   source parameters from the COMPASS database.  The number of unique
   objects is approximately 945,592,683.   All sources are 
   from the second-generation plate-processing pipeline with the exception
   of Tycho-2 and Skymap sources in the case of very bright objects. The 
   Skymap sources are exported when there is no matching GSC or Tycho 
   sources.  Each GSC 2.3 entry contains only one position and one 
   magnitude per bandpass for each unique sky object

 CALLING SEQUENCE: 
     info = QueryGSC(targetname_or_coords, [ dis, /HOURS] )

 INPUTS: 
      TARGETNAME_OR_COORDS - Either a scalar string giving a target name, 
          (with J2000 coordinates determined by SIMBAD), or a 2-element
          numeric vector giving the J2000 right ascension in *degrees* (or 
          hours if /HOURS is set) and the target declination in degrees.

 OPTIONAL INPUT:
    dis - Numeric scalar giving search radius in arcminutes to search around 
          specified target    Default is 5 arcminutes

 OPTIONAL INPUT KEYWORDS:

    /BOX - if set, then radius gives  a box width in arcminutes
    /HOURS - If set, then the right ascension is both input and output (in
             the info .ra tag) in hours instead of degrees
    /VERBOSE - If set, then the CGI command to the Webserver will be displayed
;
 OUTPUTS: 
   info - IDL structure containing information on the GSC stars within the 
          specified distance of the specified center.   There are (currently)
          23 tags in this structure  -- for further information see
          http://gsss.stsci.edu/Catalogs/GSC/GSC2/gsc23/gsc23_release_notes.htm

          .HSTID - GSC 2.3 name for HST operations
          .GSC1ID - GSC1 name
          .RA,.DEC - Position in degrees (double precision).   RA is given in
                   hours if the /HOURS keyword is set.
          .RAERR, .DECERR - uncertainty (in arcseconds) in the RA and Dec
          .EPOCH - mean epoch of the observation
          .FPGMAG, .FPGERR - magnitude and error in photographic F
          .JPGMAG, .JPGERR - magnitude and error in photographic J
          .VPGMAG, .VPGERR - V magnitude and error 
          .NPGMAG, .NPGERR - magnitude and error
          .UMAG, .UERR - magnitude and error
          .BMAG, .BERR - magnitude and error
          .VMAG, .VERR - magnitude and error
          .RMAG, .RERR - magnitude and error
          .IMAG, .IERR - magnitude and error
          .JMAG, .JERR - magnitude and error
          .HMAG, .HERR - magnitude and error
          .KMAG, .KERR - magnitude and error
          .A - semi-major axis in pixels
          .PA - Position angle of extended objects in degrees
          .E - eccentricity of extended objects
          .CLASS - classification (0-5): 0-star, 1-galaxy, 2-blend, 
                         3-nonstar, 4-unclassified, 5-defect
          .STATUS -10 digit field  used to encode more detailed information 
              about the properties of the catalog object.   For more info, see
http://www-gsss.stsci.edu/Catalogs/GSC/GSC2/gsc23/gsc23_release_notes.htm#ClassificationCodes
           .VFLAG, MFLAG - Variability nad multiplicity flags
            .FPGBAND, .NPGBAND, .JPGBAND. UBAND, BBAND, .VBAND - flag as 
            to wether given bandpass is available
 EXAMPLE: 
          Plot a histogram of the photographic J magnitudes of all GSC 2.3.2 
          stars within 10 arcminutes of the center of the globular cluster M13 

          IDL> info = querygsc('M13',10)
          IDL> plothist,info.jpgmag,xran=[10,20]

 PROCEDURES USED:
          QUERYSIMBAD, RADEC, WEBGET()

 MODIFICATION HISTORY: 
         Written by W. Landsman  SSAI  August 2002
         Fixed parsing of RA and Dec  W. Landsman September 2002
         Major rewrite to use new STScI Web server, remove magrange
           keyword   W. Landsman Dec 2007
         Update server name, added /BOX,/ VERBOSE keywords W.L 19 Dec 2007
         Web server now also returns infrared data  W.L. Feb 2010
         Fixed case where dec neg. and deg or min 0 Pat Fry Jul 2010

(See $IDLUTILS_DIR/goddard/pro/sockets/querygsc.pro)

QUERYSIMBAD

 NAME: 
   QUERYSIMBAD

 PURPOSE: 
   Query the SIMBAD/NED/Vizier astronomical name resolver to obtain coordinates

 EXPLANATION: 
   Uses the IDL SOCKET command to query either the SIMBAD or NED nameserver 
   over the Web to return J2000 coordinates.     ;   By default, QuerySimbad 
   first queries the Simbad database, then (if no match found) the NED 
   database, and then the Vizier database.
    
   For details on the SIMBAD service, see http://simbad.u-strasbg.fr/Simbad 
   and for the NED service, see http://ned.ipac.caltech.edu/

 CALLING SEQUENCE: 
    QuerySimbad, name, ra, dec, [ id, Found=, /NED, /CADC, ERRMSG=, /VERBOSE]

 INPUTS: 
    name - a scalar string containing the target name in SIMBAD (or NED)
           nomenclature. For SIMBAD details see
           http://vizier.u-strasbg.fr/cgi-bin/Dic-Simbad .

 OUTPUTS: 
     ra -  Right ascension of the target in J2000.0 in *degrees*, scalar 
     dec - declination of the target in degrees, scalar

 OPTIONAL INPUT KEYWORD:
     /CFA - if set, then use the Simbad server at the Center for Astrophysics
             rather than the default server in Strasbourg, France.
     ERRMSG   = If defined and passed, then any error messages will be
                  returned to the user in this parameter rather than
                  depending on the MESSAGE routine in IDL.  If no errors are
                  encountered, then a null string is returned. 
     /NED - if set, then only the nameserver of the NASA Extragalactic database
            is used to resolve the name and return coordinates.   Note that
           /NED cannot be used with Galactic objects
     /VERBOSE - If set, then the HTTP-GET command is displayed
     /PRINT - if set, then output coordinates are displayed at the terminal 
            By default, the coordinates are displayed if no output parameters
           are supplied to QUERYSIMBAD
     /SILENT - If set, then don't print warnings if multiple SIMBAD objects
             correspond to the supplied name.
 OPTIONAL OUTPUT: 
     id - the primary SIMBAD (or NED) ID of the target, scalar string
          As of June 2009, a more reliable ID seems to be found when using 
          CFA (/CFA) server.

 OPTIONAL KEYWORD OUTPUT:
     found - set to 1 if the translation was successful, or to 0 if the
           the object name could not be translated by SIMBAD or NED
     Errmsg - if supplied, then any error messages are returned in this
            keyword, rather than being printed at the terminal.   May be either
            a scalar or array.
     Server - Character indicating which server was actually used to resolve
           the object, 'S'imbad, 'N'ed or 'V'izier
            
 EXAMPLES:
     (1) Display the J2000 coordinates for the ultracompact HII region
         G45.45+0.06 

      IDL> QuerySimbad,'GAL045.45+00.06'
           ===>19 14 20.77  +11 09  3.6
 PROCEDURES USED:
       REPSTR(), WEBGET()

 NOTES:
     The actual  query is made to the Sesame name resolver 
     ( see http://cdsweb.u-strasbg.fr/doc/sesame.htx ).     The Sesame
     resolver first searches the Simbad name resolver, then  NED and then
     Vizier.   
 MODIFICATION HISTORY: 
     Written by M. Feldt, Heidelberg, Oct 2001   <mfeldt@mpia.de>
     Minor updates, W. Landsman   August 2002
     Added option to use NED server, better parsing of SIMBAD names such as 
          IRAS F10190+5349    W. Landsman  March 2003
     Turn off extended name search for NED server, fix negative declination
     with /NED    W. Landsman  April 2003
     Use Simbad Sesame sever, add /Verbose, /CADC keywords 
       B. Stecklum, TLS Tautenburg/ W. Landsman, Feb 2007
    Update NED query to account for new IPAC format, A. Barth  March 2007
    Update NED query to account for another new IPAC format, A. Barth  
                                                   July 2007
     Update message when NED does not find object  W.L.  October 2008
     Remove CADC keyword, add CFA keyword, warning if more than two
         matches  W.L. November 2008 
     Make NED queries through the Sesame server, add Server output 
          keyword  W.L.  June 2009
     Don't get primary name if user didn't ask for it  W.L. Aug 2009
     Added /SILENT keyword W.L. Oct 2009
     Added /PRINT keyword W.L.   Oct 2011

(See $IDLUTILS_DIR/goddard/pro/sockets/querysimbad.pro)

QUERYVIZIER

 NAME: 
   QUERYVIZIER

 PURPOSE: 
   Query any catalog in the Vizier database by position
 
 EXPLANATION:
   Uses the IDL SOCKET command to provide a positional query of any catalog 
   in the the Vizier (http://vizier.u-strasbg.fr/) database over the Web and
   return results in an IDL structure.    
 
    
 CALLING SEQUENCE: 
     info = QueryVizier(catalog, targetname_or_coords, [ dis
                        /ALLCOLUMNS, /CANADA, CONSTRAINT= ,/VERBOSE ])

 INPUTS: 
      CATALOG - Scalar string giving the name of the VIZIER catalog to be
            searched.    The complete list of catalog names is available at
            http://vizier.u-strasbg.fr/vizier/cats/U.htx . 

            Popular VIZIER catalogs include  
            'II/294' - Sloan SDSS photometric catalog Release 7 (2009)
            '2MASS-PSC' - 2MASS point source catalog (2003)
            'GSC2.3' - Version 2.3.2 of the HST Guide Star Catalog (2006)
            'USNO-B1' - Verson B1 of the US Naval Observatory catalog (2003)
            'NVSS'  - NRAO VLA Sky Survey (1998)
            'B/DENIS/DENIS' - 2nd Deep Near Infrared Survey of southern Sky
            'I/259/TYC2' - Tycho-2 main catalog (2000)
            'I/311/HIP2' - Hipparcos main catalog, new reduction (2007)

          Note that some names will prompt a search of multiple catalogs
          and QUERYVIZIER will only return the result of the first search.
          Thus, setting catalog to "HIP2" will search all catalogs 
          associated with the Hipparcos mission, and return results for the
          first catalog found.    To specifically search the Hipparcos or
          Tycho main catalogs use the VIZIER catalog names listed above
                             
      TARGETNAME_OR_COORDS - Either a scalar string giving a target name, 
          (with J2000 coordinates determined by SIMBAD), or a 2-element
          numeric vector giving the J2000 right ascension in *degrees* and 
          the target declination in degrees.
          If the targetname is set to 'NONE' then QUERYVIZIER will perform
          an all-sky search using the constraints given in the CONSTRAINT
          keyword.   
 OPTIONAL INPUT:
    dis - scalar or 2-element vector.   If one value is supplied then this
          is the search radius in arcminutes.     If two values are supplied
          then this is the width (i.e., in longitude direction) and height
          of the search box.   Default is a radius search with radius of
          5 arcminutes

 OUTPUTS: 
   info - Anonymous IDL structure containing information on the catalog  
          sources within the specified distance of the specified center.  The 
          structure tag names are identical with the VIZIER  catalog column 
          names, with the exception of an occasional underscore
          addition, if necessary to convert the column name to a valid 
          structure tag.    The VIZIER Web  page should consulted for the 
          column names and their meaning for each particular catalog..
           
          If the tagname is numeric and the catalog field is blank then either
          NaN  (if floating) or -1 (if integer) is placed in the tag.

          If no sources are found within the specified radius, or an
          error occurs in the query then -1 is returned. 
 OPTIONAL KEYWORDS:
          /ALLCOLUMNS - if set, then all columns for the catalog are returned
                 The default is to return a smaller VIZIER default set. 

          /CANADA - By default, the query is sent to the main VIZIER site in
            Strasbourg, France.   If /CANADA is set then the VIZIER site
            at the Canadian Astronomical Data Center (CADC) is used instead.
            Note that not all Vizier sites have the option to return
            tab-separated values (TSV) which is required by this program.
   
          CONSTRAINT - string giving additional nonpositional numeric 
            constraints on the entries to be selected.     For example, when 
            in the GSC2.3  catalog, to only select sources with Rmag < 16 set 
            Constraint = 'Rmag<16'.    Multiple constraints can be 
            separated by commas.    Use '!=' for "not equal", '<=' for smaller
            or equal, ">=" for greater than or equal.  See the complete list
            of operators at  
                 http://vizier.u-strasbg.fr/doc/asu.html#AnnexQual
            For this keyword only, **THE COLUMN NAME IS CASE SENSITIVE** and 
            must be written exactly as displayed on the VIZIER Web page.  
            Thus for the GSC2.3 catalog one must use 'Rmag' and not 'rmag' or
            'RMAG'.    In addition, *DO NOT INCLUDE ANY BLANK SPACE* unless it 
            is a necessary part of the query.
         
           /SILENT - If set, then no message will be displayed if no sources
                are found.    Error messages are still displayed.
           /VERBOSE - If set then the query sent to the VIZIER site is
               displayed, along with the returned title(s) of found catalog(s)
 EXAMPLES: 
          (1) Plot a histogram of the J magnitudes of all 2MASS point sources 
          stars within 10 arcminutes of the center of the globular cluster M13 

          IDL>  info = queryvizier('2MASS-PSC','m13',10)
          IDL> plothist,info.jmag,xran=[10,20]

          (2)  Find the brightest R magnitude GSC2.3 source within 3' of the 
               J2000 position ra = 10:12:34, dec = -23:34:35
          
          IDL> str = queryvizier('GSC2.3',[ten(10,12,34)*15,ten(-23,34,35)],3)
          IDL> print,min(str.rmag,/NAN)

          (3) Find sources with V < 19 in the Magellanic Clouds Photometric 
              Survey (Zaritsky+, 2002) within 5 arc minutes of  the position 
              00:47:34 -73:06:27

              Checking the VIZIER Web page we find that this catalog is
          IDL>  catname =  'J/AJ/123/855/table1'
          IDL>  ra = ten(0,47,34)*15 & dec = ten(-73,6,27)
          IDL> str = queryvizier(catname, [ra,dec], 5, constra='Vmag<19')

          (4) Perform an all-sky search of the Tycho-2 catalog for stars with
              BTmag = 13+/-0.1

         IDL> str = queryvizier('I/259/TYC2','NONE',constrain='BTmag=13+/-0.1')

 PROCEDURES USED:
          GETTOK(), REMCHAR, REPSTR(), STRCOMPRESS2(), WEBGET()
 TO DO:
       (1) Allow specification of output sorting
 MODIFICATION HISTORY: 
         Written by W. Landsman  SSAI  October 2003
         Give structure name returned by VIZIER not that given by user
                    W. Landsman   February 2004 
         Don't assume same format for all found sources W. L. March 2004
         Added CONSTRAINT keyword for non-positional constraints WL July 2004
         Remove use of EXECUTE() statement WL June 2005
         Make dis optional as advertised WL August 2005
         Update for change in Vizier output format WL February 2006
         Fix problem in Feb 2006 update when only 1 object found
                     WL/D.Apai        March 2006
         Accept 'E' format for floating point. M. Perrin April 2006
         Added /ALLCOLUMNS option to return even more data.  M. Perrin, May 2006
         Return anonymous structure W. Landsman  May 2006
         Removed V6.0 notation to restore V5 compatibility W.Landsman July2006
         Accept target='NONE' for all-sky search, allow '+/-' constraints
                W. Landsman  October 2006
         Use HTTP 1.0 protocol in call to webget.pro
         Use vector form of IDL_VALIDNAME if V6.4 or later W.L. Dec 2007
         Update Strasbourg Web address for target name W.L. 3 March 2008
         Also update Web address for coordinate search W.L. 7 March 2008 
         Allow for 'D' specification format  R. Gutermuth/W.L.  June 2008
         Allow for possible lower-case returned formats  W.L. July 2008
         Use STRCOMPRESS2()to remove blanks around operators in constraint
              string  W.L.  August 2008
         Added /SILENT keyword  W.L.  Jan 2009
         Avoid error if output columns but not data returned W.L. Mar 2010
         Ignore vector tags (e.g. SED spectra) W.L.   April 2011

(See $IDLUTILS_DIR/goddard/pro/sockets/queryvizier.pro)

RADEC

 NAME:
	RADEC
 PURPOSE:
	To convert RA and Dec  from decimal to sexigesimal units.
 EXPLANATION: 
	The conversion is to sexigesimal hours for RA,  and sexigesimal 
	degrees for declination.

 CALLING SEQUENCE:
	radec, ra, dec, ihr, imin, xsec, ideg, imn, xsc, [/HOURS}

 INPUTS:
	ra   - right ascension, scalar or vector, in DEGREES unless the
              /HOURS keyword is set
	dec  - declination in decimal DEGREES, scalar or vector, same number
		of elements as RA

 OUTPUTS:
	ihr  - right ascension hours   (INTEGER*2)
	imin - right ascension minutes (INTEGER*2)
	xsec - right ascension seconds  (REAL*4 or REAL*8)
	ideg - declination degrees (INTEGER*2)
	imn  - declination minutes (INTEGER*2)
	xsc  - declination seconds (REAL*4 or REAL*8)

 OPTIONAL KEYWORD INPUT:
       /HOURS - if set, then the input righ ascension should be specified in
              hours instead of degrees.
 RESTRICTIONS:
	RADEC does minimal parameter checking.

 REVISON HISTORY:
	Written by B. Pfarr, STX, 4/24/87
	Converted to IDL V5.0   W. Landsman   September 1997
       Added /HOURS keyword W. Landsman  August 2002

(See $IDLUTILS_DIR/goddard/pro/astro/radec.pro)

RANDOMCHI

   NAME:
      RANDOMCHI
 PURPOSE:
      GENERATE CHI-SQUARE DISTRIBUTED RANDOM VARIABLES.

 AUTHOR : BRANDON C. KELLY, STEWARD OBS., SEP 2005

 INPUTS :

   SEED - THE SEED FOR THE RANDOM NUMBER GENERATOR, CAN BE UNDEFINED.
   DOF - THE DEGREES OF FREEDOM FOR THE CHI-SQUARED DISTRIBUTION.

 OPTIONAL INPUTS :

   NRAND - THE NUMBER OF RANDOM NUMBERS TO DRAW

(See $IDLUTILS_DIR/goddard/pro/math/randomchi.pro)

RANDOMDIR

  NAME:
     RANDOMDIR
 PURPOSE:
     GENERATE DIRICHLET-DISTRIBUTED RANDOM VARIABLES.

 AUTHOR : BRANDON C. KELLY, STEWARD OBS., APRIL 2006

 INPUTS :

   SEED - THE SEED FOR THE RANDOM NUMBER GENERATOR, CAN BE UNDEFINED.
   ALPHA - THE SHAPE PARAMETERS FOR THE DIRICHLET DISTRIBUTION. THIS
           SHOULD BE A K-ELEMENT VECTOR.

 OPTIONAL INPUTS :

   NRAND - THE NUMBER OF RANDOM NUMBERS TO DRAW

 CALLED ROUTINES :

   RANDOMGAM

(See $IDLUTILS_DIR/goddard/pro/math/randomdir.pro)

RANDOMGAM

 NAME:
     RANDOMGAM
 PURPOSE:
     GENERATE GAMMA-DISTRIBUTED RANDOM VARIABLES.

 AUTHOR : BRANDON C. KELLY, STEWARD OBS., APRIL 2006

 INPUTS :

   SEED - THE SEED FOR THE RANDOM NUMBER GENERATOR, CAN BE UNDEFINED.
   ALPHA, BETA - THE SHAPE PARAMETERS FOR THE GAMMA DISTRIBUTION.

 OPTIONAL INPUTS :

   NRAND - THE NUMBER OF RANDOM NUMBERS TO DRAW

(See $IDLUTILS_DIR/goddard/pro/math/randomgam.pro)

RANDOMP

 NAME:
       RANDOMP
 PURPOSE:
       Generates an array of random numbers distributed as a power law.
 CALLING SEQUENCE:
       RANDOMP, X, Pow, N, [ RANGE_X = [low,high], SEED= ]'
 INPUTS:
       Pow:  Exponent of power law.
               The pdf of X is f_X(x) = A*x^pow, low <= x <= high
               ASTRONOMERS PLEASE NOTE:  
               pow is little gamma  = big gamma - 1 for stellar IMFs.
       N:    Number of elements in generated vector.

 OPTIONAL INPUT KEYWORD PARAMETER:
       RANGE_X:  2-element vector [low,high] specifying the range of 
               output X values; the default is [5, 100].

 OPTIONAL INPUT-OUTPUT KEYWORD PARAMETER:
       SEED:    Seed value for RANDOMU function.    As described in the 
               documentation for RANDOMU, the value of SEED is updated on 
               each call to RANDOMP, and taken from the system clock if not
               supplied.   This keyword can be used to have RANDOMP give 
               identical results on different runs.
 OUTPUTS:
       X:    Vector of random numbers, distributed as a power law between
               specified range
 PROCEDURE:  
       "Transformation Method" for random variables is described in Bevington 
       & Robinson, "Data Reduction & Error Analysis for Physical Sciences", 2nd
       Edition (McGraw-Hill, 1992). p. 83.
       Output of RANDOMU function is transformed to power-law
       random variable.

 EXAMPLE:
       Create a stellar initial mass function (IMF) with 10000 stars
       ranging from 0.5 to 100 solar masses and a Salpeter slope.  Enter:

       RANDOMP,MASS,-2.35,10000,RANGE_X=[0.5,100]

 NOTES:
       Versions 5.1.1 and V5.2 of IDL have a bug in RANDOMU such that the SEED
       value is initialized to the same value at the start of each session,
       rather than being initialized by the system clock.    RANDOMP will be
       affected in a similar manner.
 MODIFICATION HISTORY:
       Written by R. S. Hill, Hughes STX, July 13, 1995
       July 14, 1995   SEED keyword added at Landsman's suggestion.
                    Documentation converted to standard format.  RSH
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/math/randomp.pro)

RANDOMWISH

 NAME:
    RANDOMWISH
 PURUPOSE:
 ROUTINE TO DRAW RANDOM MATRICES FROM A WISHART DISTRIBUTION WITH DOF
 DEGREES OF FREEDOM AND SCALE MATRIX S.

 AUTHOR : BRANDON C. KELLY, STEWARD OBS., JULY 2006

 INPUTS :

   SEED - THE SEED FOR THE RANDOM NUMBER GENERATOR, CAN BE UNDEFINED.
   DOF - THE DEGREES OF FREEDOM FOR THE WISHART DISTRIBUTION.
   S - THE SCALE MATRIX. THE DIMENSION OF S CANNOT BE GREATER THAN
       DOF.

 OPTIONAL INPUTS :

   NRAND - THE NUMBER OF RANDOM MATRICES TO DRAW

 CALLED ROUTINES :

   MRANDOMN

(See $IDLUTILS_DIR/goddard/pro/math/randomwish.pro)

RDFITS_STRUCT

 NAME:
      RDFITS_STRUCT
 PURPOSE:
      Read an entire FITS file (all extensions) into a single IDL structure. 
 EXPLANATION:
      Each header, image or table array is placed in a separate structure 
      tag.

 CALLING SEQUENCE:
      RDFITS_STRUCT, filename, struct, /SILENT, /HEADER_ONLY, EXTEN= ]

 INPUT:
      FILENAME = Scalar string giving the name of the FITS file.  
                 One can also specify a gzip (.gz) compressed file 

 OPTIONAL KEYWORD: 
      /HEADER_ONLY - If set, then only the FITS headers (and not the data)
                are read into the structure.
      /SILENT - Set this keyword to suppress informational displays at the
               terminal.
 OUTPUT:
      struct = structure into which FITS data is read.   The primary header
             and image are placed into tag names HDR0 and IM0.   The ith
             extension is placed into the tag names HDRi, and either TABi
             (if it is a binary or ASCII table) or IMi (if it is an image
             extension)

             If /HEADER_ONLY is set, then struct will contain tags HDR0, HDR1
             ....HDRn containing all the headers of a FITS file with n 
             extensions
 OPTIONAL INPUT KEYWORD:
       EXTEN - positive integer array specifying which extensions to read.
             Default is to read all extensions. 
 PROCEDURES USED:
       FITS_OPEN, FITS_READ, FITS_CLOSE

 METHOD:
       The file is opened with FITS_OPEN which return information on the 
       number and type of each extension.    The CREATE_STRUCT() function
       is used iteratively, with FITS_READ calls to build the final structure.

 EXAMPLE:
       Read the FITS file 'm33.fits' into an IDL structure, st

       IDL> rdfits_struct, 'm33.fits', st
       IDL> help, /str, st                   ;Display info about the structure

       To just read the second and fourth extensions 
       IDL> rdfits_struct, 'm33.fits', st, exten=[2,4]
 RESTRICTIONS:
       Does not handle random groups or variable length binary tables
 MODIFICATION HISTORY:
       Written K. Venkatakrishna, STX April 1992
       Code cleaned up a bit  W. Landsman  STX  October 92
       Modified for MacOS     I.  Freedman  HSTX April 1994
       Work under Windows 95  W. Landsman   HSTX  January 1996
       Use anonymous structures, skip extensions without data WBL April 1998
       Converted to IDL V5.0, W. Landsman, April 1998
       OS-independent deletion of temporary file  W. Landsman  Jan 1999
       Major rewrite to use FITS_OPEN and CREATE_STRUCT() W. Landsman Sep 2002
       Added /HEADER_ONLY keyword   W. Landsman  October 2003
       Do not copy primary header into extension headers W. Landsman Dec 2004
       Do not modify NAXIS when using /HEADER_ONLY W. Landsman Jan 2005
       Added EXTEN keyword  W. Landsman July 2009

(See $IDLUTILS_DIR/goddard/pro/fits/rdfits_struct.pro)

RDFLOAT

 NAME:
      RDFLOAT
 PURPOSE:
      Quickly read a numeric ASCII data file into IDL floating/double vectors.
 EXPLANATION:
      Columns of data may be separated by tabs or spaces.      This 
      program is fast but is restricted to data files where all columns can 
      be read as floating point (or all double precision).   

      Use READCOL if  greater flexibility is desired.   Use READFMT to read a 
      fixed-format ASCII file.   Use FORPRINT to print columns of data.

 CALLING SEQUENCE:
      RDFLOAT, name, v1, [ v2, v3, v4, v5, ...  v19] 
                         COLUMNS, /DOUBLE, SKIPLINE = , NUMLINE = ]

 INPUTS:
      NAME - Name of ASCII data file, scalar string.  In VMS, an extension of 
              .DAT is assumed, if not supplied.

 OPTIONAL INPUT KEYWORDS:
      COLUMNS - Numeric scalar or vector specifying which columns in the file
               to read.    For example, if COLUMNS = [3,7,11] then the first
               output variable (v1) would contain column 3, the second would
               contain column 7 and the third would contain column 11.   If
               the number of elements in the COLUMNS vector is less than the
               number of output parameters, then consecutive columns are 
               implied.    For example, if 3 output parameters are supplied
               (v1,v2,v3) and COLUMNS = 3, then columns 3,4, and 5 will be
               read.   
      SKIPLINE - Integer scalar specifying number of lines to skip at the top
              of file before reading.   Default is to start at the first line.
      NUMLINE - Integer scalar specifying number of lines in the file to read.  
             Default is to read the entire file
      /DOUBLE - If this keyword is set, then all variables are read in as
              double precision.
      /SILENT - Set this keyword to suppress any informative messages

 OUTPUTS:
      V1,V2,V3,...V19 - IDL vectors to contain columns of data.
               Up to 19 columns may be read.  All output vectors are of type
               float, unless the /DOUBLE keyword is set, 

 EXAMPLES:
      Each row in a file 'position.dat' contains a star number and 6 columns
      of data giving an RA and Dec in sexigesimal format.   Read into IDL 
      variables.     

       IDL> rdfloat,'position.dat',ID,hr,min,sec,deg,dmin,dsec  

       All output vectors will be floating point.    To only read the 
       declination vectors (Deg,dmin,dsec)

       IDL> rdfloat,'position.dat',deg,dmin,dsec,col=4

 RESTRICTIONS:
      (1) All rows in the file must be formatted identically (except for 
          those skipped by SKIPLINE).    RDFLOAT reads the first line of 
          the data (after SKIPLINE) to determine the number of columns of 
          data.
      (2) Cannot be used to read strings
 PROCEDURES USED:
      None.
 REVISION HISTORY:
      Written         W. Landsman                 September 1995
      Call NUMLINES() function                    February 1996
      Read up to 19 columns                       August 1997
      Converted to IDL V5.0   W. Landsman         September 1997
      Allow to skip more than 32767 lines  W. Landsman  June 2001
      Added /SILENT keyword   W. Landsman         March 2002
      Added COLUMNS keyword, use STRSPLIT    W. Landsman May 2002
      Use SKIP_LUN if V5.6 or later          W. Landsman Nov 2002
      V5.6 version, use FILE_LINES()         W. Landsman Dec 2002

(See $IDLUTILS_DIR/goddard/pro/misc/rdfloat.pro)

RDPLOT

 NAME:
   RDPLOT

 PURPOSE:
   Like CURSOR but with a full-screen cursor and continuous readout option

 EXPLANATION:
   This program is designed to essentially mimic the IDL CURSOR command,
   but with the additional options of continuously printing out the data
   values of the cursor's position, and using a full-screen cursor rather 
   than a small cross cursor.  The full screen cursor uses OPLOT and 
   X-windows graphics masking to emulate the cursor.
      One difference is that IF the PRINT keyword is set but the DOWN,
   WAIT, CHANGE, or NOWAIT keywords are not set, then the leftmost mouse
   button will print a "newline" line-feed, but not exit.

 CALLING SEQUENCE:
   RDPLOT [, X, Y] [, WaitFlag] [, /DATA | /DEVICE | /NORMAL]
      [, /NOWAIT | /WAIT | /DOWN | /CHANGE] 
      [, /FULLCURSOR] [, /NOCLIP] [, /CROSS] [, /ACCUMULATE]
      [, ERR=, PRINT=, XTITLE=, YTITLE=, XVALUES=, YVALUES=
       , LINESTYLE=, THICK=, COLOR=, BACKGROUND=]

 REQUIRED INPUTS:
   None.

 OPTIONAL INPUTS: 
   WAITFLAG = Uses the same table as the intrinsic CURSOR command, But note
	that unlike the CURSOR command, there is no UP keyword.
		WaitFlag=0 sets the NOWAIT keyword
		WaitFlag=1 sets the WAIT keyword {default}
		WaitFlag=2 sets the CHANGE keyword
		WaitFlag=3 sets the DOWN keyword

 OPTIONAL OUTPUTS:
    X - a named variable to receive the final cursor X position, scalar
        or vector (if /ACCUMULATE is set)
    Y - a named variable to receive the final cursor Y position, scalar
        or vector (if /ACCUMULATE is set)
 OPTIONAL KEYWORD INPUT PARAMETERS:
   /DATA - data coordinates are displayed and returned.
   /DEVICE - device coordinates are displayed and returned.
   /NORMAL - normal coordinates are displayed and returned.
      Default is to use DATA coordinates if available (see notes).
   /NOWAIT = if non-zero the routine will immediately return the cursor's
      present position.
   /WAIT - if non-zero will wait for a mouse key click before returning.  If
      cursor key is already down, then procedure immediately exits.
   /DOWN - equivalent to WAIT *except* that if the mouse key is already down
      when the procedure is called, the procedure will wait until the mouse
      key is clicked down again.
   /CHANGE - returns when the mouse is moved OR a key is clicked up or down.
   PRINT = if non-zero will continuously print out (at the terminal) the data 
      values of the cursor's position.  If PRINT>1, program will printout a 
      brief header describing the mouse button functions.  However, note that 
      the button functions are overridden if any of the DOWN, WAIT, or
      CHANGE values are non-zero.
   XTITLE = label used to describe the values of the abscissa if PRINT>0.
   YTITLE = label used to describe the values of the ordinate if PRINT>0.
   XVALUES = a vector corresponding to the values to be printed when the
	PRINT keyword is set.  This allows the user the option of printing
	out other values rather than the default X coordinate position of
	the cursor.  E.g., if XVALUES is a string vector of dates such as
	['May 1', 'May 2', ...], then those dates will be printed rather than
	the X value of the cursor's position: if X=1 then 'May 2' would be
	printed, etc.  This requires that the values of the X coordinate read
	by the cursor must be positive (can't access negative elements).
       If XVALUES=-1, then NO values for X will be printed.
   YVALUES = analogous to the XVALUES keyword.
   /FULLCURSOR - if non-zero default cursor is blanked out and full-screen 
      (or full plot window, depending on the value of NOCLIP) lines are
      drawn; their intersecton is centered on the cursor position.
   /NOCLIP - if non-zero will make a full-screen cursor, otherwise it will
      default to the value in !P.NOCLIP.
   LINESTYLE = style of line that makes the full-screen cursor.
   THICK = thickness of the line that makes the full-screen cursor.
   COLOR = color of the full-screen cursor.
   BACKGROUND = color of the background of the plot device.  If this has
      been set to !P.BackGround, then this keyword is unnecessary.
   CROSS = if non-zero will show the regular cross AND full screen cursors.
   /ACCUMULATE - all of the positions for which the left button was
      clicked are stored in the X and Y variables.  Has no effect if X and Y 
      are not present.

 OPTIONAL KEYWORD OUTPUT PARAMETER:
   ERR = returns the most recent value of the !mouse.button value.

 NOTES:
   Note that this procedure does not allow the "UP" keyword/flag...which 
   doesn't seem to work too well in the origianl CURSOR version anyway.

   If a data coordinate system has not been established, then RDPLOT will
   create one identical to the device coordinate system.   Note that this
   kluge is required even if the user specified /NORMAL coordinates, since
   RDPLOT makes use of the OPLOT procedure.  This new data coordinate system
   is effectively "erased" (!X.CRange and !Y.CRange are both set to zero)
   upon exit of the routine so as to not change the plot status from the
   user's point of view.

   Only tested on X-windows systems.  If this program is interrupted, the
   graphics function might be left in a non-standard state; in that case,
   run the program RESET_RDPLOT to return the standard graphics functions,
   or type the command:   DEVICE, /CURSOR_CROSS, SET_GRAPHICS=3, BYPASS=0

   Robishaw added /ACCUMULATE keyword to pass back all the positions at
   which the mouse was left-clicked.  In addition, the value of the exit
   click is returned unless the cursor did not change position between the
   last left-click and the exit click.

 BUGS:
   NOTE: (1/27/05) The bugs below have been fixed by Robishaw and tested
   on Solaris, Linux and OS-X.

   It is assumed that the current background of the plot is correctly
   defined by the value in !P.Background.  Otherwise, the color of the
   long cursor probably will not be correct.  Sometimes the color doesn't
   work anyway, and I'm not sure why.
   NOTE: Robishaw fixed this 1/27/05.

   There may be some cases (e.g., when THICK>1 and NOCLIP=0) when the
   full-screen cursor is not correctly erased, leaving "ghost images" on the
   plot.  It just seems that the screen updates get slow or the positions
   ambiguous with a thick line and the cursor off the plot.
   NOTE: Robishaw fixed this 1/27/05.

 PROCEDURE:
   Basically is a bells-n-whistles version of the CURSOR procedure.  All
   the details are covered in the above discussion of the keywords.

 EXAMPLES:
   A silly, but informative one:
   Months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', $
             'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
   plot, indgen(12), xrange=[-5, 15]
   rdplot, /FULL, /PRINT, XTITLE='Month: ', YTITLE='Y-value per month = ', $
      xvalues=Months

   If your plot has a non-black background color, be sure to set either
   !p.background or the BACKGROUND keyword.  Here are examples of how to
   use a blue full-screen cursor on a plot with a red background and
   yellow axes and data. First, deal with color decomposition off:
   device, decomposed=0
   tvlct, [255,255,0], [0,255,0], [0,0,255], 1
   plot, randomn(seed,1024), XSTYLE=19, PSYM=3, COLOR=2, BACK=1
   rdplot, /PRINT, /FULL, THICK=5, /NOCLIP, BACK=1, COLOR=3

   For decomposition on (TrueColor or DirectColor only):
   device, decomposed=1
   plot, randomn(seed,1024), XSTYLE=19, PSYM=3, COLOR=65535l, BACK=255l
   rdplot, /PRINT, /FULL, THICK=5, /NOCLIP, BACK=255l, COLOR=16711680l

 MODIFICATION HISTORY:
   Written (originally named CURFULL) by J.Wm.Parker  1993 Nov 22 
   Created data coordinates if not already present, W. Landsman Nov. 93
   Added continuous printout of data values, COLOR and FULLCURSOR keywords
      (so that default is that it acts just like the cursor command).
      Changed name from CURFULL to RDPLOT.   J.Wm.Parker  1994 Apr 20
   Modified (with some translation table assistance from the IDL support 
      group) to correctly plot the crosshair with the desired IDL 
      color using the device's translation table to determine the XOR 
      function and using the BYPASS function.  Added the RESET_RDPLOT
      procedure to cleanup crashes that might occur while running
      RDPLOT.  Other minor changes/bug fixes.  J.Wm.Parker  1994 May 21
   Modified DOWN, WAIT, CHANGE functions to behave more similar to the
      generic CURSOR procedure.   J.Wm.Parker  1995 April 24
   Added XVALUES, YVALUES keywords and cleanup.   J.Wm.Parker  1995 April 24
   Convert to IDL V5.0,  W. Landsman    July 1998
   Change !D.NCOLORS to !D.TABLE_SIZE for 24 bit displays W. Landsman May 2000
   Skip translation table for TrueColor visuals   W. Landsman  March 2001
   Fixed /FULLCURSOR ghosts. Fixed to properly deal with background colors
      in 24-bit visual classes (TrueColor and DirectColor).  Added
      BACKGROUND keyword. Tim Robishaw 2005 Jan 27       
   Added /ACCUMULATE keyword. T. Robishaw 2006 Nov 8
   Corrected following problems. When /CHANGE and /PRINT were set,
      returned X & Y were different than those printed.  When /PRINT and
      /NOWAIT were set, or /PRINT and /WAIT were set and the routine was
      entered with a mouse button clicked, nothing was printed. When
      /PRINT and /DOWN were set, if routine was started with button down,
      advertised behavior was that routine would exit on next down click;
      in practice if cursor was not moved, successive down clicks had no
      effect.  Now, if X is passed as an output variable, requires that Y
      is also passed, like CURSOR.  Bottom line is that RDPLOT now really
      does behave like CURSOR and when /PRINT is set, the values printed
      correspond to those returned in X & Y.  T. Robishaw 2006 Nov 12
   Fixed misbehavior when color decomposition was set to off for
      TrueColor and DirectColor.  Now thoroughly tested on PseudoColor
      displays as well as both decomposition states for TrueColor and
      DirectColor.  Also made the default cursor color white when
      decomposition is on (this has been its default value for
      decomposition off). T. Robishaw 2006 Nov 16

(See $IDLUTILS_DIR/goddard/pro/plot/rdplot.pro)

RDPSF

 NAME:
       RDPSF
 PURPOSE:
       Read the FITS file created by GETPSF in the DAOPHOT sequence 
 EXPLANATION:
       Combines the Gaussian with the residuals to create an output PSF array.

 CALLING SEQUENCE:
       RDPSF, PSF, HPSF, [ PSFname]

 OPTIONAL INPUTS
       PSFname - string giving the name of the FITS file containing the PSF
               residuals

 OUTPUTS
       psf - array containing the actual PSF
       hpsf - header associated with psf

 PROCEDURES CALLED:
       DAO_VALUE(), MAKE_2D, SXADDPAR, READFITS(), SXPAR()
 REVISION HISTORY:
       Written W. Landsman              December, 1988
       Checked for IDL Version 2, J. Isensee & J. Hill, December, 1990
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/idlphot/rdpsf.pro)

READCOL

 NAME:
       READCOL
 PURPOSE:
       Read a free-format ASCII file with columns of data into IDL vectors 
 EXPLANATION:
       Lines of data not meeting the specified format (e.g. comments) are 
       ignored.  By default, columns may be separated by commas or spaces.

       Use READFMT to read a fixed-format ASCII file.   Use RDFLOAT for
       much faster I/O (but less flexibility).    Use FORPRINT to write 
       columns of data (inverse of READCOL).   

       If you sure that all lines meet the specified format (excluding 
       commented and SKIPed lines) then the speed for reading large files
       can be significantly improved by setting the /QUICK keyword.

 CALLING SEQUENCE:
       READCOL, name, v1, [ v2, v3, v4, v5, ...  v40 , COMMENT=, /NAN
           DELIMITER= ,FORMAT = , /DEBUG ,  /SILENT , SKIPLINE = , NUMLINE = 
           COUNT =, STRINGSKIP= 

 INPUTS:
       NAME - Name of ASCII data file, scalar string.  

 OPTIONAL INPUT KEYWORDS:
       FORMAT - scalar string containing a letter specifying an IDL type
               for each column of data to be read.  Allowed letters are 
               A - string data, B - byte, D - double precision, F- floating 
               point, I - short integer, L - longword, LL - 64 bit integer, 
               U - unsigned short integer, UL - unsigned long integer 
               Z - longword hexadecimal, and X - skip a column.

               Columns without a specified format are assumed to be floating 
               point.  Examples of valid values of FMT are

       'A,B,I'        ;First column to read as a character string, then 
                       1 column of byte data, 1 column integer data
       'L,L,L,L'       ;Four columns will be read as longword arrays.
       ' '             ;All columns are floating point

       If a FORMAT keyword string is not supplied, then all columns are 
       assumed to be floating point.

       /SILENT - Normally, READCOL will display each line that it skips over.
               If SILENT is set and non-zero then these messages will be 
               suppressed.
       /DEBUG - If this keyword is non-zero, then additional information is
                printed as READCOL attempts to read and interpret the file.
       COMMENT - single character specifying comment character.   Any line 
                beginning with this character will be skipped.   Default is
                no comment lines.
       /COMPRESS - If set, then the file is assumed to be gzip compressed.
                There is no automatic recognition of compressed files
                by extension type.
       DELIMITER - Character(s) specifying delimiter used to separate 
                columns.   Usually a single character but, e.g. delimiter=':,'
                specifies that either a colon or comma as a delimiter. 
                Set DELIM = string(9b) to read tab separated data
                The default delimiter is either a comma or a blank.
       /NAN - if set, then an empty field will be read into a floating or 
                double numeric variable as NaN; by default an empty field is 
                converted to 0.0.
       /PRESERVE_NULL - If set, then spaces are considered to be valid fields,
                useful if the columns contain missing data.   Note that between
                April and December 2006, /PRESERVE_NULL was the default.
       /QUICK -  If set, then READCOL does not check that each individual line
                matches the supplied format.     This makes READCOL less 
                flexible but can provide a significant speed improvement when
                reading large files.                       
       SKIPLINE - Scalar specifying number of lines to skip at the top of file
               before reading.   Default is to start at the first line.
       NUMLINE - Scalar specifying number of lines in the file to read.  
               Default is to read the entire file
       STRINGSKIP - will skip all lines that begin with the specified string.
               (Unlike COMMENT this can be more than 1 character.) Useful to 
               skip over comment lines.

 OUTPUTS:
       V1,V2,V3,...V40 - IDL vectors to contain columns of data.
               Up to 40 columns may be read.  The type of the output vectors
               are as specified by FORMAT.

 OPTIONAL OUTPUT KEYWORDS:
       COUNT - integer giving the number of valid lines actually read
       NLINES - integer giving the total number of lines in the file 
                (as returned by FILE_LINES)

 EXAMPLES:
       Each row in a file position.dat contains a star name and 6 columns
       of data giving an RA and Dec in sexigesimal format.   Read into IDL 
       variables.   (NOTE: The star names must not include the delimiter 
       as a part of the name, no spaces or commas as default.)

       IDL> FMT = 'A,I,I,F,I,I,F'
       IDL> READCOL,'position.dat',F=FMT,name,hr,min,sec,deg,dmin,dsec  

       The HR,MIN,DEG, and DMIN variables will be integer vectors.

       Alternatively, all except the first column could be specified as
       floating point.

       IDL> READCOL,'position.dat',F='A',name,hr,min,sec,deg,dmin,dsec 

       To read just the variables HR,MIN,SEC
       IDL> READCOL,'position.dat',F='X,I,I,F',HR,MIN,SEC

 RESTRICTIONS:
       This procedure is designed for generality and not for speed.
       If a large ASCII file is to be read repeatedly, it may be worth
       writing a specialized reader.

       Columns to be read as strings must not contain the delimiter character
       (i.e. commas or spaces by default).   Either change the default 
       delimiter with the DELIMITER keyword, or use READFMT to read such files.

       Numeric values are converted to specified format.  For example,
       the value 0.13 read with an 'I' format will be converted to 0.

 PROCEDURES CALLED
       GETTOK(), STRNUMBER()
       The version of STRNUMBER() must be after August 2006.
 REVISION HISTORY:
       Written         W. Landsman                 November, 1988
       Modified             J. Bloch                   June, 1991
       (Fixed problem with over allocation of logical units.)
       Added SKIPLINE and NUMLINE keywords  W. Landsman    March 92
       Read a maximum of 25 cols.  Joan Isensee, Hughes STX Corp., 15-SEP-93.
       Call NUMLINES() function W. Landsman          Feb. 1996
       Added DELIMITER keyword  W. Landsman          Nov. 1999
       Fix indexing typos (i for k) that mysteriously appeared W. L. Mar. 2000
       Hexadecimal support added.  MRG, RITSS, 15 March 2000.
       Default is comma or space delimiters as advertised   W.L. July 2001
       Faster algorithm, use STRSPLIT if V5.3 or later  W.L.  May 2002
       Accept null strings separated by delimiter ,e.g. ',,,'
       Use SCOPE_VARFETCH instead of EXECUTE() for >V6.1  W.L. Jun 2005
       Added compile_opt idl2   W. L.  July 2005
       Added the NaN keyword   W. L      August 2006
       Added /PRESERVE_NULL keyword  W.L.  January 2007
       Assume since V5.6 (FILE_LINES available ) W.L. Nov 2007
       Added COUNT output keyword  W.L.  Aug 2008
       Added NLINES output keyword W.L.   Nov 2008
       Added SKIPSTART keyword  Stephane Beland January 2008
       Renamed SKIPSTART to STRINGSKIP to keep meaning of SKIP W.L. Feb 2008
       Assume since V6.1, SCOPE_VARFETCH available W.L. July 2009
       Read up to 40 columns W.L. Aug 2009
       Use pointers instead of SCOPE_VARFETCH. Fixes bug with
       IDL Workbench and runs 20% faster Douglas J. Marshall/W.L. Nov 2009
       Recognize  LL, UL, and ULL data types, don't use 'val' output from 
           STRNUMBER()   W.L.  Feb 2010
       Graceful return even if no valid lines are present D. Sahnow April 2010
       Ability to read tab separated data WL April 2010
       Free memory used by pointers  WL  July 2010
       Added /QUICK keyword  WL  Sep 2010
       Accept normal FORTRAN formats (e.g. F5.1) P. Noterdaeme/W.L Jan 2011
       Add COMPRESS keyword, IDL 6 notation W. Landsman/J. Bailin   Feb 2011
       Allow filename to be 1 element array W.Landsman/S.Antonille Apr 2011

(See $IDLUTILS_DIR/goddard/pro/misc/readcol.pro)

READFITS

 NAME:
       READFITS
 PURPOSE:
       Read a FITS file into IDL data and header variables. 
 EXPLANATION:
       READFITS() can read FITS files compressed with gzip or Unix (.Z) 
       compression.  FPACK ( http://heasarc.gsfc.nasa.gov/fitsio/fpack/ )
       compressed FITS files can also be read provided that the FPACK software
       is installed.
       See http://idlastro.gsfc.nasa.gov/fitsio.html for other ways of
       reading FITS files with IDL.   

 CALLING SEQUENCE:
       Result = READFITS( Filename/Fileunit,[ Header, heap, /NOSCALE, EXTEN_NO=,
                     NSLICE=, /SILENT , STARTROW =, NUMROW = , HBUFFER=,
                     /CHECKSUM, /COMPRESS, /FPACK, /No_Unsigned, NaNVALUE = ]

 INPUTS:
       Filename = Scalar string containing the name of the FITS file  
                 (including extension) to be read.   If the filename has
                  a *.gz extension, it will be treated as a gzip compressed
                  file.   If it has a .Z extension, it will be treated as a
                  Unix compressed file.     If Filename is an empty string then
                  the user will be queried for the file name.
                                   OR
       Fileunit - A scalar integer specifying the unit of an already opened
                  FITS file.  The unit will remain open after exiting 
                  READFITS().  There are two possible reasons for choosing 
                  to specify a unit number rather than a file name:
          (1) For a FITS file with many extensions, one can move to the 
              desired extensions with FXPOSIT() and then use READFITS().  This
              is more efficient than repeatedly starting at the beginning of 
              the file.
          (2) For reading a FITS file across a Web http: address after opening
              the unit with the SOCKET procedure 

 OUTPUTS:
       Result = FITS data array constructed from designated record.
                If the specified file was not found, then Result = -1

 OPTIONAL OUTPUT:
       Header = String array containing the header from the FITS file.
              If you don't need the header, then the speed may be improved by
              not supplying this parameter.    Note however, that omitting 
              the header can imply /NOSCALE, i.e. BSCALE and BZERO values
              may not be applied.
       heap = For extensions, the optional heap area following the main
              data array (e.g. for variable length binary extensions).

 OPTIONAL INPUT KEYWORDS:
       /CHECKSUM - If set, then READFITS() will call FITS_TEST_CHECKSUM to 
                verify the data integrity if CHECKSUM keywords are present
                in the FITS header.   Cannot be used with the NSLICE, NUMROW
                or STARTROW keywords, since verifying the checksum requires 
               that all the data be read.  See FITS_TEST_CHECKSUM() for more
               information.

       /COMPRESS - Signal that the file is gzip compressed.  By default, 
               READFITS will assume that if the file name extension ends in 
               '.gz' then the file is gzip compressed.   The /COMPRESS keyword
               is required only if the the gzip compressed file name does not 
               end in '.gz' or .ftz
              

       EXTEN_NO - non-negative scalar integer specifying the FITS extension to
               read.  For example, specify EXTEN = 1 or /EXTEN to read the 
               first FITS extension.   

       /FPACK - Signal that the file is compressed with the FPACK software. 
               http://heasarc.gsfc.nasa.gov/fitsio/fpack/ ) By default, 
               (READFITS will assume that if the file name extension ends in 
               .fz that it is fpack compressed.     The FPACK software must
               be installed on the system 
   
        HBUFFER - Number of lines in the header, set this to slightly larger
                than the expected number of lines in the FITS header, to 
               improve performance when reading very large FITS headers. 
               Should be a multiple of 36 -- otherwise it will be modified
               to the next higher multiple of 36.   Default is 180

       /NOSCALE - If present and non-zero, then the ouput data will not be
                scaled using the optional BSCALE and BZERO keywords in the 
                FITS header.   Default is to scale.

       /NO_UNSIGNED - By default, if the header indicates an unsigned integer 
               (BITPIX = 16, BZERO=2^15, BSCALE=1) then READFITS() will output 
               an IDL unsigned integer data type (UINT).   But if /NO_UNSIGNED
               is set, then the data is converted to type LONG.  

       NSLICE - An integer scalar specifying which N-1 dimensional slice of a 
                N-dimensional array to read.   For example, if the primary 
                image of a file 'wfpc.fits' contains a 800 x 800 x 4 array, 
                then 

                 IDL> im = readfits('wfpc.fits',h, nslice=2)
                           is equivalent to 
                 IDL> im = readfits('wfpc.fits',h)
                 IDL> im = im[*,*,2]
                 but the use of the NSLICE keyword is much more efficient.
                 Note that any degenerate dimensions are ignored, so that the
                 above code would also work with a 800 x 800 x 4 x 1 array.

       NUMROW -  Scalar non-negative integer specifying the number of rows 
                 of the image or table extension to read.   Useful when one 
                 does not want to read the entire image or table.  

       POINT_LUN  -  Position (in bytes) in the FITS file at which to start
                 reading.   Useful if READFITS is called by another procedure
                 which needs to directly read a FITS extension.    Should 
                 always be a multiple of 2880, and not be used with EXTEN_NO
                 keyword.

       /SILENT - Normally, READFITS will display the size the array at the
                 terminal.  The SILENT keyword will suppress this

        STARTROW - Non-negative integer scalar specifying the row
               of the image or extension table at which to begin reading. 
               Useful when one does not want to read the entire table.  

       NaNVALUE - This keyword is included only for backwards compatibility
                  with routines that require IEEE "not a number" values to be
                  converted to a regular value.

       /UNIXPIPE - When a FileUnit is supplied to READFITS(), then /UNIXPIPE
                 indicates that the unit is to a Unix pipe, and that 
                 no automatic byte swapping is performed.

 EXAMPLE:
       Read a FITS file test.fits into an IDL image array, IM and FITS 
       header array, H.   Do not scale the data with BSCALE and BZERO.

              IDL> im = READFITS( 'test.fits', h, /NOSCALE)

       If the file contains a FITS extension, it could be read with

              IDL> tab = READFITS( 'test.fits', htab, /EXTEN )

       The function TBGET() can be used for further processing of a binary 
       table, and FTGET() for an ASCII table.
       To read only rows 100-149 of the FITS extension,

              IDL> tab = READFITS( 'test.fits', htab, /EXTEN, 
                                   STARTR=100, NUMR = 50 )

       To read in a file that has been compressed:

              IDL> tab = READFITS('test.fits.gz',h)

 ERROR HANDLING:
       If an error is encountered reading the FITS file, then 
               (1) the system variable !ERROR_STATE.CODE is set negative 
                   (via the MESSAGE facility)
               (2) the error message is displayed (unless /SILENT is set),
                   and the message is also stored in !!ERROR_STATE.MSG
               (3) READFITS returns with a value of -1
 RESTRICTIONS:
       (1) Cannot handle random group FITS

 NOTES:
       (1) If data is stored as integer (BITPIX = 16 or 32), and BSCALE
       and/or BZERO keywords are present, then the output array is scaled to 
       floating point (unless /NOSCALE is present) using the values of BSCALE
       and BZERO.   In the header, the values of BSCALE and BZERO are then 
       reset to 1. and 0., while the original values are written into the 
       new keywords O_BSCALE and O_BZERO.     If the BLANK keyword was
       present (giving the value of undefined elements *prior* to the 
       application of BZERO and BSCALE) then the *keyword* value will be
       updated with the values of BZERO and BSCALE.
       
       (2) The use of the NSLICE keyword is incompatible with the NUMROW
       or STARTROW keywords.

       (3) On some Unix shells, one may get a "Broken pipe" message if reading
        a Unix compressed (.Z) file, and not reading to the end of the file 
       (i.e. the decompression has not gone to completion).     This is an 
        informative message only, and should not affect the output of READFITS.   
 PROCEDURES USED:
       Functions:   SXPAR()
       Procedures:  MRD_SKIP, SXADDPAR, SXDELPAR

 MODIFICATION HISTORY:
       Original Version written in 1988, W.B. Landsman   Raytheon STX
       Revision History prior to October 1998 removed          
       Major rewrite to eliminate recursive calls when reading extensions
                  W.B. Landsman  Raytheon STX                    October 1998
       Add /binary modifier needed for Windows  W. Landsman    April 1999
       Read unsigned datatypes, added /no_unsigned   W. Landsman December 1999
       Output BZERO = 0 for unsigned data types   W. Landsman   January 2000
       Update to V5.3 (see notes)  W. Landsman                  February 2000
       Fixed logic error in use of NSLICE keyword  W. Landsman  March 2000
       Fixed byte swapping for Unix compress files on little endian machines
                                    W. Landsman    April 2000
       Added COMPRESS keyword, catch IO errors W. Landsman September 2000
       Option to read a unit number rather than file name W.L    October 2001
       Fix undefined variable problem if unit number supplied W.L. August 2002
       Don't read entire header unless needed   W. Landsman  Jan. 2003
       Added HBUFFER keyword    W. Landsman   Feb. 2003
       Added CHECKSUM keyword   W. Landsman   May 2003
       Restored NaNVALUE keyword for backwards compatibility,
               William Thompson, 16-Aug-2004, GSFC
       Recognize .ftz extension as compressed  W. Landsman   September 2004
       Fix unsigned integer problem introduced Sep 2004 W. Landsman Feb 2005
       Don't modify header for unsigned integers, preserve double precision
           BSCALE value  W. Landsman March 2006
       Use gzip instead of compress for Unix compress files W.Landsman Sep 2006
       Call MRD_SKIP to skip bytes on different file types W. Landsman Oct 2006
       Make ndata 64bit for very large files E. Hivon/W. Landsman May 2007
       Fixed bug introduced March 2006 in applying Bzero C. Magri/W.L. Aug 2007
       Check possible 32bit overflow when using NSKIP W. Landsman Mar 2008
       Always reset BSCALE, BZERO even for unsigned integers W. Landsman May 2008
       Make ndata 64bit for very large extensions J. Schou/W. Landsman Jan 2009
       Use PRODUCT() to compute # of data points  W. Landsman  May 2009
       Read FPACK compressed file via UNIX pipe. W. Landsman May 2009
       Fix error using NUMROW,STARTROW with non-byte data, allow these 
           keywords to be used with primary array  W. Landsman July 2009
       Ignore degenerate trailing dimensions with NSLICE keyword W.L. Oct 2009
       Add DIALOG_PICKFILE() if filename is an empty string  W.L. Apr 2010
       Set BLANK values *before* applying BSCALE,BZERO, use short-circuit
           operators  W.L. May 2010
      Skip extra SPAWN with FPACK decompress J. Eastman, W.L. July 2010
      Fix possible problem when startrow=0 supplied J. Eastman/W.L. Aug 2010
      First header is not necessarily primary if unit supplied WL Jan 2011

(See $IDLUTILS_DIR/goddard/pro/fits/readfits.pro)

READFMT

 NAME:
     READFMT
 PURPOSE:
       Quickly read a fixed format ASCII data file into IDL variables. 
 EXPLANATION:
       Lines of data not meeting the specified format (e.g. comments) are
       ignored.  
      
       To read a free format ASCII data file use the procedures 
       READCOL or RDFLOAT.     To print (formatted or free) columns of data
       use the procedure FORPRINT.   

 CALLING SEQUENCE:
       READFMT, name, fmt, v1,[ v2, v3, v4, ..., v25 , 
                          /SILENT, /DEBUG, SKIPLINE= , NUMLINE =]

 INPUTS:
       NAME - Name of ASCII data file.  An extension of .DAT is assumed,
               if not supplied.
       FMT - scalar string containing a valid FORTRAN read format.
               Must include a field length specification.   Cannot include
               internal parenthesis.  A format field must be included for 
               each output vector.   Multiple format fields are allowed, but
               the repetition factor must be less than 100, (.i.e. 19X is 
               allowed but 117X is illegal) 

       Examples of valid FMT values are
               FMT = 'A7,3X,2I4'  or FMT = '1H ,5I7,2A7'
       Examples of INVALID FMT values are
               FMT = 'A7,B3'           ;'B' is not a valid FORTRAN format
               FMT = 'A7,2(I3,F5.1)'   ;Internal parenthesis not allowed
               FMT = 'A7,F,I'          ;Field length not included

 OUTPUTS:
       V1,V2,V3,V4... - IDL vectors to contain columns of data.
               Up to 25 output vectors may be read.  The type of the output 
               vectors are specified by FMT.

 OPTIONAL KEYWORD INPUTS:
       /SILENT - If this keyword is set and non-zero, then certain terminal
               output is suppressed while reading the file
       /DEBUG - Set this keyword to display additional information while
               reading the file.
       SKIPLINE - Scalar specifying number of lines to skip at the top of
               file before reading. Default is to start at first line
       NUMLINE - Scalar specifying number of lines in the file to read.
               Default is to read the entire file 

 EXAMPLES:
       Each row in a fixed-format file POSITION.DAT contains a 5 character 
       star name  and 6 columns of data giving an RA and Dec in sexigesimal 
       format.   A possible format for such data might be

       IDL> FMT = 'A5,2I3,F5.1,2x,3I3'    
       and the file could be quickly read with

       IDL> READFMT,'POSITION', fmt, name, hr, min, sec, deg, dmin, dsec 
    
       NAME will be a string vector,SEC will be a floating point vector, and
       the other vectors will be of integer type.

 RESTRICTIONS:
       This procedure is designed for generality and not for speed.
       If a large ASCII file is to be read repeatedly, it may be worth
       writing a specialized reader.

 NOTES:
       When reading a field with an integer format I<n>, the output vector is
               byte  - if n = 1
               integer*2 - if 1 < n < 5
               integer*4  - in all other cases
       Octal ('O') and hexadecimal ('Z') formats are read into longwords

 PROCEDURE CALLS:
       GETTOK(), REMCHAR, ZPARCHECK

 REVISION HISTORY:
       Written         W. Landsman                 November, 1988
       Added SKIPLINE and NUMLINE keywords         March 92
       Allow up to 25 columns to be read           June 92
       Call NUMLINES() function                    Feb 1996
       Recognize 'O' and 'Z' formats  W. Landsman   September 1997
       Recognize 'G' format, use SKIP_LUN   W. Landsman  May 2010

(See $IDLUTILS_DIR/goddard/pro/misc/readfmt.pro)

READ_FMR

 NAME:
  READ_FMR

 PURPOSE:
   Read a journal (ApJ, AJ) machine-readable table into IDL

 EXPLANATION:
  Given a machine readable table name and optionally column
  numbers, this FUNCTION reads the format information in the
  meta-header and outputs a IDL function containing either the
  complete table or only the requested columns.

 CALLING SEQUENCE:
  data = read_fmr(filename)

 INPUTS:
  filename [STRING]: the name of the file containing the machine
  readable table. If filename is missing a dialog to select the
  filename will be presented

 INPUT KEYWORD PARAMETERS:
   /HELP  - if set show the help

   COLUMNS -  [(array of) integers or strings] of column(s) to be returned.
     If columns is of type integer they represent indices for which
     column numbers to return, if they are strings the columns with the
     corresponding names will be returned in the order as given.

   MISSINGVALUE [float]: value with which to replace the missing values in the 
        table, default is NaN.

   /USE_COLNUM - If  specified and non-zero then column names will be generated
        as 'C1, C2,  .... Cn'  for the number of columns in the table, rather
        than using the table names.

 OUTPUTS:
  The ouput data structure will look like:
    TYPE            STRING    'mr_structure'
    NAME            STRING    Array[X]
    UNIT            STRING    Array[X]
    DESCRIPTION     STRING    Array[X]
    DATA            STRUCT    -> <Anonymous> Array[1]
  where name contains the names of each columns
  unit contains the given units
  description contains the short descriptions and
  data holds the values of the separate columns.   By default the tag names are
  taken from the column names, with modifications necessary to make them a 
  valid tag name.    For example, the column name 'B-V' will be converted to 
  'B_V' to become a valid tag name.    If the /USE_COLNUM keyword is set, then
  the column will be named  C0,  C1, ... , CX, where X stands for the total 
  number of columns read.

 RESTRICTIONS:
  (1) The file to be read should be formatted as a machine readable datafile.
  (2) Use of the COLUMN keyword currently requires use of the EXECUTE, and so
      cannot be used with the IDL Virtural machine.
 EXAMPLE:
  meas = read_fmr('smith.dat',col=[2,5,6], /Use_colnum)
   plot,meas.data.c1,ytitle=meas.name[1]+' ('+meas.unit[1]+')'

  and
  data = read_fmr('smith.dat',col=['Name','Date'], /Use_colnum)
   print,meas.data.c0
   
 MODIFICATION HISTORY:
  Version 1:
  Written by Sacha Hony (ESA) Nov 14 2003
   Based heavily on mrcolextract by Greg Schwarz (AAS Journals
   staff scientist) on 8/16/00.

  Version 1.1:
    Fixed bug where column=[3,4] always returned the first few columns

  VErsion 2.0 By default use column names as tag names W. Landsman Feb 2010

(See $IDLUTILS_DIR/goddard/pro/disk_io/read_fmr.pro)

READ_KEY

 NAME:
	READ_KEY
 PURPOSE:
	To read a keystroke and return its ASCII equivalent
 EXPLANATION:
	If an ESCAPE sequence was produced and  the sequence is
	recognized (e.g. up arrow), then a code is returned.

       This functionality is mostly made obsolete by the addition of the
       ESCAPE and KEY_NAME keywords to GET_KBRD in IDL V6.2

 CALLING SEQUENCE:
	key = READ_KEY(Wait)

 INPUTS:
	Wait  -  The wait flag.  If non-zero, execution is halted until a
	         key is struck.  If zero, execution returns immediately and
	         a zero is returned if there was no keystroke waiting in the
	         keyboard buffer.  If not specified, zero is assumed.

 OUTPUT:
	Returned - The key struck.  The ASCII code for non-escape sequences.
	           Escape sequence equivalents:
			Up Arrow     --  128
			Down Arrow   --  130
			Left Arrow   --  129
			Right Arrow  --  131
			Else         --    0

	The return value is a byte value.

 MODIFICATION HISTORY:
	Written by Michael R. Greason, STX, 22 June 1990.
	Rewritten for a SUN workstation.  MRG, STX, 23 August 1990.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/read_key.pro)

RECPOL

 NAME:
       RECPOL
 PURPOSE:
       Convert 2-d rectangular coordinates to polar coordinates.
 CATEGORY:
 CALLING SEQUENCE:
       recpol, x, y, r, a
 INPUTS:
       x, y = vector in rectangular form.           in
 KEYWORD PARAMETERS:
       Keywords:
         /DEGREES means angle is in degrees, else radians.
 OUTPUTS:
       r, a = vector in polar form: radius, angle.  out
 COMMON BLOCKS:
 NOTES:
 MODIFICATION HISTORY:
       R. Sterner. 18 Aug, 1986.
       Johns Hopkins University Applied Physics Laboratory.
       RES 13 Feb, 1991 --- added /degrees.
       R. Sterner, 30 Dec, 1991 --- simplified.
       R. Sterner, 25 May, 1993 --- Fixed atan (0,0) problem.

 Copyright (C) 1986, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/jhuapl/recpol.pro)

REMCHAR

 NAME:
	REMCHAR
 PURPOSE:
	Remove all appearances of character (char) from string (st)

 CALLING SEQUENCE:
	REMCHAR, ST, CHAR

 INPUT-OUTPUT:
	ST  - String from which character will be removed, scalar or vector  
 INPUT:
	CHAR- Single character to be removed from string or all elements of a
		string array 

 EXAMPLE:
	If a = 'a,b,c,d,e,f,g' then 

	IDL> remchar,a, ','

      will give a = 'abcdefg'

 REVISIONS HISTORY
	Written D. Lindler October 1986
	Test if empty string needs to be returned   W. Landsman  Feb 1991
	Work on string arrays    W. Landsman   August 1997
	Avoid 32 bit integer overflow K. Tolbert/W. Landsman Feb 2007

(See $IDLUTILS_DIR/goddard/pro/misc/remchar.pro)

REMOVE

 NAME:
       REMOVE
 PURPOSE:
       Contract a vector or up to 25 vectors by removing specified elements   
 CALLING SEQUENCE:
       REMOVE, index, v1,[ v2, v3, v4, v5, v6, ... v25]     
 INPUTS:
       INDEX - scalar or vector giving the index number of elements to
               be removed from vectors.  Duplicate entries in index are
               ignored.    An error will occur if one attempts to remove
               all the elements of a vector.     REMOVE will return quietly
               (no error message) if index is !NULL or undefined.

 INPUT-OUTPUT:
       v1 - Vector or array.  Elements specifed by INDEX will be 
               removed from v1.  Upon return v1 will contain
               N fewer elements, where N is the number of distinct values in
               INDEX.

 OPTIONAL INPUT-OUTPUTS:
       v2,v3,...v25 - additional vectors containing
               the same number of elements as v1.  These will be
               contracted in the same manner as v1.

 EXAMPLES:
       (1) If INDEX = [2,4,6,4] and V = [1,3,4,3,2,5,7,3] then after the call

               IDL> remove,index,v      

       V will contain the values [1,3,3,5,3]

       (2) Suppose one has a wavelength vector W, and three associated flux
       vectors F1, F2, and F3.    Remove all points where a quality vector,
       EPS is negative

               IDL> bad = where( EPS LT 0, Nbad)
               IDL> if Nbad GT 0 then remove, bad, w, f1, f2, f3

 METHOD:
       If more than one element is to be removed, then HISTOGRAM is used
       to generate a 'keep' subscripting vector.    To minimize the length of 
       the subscripting vector, it is only computed between the minimum and 
       maximum values of the index.   Therefore, the slowest case of REMOVE
       is when both the first and last element are removed.

 REVISION HISTORY:
       Written W. Landsman        ST Systems Co.       April 28, 1988
       Cleaned up code          W. Landsman            September, 1992
       Major rewrite for improved speed   W. Landsman    April 2000
       Accept up to 25 variables, use SCOPE_VARFETCH internally
              W. Landsman   Feb 2010
       Fix occasional integer overflow problem  V. Geers  Feb 2011
       Quietly return if index is !null or undefined W.L. Aug 2011

(See $IDLUTILS_DIR/goddard/pro/misc/remove.pro)

REM_DUP

 NAME:	
	REM_DUP
 PURPOSE:  
	Function to remove duplicate values from a vector.

 CALLING SEQUENCE:
	result = rem_dup( a, [ flag ] )

 INPUTS:
	a - vector of values from which duplicates are to be found
	flag - (optional) if supplied then when duplicates occur,
		the one with the largest value of flag is selected.
		If not supplied the the first occurence of the value
		in a is selected.     Should be a vector with the same
               number of elements as a.

 OUTPUT:
	A vector of subscripts in a is returned.  Each subscript
	points to a selected value such that a(rem_dup(a,flag))
	has no duplicates.

 SIDE EFFECTS:
	The returned subscripts will sort the values in a in ascending
	order with duplicates removed.

 EXAMPLES:

	Remove duplicate values in vector a.
	 	a = a[ rem_dup(a)]

	Remove duplicates in vector WAVE.  When duplicate values
	are found, select the one with the largest intensity, INTE.

		sub = rem_dup( wave, inte)
		wave = wave[sub]      
		inte = inte[sub]

 NOTES:
	The UNIQ function in the User's Library uses a faster algorithm,
	but has no equivalent of the "flag" parameter.    Also, note that
       REM_DUP() gives the index of the *first* equal value found, while
       UNIQ() gives the index of the *last* equal value found.

 MODIFICATION HISTORY:
	D. Lindler  Mar. 87
	11/16/90 JKF ACC - converted to IDL Version 2.
	August 1997  -- Changed loop index to type LONG
	October 1997 -- Also changed NGOOD index to LONG
       April 2007 - Use faster algorithm when Flag vector not set, W. Landsman
       Feb 2011 - Remove spurious line W.L.
       Jan 2012 - Call BSORT() to ensure original order maintained for equal
            values

(See $IDLUTILS_DIR/goddard/pro/misc/rem_dup.pro)

REPCHR

 NAME:
       REPCHR
 PURPOSE:
       Replace all occurrences of one character with another in a text string.
 CATEGORY:
 CALLING SEQUENCE:
       new = repchr(old, c1, [c2])
 INPUTS:
       old = original text string.          in
       c1 = character to replace.           in
       c2 = character to replace it with.   in
            default is space.
 KEYWORD PARAMETERS:
 OUTPUTS:
       new = edited string.                 out
 COMMON BLOCKS:
 NOTES:
 MODIFICATION HISTORY:
       R. Sterner.  28 Oct, 1986.
       Johns Hopkins Applied Physics Lab.
       RES 1 Sep, 1989 --- converted to SUN.
       R. Sterner, 27 Jan, 1993 --- dropped reference to array.

 Copyright (C) 1986, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/jhuapl/repchr.pro)

REPSTR

 NAME:
	REPSTR
 PURPOSE:
	Replace all occurences of one substring by another.
 EXPLANATION:
	Meant to emulate the string substitution capabilities of text editors

       For a more sophisticated routine that allows regular expressions look
       at MG_STRREPLACE() 
       http://docs.idldev.com/idllib/strings/mg_streplace.html
 CALLING SEQUENCE:
	result = repstr( obj, in, out )

 INPUT PARAMETERS:
	obj    = object string for editing, scalar or array
	in     = substring of 'obj' to be replaced, scalar 

 OPTIONAL INPUT PARMETER:
	out    = what 'in' is replaced with, scalar.   If not supplied
		then out = '', i.e. 'in' is not replaced by anything. 

 OUTPUT PARAMETERS:
	Result returned as function value.  Input object string
	not changed unless assignment done in calling program.

 PROCEDURE:
	Searches for 'in', splits 'obj' into 3 pieces, reassembles
	with 'out' in place of 'in'.  Repeats until all cases done.

 EXAMPLE:
	If a = 'I am what I am' then print,repstr(a,'am','was')
	will give 'I was what I was'.

 MODIFICATION HISTORY:
	Written by Robert S. Hill, ST Systems Corp., 12 April 1989.
	Accept vector object strings, W. Landsman   HSTX,   April, 1996
       Convert loop to LONG, vectorize STRLEN call W. Landsman June 2002
       Correct bug in optimization, case where STRLEN(OBJ) EQ
         STRLEN(IN), C. Markwardt, Jan 2003
       Fixed problem when multiple replacements extend the string length
                 D. Finkbeiner, W. Landsman  April 2003
       Allow third parameter to be optional again W. Landsman  August 2003
       Remove limitation of 9999 characters, C. Markwardt Dec 2003
       Test for empty "in" string (causing infinite loop) W. Landsman Jan 2010
       Streamline code W Landsman Dec 2011

(See $IDLUTILS_DIR/goddard/pro/misc/repstr.pro)

RESISTANT_MEAN

 NAME:
    RESISTANT_Mean  

 PURPOSE:
    Outlier-resistant determination of the mean and standard deviation. 
 
 EXPLANATION:
    RESISTANT_Mean trims away outliers using the median and the median 
    absolute deviation.    An approximation formula is used to correct for
    the truncation caused by trimming away outliers

 CALLING SEQUENCE:
    RESISTANT_Mean, ARRAY, Sigma_CUT, Mean, Sigma_Mean, Num_RejECTED
                         [/DOUBLE, DIMENSION= , GOODVEC = ]
 INPUT ARGUMENT:
       ARRAY    = Vector or array to average
       Sigma_CUT = Data more than this number of standard deviations from the
               median is ignored. Suggested values: 2.0 and up.

 OUTPUT ARGUMENT:
       Mean  = the mean of the input array, numeric scalar,    If the 
            DIMENSION keyword is set, then MEAN will be an array with one
            less dimension than the input.
 OPTIONAL OUTPUTS:
	Sigma_Mean = the approximate standard deviation of the mean, numeric 
            scalar.  This is the Sigma of the distribution divided by sqrt(N-1)
            where N is the number of unrejected points. The larger
            SIGMA_CUT, the more accurate. It will tend to underestimate the 
            true uncertainty of the mean, and this may become significant for 
            cuts of 2.0 or less. 
       Num_RejECTED = the number of points trimmed, integer scalar
 OPTIONAL INPUT KEYWORDS:
      /DOUBLE - If set, then all calculations are performed internally 
            in double precision.  
      DIMENSION - for a multi-dimensional array, the dimension over which to
            take the mean, starting at 1. If not set, then the scalar mean
            over all elements is used. If this argument is present, the result
            is an array with one less dimension than Array. For example, if 
            the dimensions of Array are N1, N2, N3, and Dimension is 2, then 
            the dimensions of the result are (N1, N3)    
      SUMDIM - Obsolete synonym for DIMENSION
 OPTIONAL OUTPUT KEYWORD:
       Goodvec -  Indices of non-trimmed elements of the input vector
       Wused - synonym for Goodvec (for solarsoft compatibility)
 EXAMPLE:
       IDL> a = randomn(seed, 10000)    ;Normal distribution with 10000 pts
       IDL> RESISTANT_Mean,a, 3, mean, meansig, num    ;3 Sigma clipping    
       IDL> print, mean, meansig,num
 
       The mean should be near 0, and meansig should be near 0.01 ( =
        1/sqrt(10000) ).     
 PROCEDURES USED:
       MEAN() - compute simple mean, in Exelis library
 REVISION HISTORY:
       Written, H. Freudenreich, STX, 1989; Second iteration added 5/91.
       Use MEDIAN(/EVEN)    W. Landsman   April 2002
       Correct conditional test, higher order truncation correction formula
                R. Arendt/W. Landsman   June 2002
       New truncation formula for sigma H. Freudenriech  July 2002
       Divide Sigma_mean by Num_good rather than Npts W. Landsman/A. Conley
                          January 2006
       Use of double precision S. Bianchi February 2008
       More double precision B. Carcich December 2009
       Added DIMENSION keyword (from M. Desnoyer) B. Carcich December 2009
       Use IDL's MEAN() function instead of AVG() W. Landsman Jan 2012

(See $IDLUTILS_DIR/goddard/pro/robust/resistant_mean.pro)

RINTER

 NAME:
      RINTER
 PURPOSE:
      Cubic interpolation of an image at a set of reference points.
 EXPLANATION:
      This interpolation program is equivalent to using the intrinsic 
      INTERPOLATE() function with CUBIC = -0.5.   However,
      RINTER() has two advantages: (1) one can optionally obtain the 
      X and Y derivatives at the reference points, and (2) if repeated
      interpolation is to be applied to an array, then some values can
      be pre-computed and stored in Common.   RINTER() was originally  
      for use with the DAOPHOT procedures, but can also be used for 
      general cubic interpolation.

 CALLING SEQUENCE:
      Z = RINTER( P, X, Y, [ DFDX, DFDY ] )
               or
      Z = RINTER(P, /INIT)

 INPUTS:                 
      P  - Two dimensional data array, 
      X  - Either an N element vector or an N x M element array,
               containing X subscripts where cubic interpolation is desired.
      Y -  Either an N element vector or an N x M element array, 
               containing Y subscripts where cubic interpolation is desired.

 OUTPUT:
      Z -  Result = interpolated vector or array.  If X and Y are vectors,
              then so is Z, but if X and Y are arrays then Z will be also.
              If P is DOUBLE precision, then so is Z, otherwise Z is REAL.

 OPTIONAL OUTPUT:
      DFDX - Vector or Array, (same size and type as Z), containing the 
               derivatives with respect to X
      DFDY - Array containing derivatives with respect to Y

 OPTIONAL KEYWORD INPUT:
     /INIT - Perform computations associated only with the input array (i.e. 
             not with X and Y) and store in common.    This can save time if
             repeated calls to RINTER are made using the same array.  
        
 EXAMPLE:
      suppose P is a 256 x 256 element array and X = FINDGEN(50)/2. + 100.
      and Y = X.  Then Z will be a 50 element array, containing the
      cubic interpolated points.

 SIDE EFFECTS:
      can be time consuming.

 RESTRICTION:
      Interpolation is not possible at positions outside the range of 
       the array (including all negative subscripts), or within 2 pixel
       units of the edge.  No error message is given but values of the 
       output array are meaningless at these positions.

 PROCEDURE:
       invokes CUBIC interpolation algorithm to evaluate each element
       in Z at virtual coordinates contained in X and Y with the data
       in P.                                                          

 COMMON BLOCKS:
       If repeated interpolation of the same array is to occur, then
       one can save time by initializing the common block RINTER.    

 REVISION HISTORY:
       March 1988 written W. Landsman STX Co.
       Checked for IDL Version 2, J. Isensee, September, 1990
       Corrected call to HISTOGRAM, W. Landsman November 1990
       Converted to IDL V5.0   W. Landsman   September 1997
       Fix output derivatives for 2-d inputs, added /INIT W. Landsman May 2000

(See $IDLUTILS_DIR/goddard/pro/image/rinter.pro)

ROBUST_LINEFIT

 NAME:
       ROBUST_LINEFIT

 PURPOSE:
       An outlier-resistant two-variable linear regression. 
 EXPLANATION:
       Either Y on X or, for the case in which there is no true independent 
       variable, the bisecting line of Y vs X and X vs Y is calculated. No 
       knowledge of the errors of the input points is assumed.

 CALLING SEQUENCE:
       COEFF = ROBUST_LINEFIT( X, Y, YFIT, SIG, COEF_SIG, [ /BISECT,
                       BiSquare_Limit = , Close_factor = , NumIT = ] )

 INPUTS:
       X = Independent variable vector, floating-point or double-precision
       Y = Dependent variable vector

 OUTPUTS:
       Function result = coefficient vector. 
       If = 0.0 (scalar), no fit was possible.
       If vector has more than 2 elements (the last=0) then the fit is dubious.

 OPTIONAL OUTPUT PARAMETERS:
       YFIT = Vector of calculated y's
       SIG  = The "standard deviation" of the fit's residuals. If BISECTOR 
               is set, this will be smaller by ~ sqrt(2).
       COEF_SIG  = The estimated standard deviations of the coefficients. If 
               BISECTOR is set, however, this becomes the vector of fit 
               residuals measured orthogonal to the line.

 OPTIONAL INPUT KEYWORDS:
       NUMIT = the number of iterations allowed. Default = 25
       BISECT  if set, the bisector of the "Y vs X" and "X vs Y" fits is 
               determined.  The distance PERPENDICULAR to this line is used 
               in calculating weights. This is better when the uncertainties 
               in X and Y are comparable, so there is no true independent 
               variable.  Bisquare_Limit  Limit used for calculation of 
               bisquare weights. In units of outlier-resistant standard 
               deviations. Default: 6.
               Smaller limit ==>more resistant, less efficient
 Close_Factor  - Factor used to determine when the calculation has converged.
               Convergence if the computed standard deviation changes by less 
               than Close_Factor * ( uncertainty of the std dev of a normal
               distribution ). Default: 0.03.
 SUBROUTINE CALLS:
       ROB_CHECKFIT
       ROBUST_SIGMA, to calculate a robust analog to the std. deviation

 PROCEDURE:
       For the initial estimate, the data is sorted by X and broken into 2
       groups. A line is fitted to the x and y medians of each group.
       Bisquare ("Tukey's Biweight") weights are then calculated, using the 
       a limit of 6 outlier-resistant standard deviations.
       This is done iteratively until the standard deviation changes by less 
       than CLOSE_ENOUGH = CLOSE_FACTOR * {uncertainty of the standard 
               deviation of a normal distribution}

 REVISION HISTORY:
       Written, H. Freudenreich, STX, 4/91.
       4/13/93 to return more realistic SS's HF
       2/94 --more error-checking, changed convergence criterion HF
       5/94 --added BISECT option. HF.
       8/94 --added Close_Factor and Bisquare_Limit options  Jack Saba.
       4/02 --V5.0 version, use MEDIAN(/EVEN)  W. Landsman

(See $IDLUTILS_DIR/goddard/pro/robust/robust_linefit.pro)

ROBUST_POLY_FIT

 NAME:
	ROBUST_POLY_FIT

 PURPOSE:
	An outlier-resistant polynomial fit.

 CALLING SEQUENCE:
	COEFF = ROBUST_POLY_FIT(X,Y,NDEGREE  ,[ YFIT,SIG, /DOULBE, NUMIT=] )

 INPUTS:
	X = Independent variable vector, floating-point or double-precision
	Y = Dependent variable vector
       NDEGREE - integer giving degree of polynomial to fit, maximum = 6
 OUTPUTS:
	Function result = coefficient vector, length NDEGREE+1. 
	IF COEFF=0.0, NO FIT! If N_ELEMENTS(COEFF) > degree+1, the fit is poor
	(in this case the last element of COEFF=0.)
	Either floating point or double precision.

 OPTIONAL OUTPUT PARAMETERS:
	YFIT = Vector of calculated y's
	SIG  = the "standard deviation" of the residuals

 OPTIONAL INPUT KEYWORD:
       /DOUBLE - If set, then force all computations to double precision.
       NUMIT - Maximum number of iterations to perform, default = 25
 RESTRICTIONS:
	Large values of NDEGREE should be avoided. This routine works best
	when the number of points >> NDEGREE.

 PROCEDURE:
	For the initial estimate, the data is sorted by X and broken into 
	NDEGREE+2 sets. The X,Y medians of each set are fitted to a polynomial
	 via POLY_FIT.   Bisquare ("Tukey's Biweight") weights are then 
	calculated, using a limit  of 6 outlier-resistant standard deviations.
	The fit is repeated iteratively until the robust standard deviation of 
	the residuals changes by less than .03xSQRT(.5/(N-1)).

 PROCEDURES CALLED:
        POLY(), POLY_FIT()
       ROB_CHECKFIT()
 REVISION HISTORY
	Written, H. Freudenreich, STX, 8/90. Revised 4/91.
	2/94 -- changed convergence criterion
        Added /DOUBLE keyword, remove POLYFITW call  W. Landsman  Jan 2009

(See $IDLUTILS_DIR/goddard/pro/robust/robust_poly_fit.pro)

ROBUST_SIGMA

 NAME:
	ROBUST_SIGMA  

 PURPOSE:
	Calculate a resistant estimate of the dispersion of a distribution.
 EXPLANATION:
	For an uncontaminated distribution, this is identical to the standard
	deviation.

 CALLING SEQUENCE:
	result = ROBUST_SIGMA( Y, [ /ZERO, GOODVEC = ] )

 INPUT: 
	Y = Vector of quantity for which the dispersion is to be calculated

 OPTIONAL INPUT KEYWORD:
	/ZERO - if set, the dispersion is calculated w.r.t. 0.0 rather than the
		central value of the vector. If Y is a vector of residuals, this
		should be set.

 OPTIONAL OUPTUT KEYWORD:
       GOODVEC = Vector of non-trimmed indices of the input vector
 OUTPUT:
	ROBUST_SIGMA returns the dispersion. In case of failure, returns 
	value of -1.0

 PROCEDURE:
	Use the median absolute deviation as the initial estimate, then weight 
	points using Tukey's Biweight. See, for example, "Understanding Robust
	and Exploratory Data Analysis," by Hoaglin, Mosteller and Tukey, John
	Wiley & Sons, 1983, or equation 9 in Beers et al. (1990, AJ, 100, 32)

 REVSION HISTORY: 
	H. Freudenreich, STX, 8/90
       Replace MED() call with MEDIAN(/EVEN)  W. Landsman   December 2001
       Don't count NaN values  W.Landsman  June 2010

(See $IDLUTILS_DIR/goddard/pro/robust/robust_sigma.pro)

ROB_CHECKFIT

 NAME:
	ROB_CHECKFIT
 PURPOSE:
	Used by ROBUST_... routines to determine the quality of a fit and to
	return biweights.
 CALLING SEQUENCE:
	status = ROB_CHECKFIT( Y, YFIT, EPS, DEL, SIG, FRACDEV, NGOOD, W, B
				BISQUARE_LIMIT = )
 INPUT:
	Y     = the data
	YFIT  = the fit to the data
	EPS   = the "too small" limit
	DEL   = the "close enough" for the fractional median abs. deviations
 RETURNS:
	Integer status. if =1, the fit is considered to have converged

 OUTPUTS:
	SIG   = robust standard deviation analog
	FRACDEV = the fractional median absolute deviation of the residuals
	NGOOD   = the number of input point given non-zero weight in the 
		calculation
	W     = the bisquare weights of Y
	B     = residuals scaled by sigma

 OPTIONAL INPUT KEYWORD:
	BISQUARE_LIMIT = allows changing the bisquare weight limit from 
			default 6.0
 PROCEDURES USED:
       ROBUST_SIGMA()
 REVISION HISTORY:
	Written, H.T. Freudenreich, HSTX, 1/94

(See $IDLUTILS_DIR/goddard/pro/robust/rob_checkfit.pro)

SCALE_VECTOR

 NAME:
       SCALE_VECTOR

 PURPOSE:

       This is a utility routine to scale the elements of a vector
       (or an array) into a given data range. The processed vector
       [MINVALUE > vector < MAXVECTOR] is scaled into the data range
       given by MINRANGE and MAXRANGE.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Utilities

 CALLING SEQUENCE:

       scaledVector = SCALE_VECTOR(vector, [minRange], [maxRange], [MINVALUE=minvalue], [MAXVALUE=maxvalue])

 INPUT POSITIONAL PARAMETERS:

       vector:   The vector (or array) to be scaled. Required.
       minRange: The minimum value of the scaled vector. Set to 0 by default. Optional.
       maxRange: The maximum value of the scaled vector. Set to 1 by default. Optional.

       Note that it is the processed vector [MINVALUE > vector < MAXVALUE] that is
       scaled between minRange and maxRange. See the MINVALUE and MAXVALUE keywords below.

 INPUT KEYWORD PARAMETERS:

       DOUBLE:        Set this keyword to perform scaling in double precision.
                      Otherwise, scaling is done in floating point precision.

       MAXVALUE:      MAXVALUE is set equal to (vector < MAXVALUE) prior to scaling.
                      The default value is MAXVALUE = Max(vector).

       MINVALUE:      MINVALUE is set equal to (vector > MAXVALUE) prior to scaling.
                      The default value is MINXVALUE = Min(vector).

       NAN:           Set this keyword to enable not-a-number checking. NANs
                      in vector will be ignored.

       PRESERVE_TYPE: Set this keyword to preserve the input data type in the output.

 RETURN VALUE:

       scaledVector: The vector (or array) values scaled into the data range.

 COMMON BLOCKS:
       None.

 EXAMPLES:

       x = [3, 5, 0, 10]
       xscaled = SCALE_VECTOR(x, -50, 50)
       Print, xscaled
          -20.0000     0.000000     -50.0000      50.0000

       Suppose your image has a minimum value of -1.7 and a maximum value = 2.5.
       You wish to scale this data into the range 0 to 255, but you want to use
       a diverging color table. Thus, you want to make sure value 0.0 is scaled to 128.
       You proceed like this:

       scaledImage = SCALE_VECTOR(image, 0, 255, MINVALUE=-2.5, MAXVALUE=2.5)

 RESTRICTIONS:

     Requires the following programs from the Coyote Library:

        http://www.idlcoyote.com/programs/convert_to_type.pro
        http://www.idlcoyote.com/programs/fpufix.pro

 MODIFICATION HISTORY:

       Written by:  David W. Fanning, 12 Dec 1998.
       Added MAXVALUE and MINVALUE keywords. 5 Dec 1999. DWF.
       Added NAN keyword. 18 Sept 2000. DWF.
       Removed check that made minRange less than maxRange to allow ranges to be
          reversed on axes, etc. 28 Dec 2003. DWF.
       Added PRESERVE_TYPE and DOUBLE keywords. 19 February 2006. DWF.
       Added FPUFIX to cut down on floating underflow errors. 11 March 2006. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/scale_vector.pro)

SELECT_W

 NAME:
	SELECT_W    
 PURPOSE:
	Create a non-exclusive widget menu of items
 EXPLANATION:
	More than one item may be selected or 'de-selected'.   
	Normally called by SCREEN_SELECT

 CALLING SEQUENCE:
	SELECT_W, items ,iselected, [ comments, command_line, only_one ]

 INPUTS:
	items - string array giving list of items that can be
		selected.

 OPTIONAL INPUTS:
	comments - comments which can be requested for each item in
		array selections.    NOT YET IMPLEMENTED
	command_line - optional command line to be placed at the bottom
		of the screen.  It is usually used to specify what the
		user is selecting.
	only_one - integer flag. If set to 1 then the user can only select
		one item.  The routine returns immediately after the first
		selection is made.
 OPTIONAL KEYWORD INPUT
       SELECTIN - vector of items to be pre-selected upon input (not used for
               only_one option)

 OUTPUT:
	iselected - list of indices in selections giving the selected
		items.

 OPTIONAL OUTPUT KEYWORD:
       COUNT  - Integer scalar giving the number of items selected
 COMMON BLOCKS:
	SELECT_W - Used to communicate with the SELECT_W_EVENT procedure 

 MODIFICATION HISTORY:
	Written, K. Venkatakrishna & W. Landsman, Hughes/STX    January, 1992
	Widgets made MODAL.  M. Greason, Hughes STX, 15 July 1992.
       Changed handling of MODAL keyword for V5.0   W.Thompson  September 1997
       Added selectin keyword  D. Lindler 01/12/99

(See $IDLUTILS_DIR/goddard/pro/misc/select_w.pro)

SETDECOMPOSEDSTATE

Provides a device-independent way to set the color decomposition state of the
current graphics device. Devices that do not have a DECOMPOSED keyword to the
DEVICE command are assumed to be in indexed color mode always.

I have removed the Z-graphics buffer from being controlled by this program. I
do so reluctantly, but I am pragmatic enough to realize that progress forward
is necessarily slow and that I must recognize the reality of legacy IDL code.

My personal view is that all graphics routines should use 24-bit decomposed
color. There are myriad advantages, but basically they boil down to this:
(1) You have 16.7 million colors available to you simultaneously, and (2) you
don't have to contaminate color tables to use drawing colors. Coyote Graphics
routines are in the habit of switching out of whatever color mode the user happens
to be using, into 24-bit decomposed color mode, then switching back when finished
with its business. But, it is impossible to do this correctly in the Z-graphics
buffer.

The reason for this is that in the Z-graphics buffer, you need to switch not only
the color mode, but also the pixel depth. In other words, I would prefer to set
the Z-graphics buffer up like this::

Set_Plot, 'Z'
Device, Decomposed=1, Set_Pixel_Depth=24

But, if I do that, then I need to set it back (for 99 people out of a 100) like this::

Device, Decomposed=0, Set_Pixel_Depth=8

Unfortunately, using this command will erase whatever is in the Z-graphics buffer!

My solution to this problem is to leave it to the user to configure the Z-graphics buffer
the way they want it. If you configure it to use 24-bit decomposed color, all of the Coyote
Graphics routines will work as they normally do. If you configure it to use 8-bit indexed color,
which is the default configuration, then it will work "normally", but you will be in great
danger of contaminating the system color table. The reason for this is that Coyote Graphics
cannot "restore" the entry color table in the Z-buffer without obliterating what is already
in the graphics window. Users who work with indexed color are probably already very much
aware of this problem, so it shouldn't surprise them. (They might not expect this with
Coyote Graphics, but this is the price that has to be paid.)

My suggestion is to put the Z-graphics configuration in your IDL startup file. Set it
up in 24-bit decomposed color mode, use Coyote Graphics to do all your graphical output,
and you will find things working perfectly.
See `Configuring the Z-Graphics Buffer for Coyote Graphics <http://www.idlcoyote.com/cg_tips/configz.php>`
for additional information.

:Categories:
Graphics, Utilities

:Params:
state: in, required, type=integer, default=0
Set to 1 to set the current graphics device to decomposed color. Set to 0
to set the current graphics device to indexed color. Devices lacking a
DECOMPOSED keyword are assumed to be perpetually in indexed color mode.
The Z-graphics buffer is always unchanged after the 24 Dec 2011 update.

:Keywords:
currentstate: out, optional, type=integer
The current decomposition state of the current graphics device when the
program is called. A 1 indicates decomposed color. A 0 indicates indexed
color.
depth: out, optional, type=integer
The currnet pixel depth of the graphics device.
zdepth: in, optional, type=integer
The pixel depth of the Z-graphics device. Set to 8 or 24. Applies ONLY
when setting the Z-graphics device state to 0. If undefined, the current
depth of the Z-graphics device is unchanged from its current state. No
longer used after 24 Dec 2011 update. Code still in place, however.

:Examples:
To set the device in color decomposition mode, then return it, do something like this::

SetDecomposedState, 1, CurrentState=mode
...
SetDecomposeState, mode

:History:
Change History::
Written, 16 November 2010. DWF.
Changes to include SET_PIXEL_DEPTH in Z-graphics buffer. 19 Nov 2010. DWF.
Allow PostScript 7.0 to set the decomposition keyword. 12 Dec 2010. DWF.
Added DEPTH and ZDEPTH keywords. 31 Dec 2010. DWF.
Added a do-nothing NULL device to Case statement. 4 Jan 2011. DWF.
Removed the Z-graphics buffer from control by this program. 24 Dec 2011. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/setdecomposedstate.pro)

SETDEFAULTVALUE

NAME:
SetDefaultValue

PURPOSE:

This procedure sets default values for positional and keyword arguments to
IDL procedures and functions.

AUTHOR:

CATEGORY:

Utilities

CALLING SEQUENCE:

SetDefaultValue, argument, defaultValue

ARGUMENTS:

argument: The augument variable you are setting the default value of. If this variable
is undefined, the defaultValue will be assigned to it. Otherwise, the argument
variable will not change.

defaultValue: The default value that will be assigned to the argument variable ONLY if the argument
variable is undefined. If this variable is undefined, the argument variable will
be treated as if the BOOLEAN keyword had been set.

KEYWORDS:

BOOLEAN: If this keyword is set, the argument value will always be forced to return with a
value of 0 or 1.

EXAMPLE:

FUNCTION Action, arg1, arg2, MULTIPLY=multiply

SetDefaultValue, arg1, 1
SetDefaultValue, arg2, 2
SetDefaultValue, multiply, 1, /BOOLEAN

IF multiply THEN RETURN, arg1 * arg2 ELSE RETURN, arg1 + arg2

END

MODIFICATION HISTORY:

Written by: David W. Fanning, November 26, 2008, from suggestion by Carsten Lechte on
IDL newsgroup on this date.
Made a change to the way the BOOLEAN keyword works. Now argument is set to BOOLEAN before
return, if required. 3 Dec 2008. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/setdefaultvalue.pro)

SIGMA_FILTER

 NAME:
	SIGMA_FILTER
 PURPOSE:
	Replace pixels more than a specified pixels deviant from its neighbors
 EXPLANATION:
	Computes the mean and standard deviation of pixels in a box centered at 
	each pixel of the image, but excluding the center pixel. If the center 
	pixel value exceeds some # of standard deviations from the mean, it is 
	replaced by the mean in box. Note option to process pixels on the edges.
 CALLING SEQUENCE:
	Result = sigma_filter( image, box_width, N_sigma=(#), /ALL,/MON )
 INPUTS:
	image = 2-D image (matrix)
	box_width = width of square filter box, in # pixels (default = 3)
 KEYWORDS:
	N_sigma = # standard deviations to define outliers, floating point,
			recommend > 2, default = 3. For gaussian statistics:
			N_sigma = 1 smooths 35% of pixels, 2 = 5%, 3 = 1%.
	RADIUS = alternative to specify box radius, so box_width = 2*radius+1.
      /ALL_PIXELS causes computation to include edges of image,
      /KEEP causes opposite effect: pixels with values outside of specified
		deviation are not changed, pixels within deviation are smoothed.
      /ITERATE causes sigma_filter to be applied recursively (max = 20 times)
		until no more pixels change (only allowed when N_sigma >= 2).
      /MONITOR prints information about % pixels replaced.
 Optional Outputs:
	N_CHANGE = # of pixels changed (replaced with neighborhood mean).
	VARIANCE = image of pixel neighborhood variances * (N_sigma)^2,
	DEVIATION = image of pixel deviations from neighborhood means, squared.
 CALLS:
	function filter_image( )
 PROCEDURE:
	Compute mean over moving box-cars using smooth, subtract center values,
	compute variance using smooth on deviations from mean,
	check where pixel deviation from mean is within variance of box,
	replace those pixels in smoothed image (mean) with orignal values,
	return the resulting partial mean image.
 MODIFICATION HISTORY:
	Written, 1991, Frank Varosi and Dan Gezari NASA/GSFC
	F.V.1992, added optional keywords /ITER,/MON,VAR=,DEV=,N_CHANGE=.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/image/sigma_filter.pro)

SIGRANGE()

 NAME: 
	SIGRANGE()
 PURPOSE: 
	Selects the most significant data range in an image.
 EXPLANATION: 
	Selects out the most significant range in the data to be used in 
	displaying images.  The histogram of ARRAY is used to select the most
	significant range.      Useful for scaling an image display.
 CALLING SEQUENCE: 
	OUTPUT = SIGRANGE( ARRAY )
 INPUTS: 
	ARRAY	 = Array to take most significant range of.
 OPTIONAL INPUTS: 
	None.
 OUTPUTS: 
	The function returns an array where values above and below the
	selected range are set equal to the maximum and minimum of the
	range respectively.
 OPTIONAL INPUT KEYWORDS: 
	FRACTION = Fraction of data to consider most significant.
		   Defaults to 0.99
	MISSING	 = Value used to flag missing points.  Data points with this
		   value are not considered or changed.
 OPTIONAL OUTPUT KEYWORD
	RANGE    = 2 element vector, giving the range (minimum and maxmimum) 
		used

 NOTES:
       If the image array contains more than 10,000 points then SIGRANGE() 
       uses random indexing of a subset of the points to determine the range
       (for speed).    Thus identical calls to SIGRANGE() might not yield
       identical results (although they should be very close).     
 RESTRICTIONS: 
	ARRAY must have more than two points.  Fraction must be greater than 0 
	and less than 1.

	SIGRANGE was originally part of the SERTS image display package.   
	Other routines from this package are available at 

	http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/image/

	Note that this version of SIGRANGE does not include the non-standard 
	system variables used in the SERTS package.
 REVISION HISTORY: 
	Version 1, William Thompson, GSFC, 12 May 1993.
		Incorporated into CDS library.
	Version 2, William Thompson, GSFC, 25 May 1993.
		Changed call to HISTOGRAM to be compatible with OpenVMS/ALPHA
       Version 3, CDP, RAL, Add RANGE keyword.  16-Apr-96
	Version 4, William Thompson, GSFC, 17 April 1996
		Corrected some problems when range is too high.
	Version 5, 13-Jan-1998, William Thompson, GSFC
		Use random numbers to improve statistics when only using a
		fraction of the array.
	Version 6, 06-Mar-1998, William Thompson, GSFC
		Change default to 0.99

(See $IDLUTILS_DIR/goddard/pro/tv/sigrange.pro)

SIXLIN

 NAME:
       SIXLIN
 PURPOSE:
       Compute linear regression coefficients by six different methods.
 EXPLANATION:
       Adapted from the FORTRAN program (Rev. 1.1)  supplied by Isobe, 
       Feigelson, Akritas, and Babu Ap. J. Vol. 364, p. 104 (1990).   
       Suggested when there is no understanding about the nature of the 
       scatter about a linear relation, and NOT when the errors in the 
       variable are calculable.

 CALLING SEQUENCE:
       SIXLIN, xx, yy, a, siga, b, sigb, [WEIGHT = ]  

 INPUTS:
       XX - vector of X values
       YY - vector of Y values, same number of elements as XX

 OUTPUTS:
       A - Vector of 6 Y intercept coefficients
       SIGA - Vector of standard deviations of 6 Y intercepts
       B - Vector of 6 slope coefficients
       SIGB - Vector of standard deviations of slope coefficients

       The output variables are computed using linear regression for each of 
       the following 6 cases:
               (0) Ordinary Least Squares (OLS) Y vs. X (c.f. linfit.pro)
               (1) Ordinary Least Squares  X vs. Y
               (2) Ordinary Least Squares Bisector
               (3) Orthogonal Reduced Major Axis
               (4) Reduced Major-Axis 
               (5) Mean ordinary Least Squares

 OPTIONAL INPUT KEYWORD:
      WEIGHT -  vector of weights, same number of elements as XX and YY
                For 1 sigma Gausssian errors, the weights are 1/sigma^2 but
                the weight vector can be more general.   Default is no 
                weighting. 
 NOTES:
       Isobe et al. make the following recommendations

       (1) If the different linear regression methods yield similar results
               then quoting OLS(Y|X) is probably the most familiar.

       (2) If the linear relation is to be used to predict Y vs. X then
               OLS(Y|X) should be used.   

       (3) If the goal is to determine the functional relationship between
               X and Y then the OLS bisector is recommended.

 REVISION HISTORY:
       Written   Wayne Landsman          February, 1991         
       Corrected sigma calculations      February, 1992
       Converted to IDL V5.0   W. Landsman   September 1997
       Added WEIGHT keyword   J. Moustakas   Februrary 2007

(See $IDLUTILS_DIR/goddard/pro/math/sixlin.pro)

SIXTY()

 NAME:
	SIXTY()
 PURPOSE:
	Converts a decimal number to sexigesimal.
 EXPLANATION:
	Reverse of the TEN() function.

 CALLING SEQUENCE:
	X = SIXTY( SCALAR, [ /TrailSign ] ) 

 INPUTS:
	SCALAR -- Decimal quantity.  
 OUTPUTS:
	Function value returned = real vector of three elements, 
	sexigesimal equivalent of input decimal quantity.    Double
       precision if the input is double, otherwise floating point.
	By default, a negative number is signified by making the first non-zero
	element of the output vection negative, but this can be modfied with
       the /TrailSign keyword.

 OPTIONAL INPUT KEYWORD:
      /TrailSign - By default, SIXTY() returns a negative sign in the first
         nonzero element.   If /TrailSign is set, then SIXTY() will return
         always return a negative sign in the first element, even if it is
         zero
 PROCEDURE:
	Mostly involves checking arguments and setting the sign.

 EXAMPLE:
	If x = -0.345d then sixty(x) = [0.0, -20.0, 42.0]
                      and sixty(x,/trail) = [-0.0, 20.0, 42.0]
 MODIFICATION HISTORY:
	Written by R. S. Hill, STX, 19-OCT-87         
	Output changed to single precision.  RSH, STX, 1/26/88
	Accept single element vector   W. Landsman   Sep. 1996
	Converted to IDL V5.0   W. Landsman   September 1997
       Added /TrailSign keyword, preserve data type  
                 B. Stecklum/ W. Landsman   March 2006

(See $IDLUTILS_DIR/goddard/pro/astro/sixty.pro)

SKY

 NAME:
       SKY
 PURPOSE:
       Determine the sky level in an image 
 EXPLANATION:
       Approximately 10000 uniformly spaced pixels are selected for the
       computation.  Adapted from the DAOPHOT routine of the same name.

       The sky is computed either by using the procedure mmm.pro (default) 
       or by sigma clipping (if /MEANBACK is set) 

 CALLING SEQUENCE:
       SKY, image, [ skymode, skysig ,/SILENT, /MEANBACK, /NAN, CIRCLERAD= ]
     
         Keywords available  when MEANBACK is not set (passed to mmm.pro): 
                   /DEBUG, HIGHBAD=, /INTEGER, MAXITER=. READNOISE=
         Keywords available when /MEANBACK is set: 
                   CLIPSIG=, /DOUBLE, CONVERGE_NUM=, MAXITER=, /VERBOSE 
 INPUTS:
       IMAGE - One or two dimensional array

 OPTIONAL OUTPUT ARRAYS:
       SKYMODE - Scalar, giving the mode of the sky pixel values of the 
               array IMAGE, as determined by the procedures MMM or MEANCLIP
       SKYSIG -  Scalar, giving standard deviation of sky brightness.   If it
               was not possible to derive a mode then SKYSIG is set to -1

 INPUT KEYWORD PARAMETERS:
	CIRCLERAD - Use this keyword to have SKY only select pixels within
		specified pixel radius of the center of the image.  If 
		CIRCLERAD =1, then the radius is set equal to half the image
		width.   Can only be used with square images.
       /MEANBACK - if set, then the background is computed using the 3 sigma 
             clipped mean (using meanclip.pro) rather than using the mode 
             computed with mmm.pro.    This keyword is useful for the Poisson 
             count regime or where contamination is known  to be minimal.
       /NAN - This keyword must be set to  ignore NaN values when computing 
              the sky.
       /SILENT - If this keyword is supplied and non-zero, then SKY will not
               display the sky value and sigma at the terminal

      The _EXTRA facility can is used to pass optional keywords to the programs
             that actually perform the sky computation: either mmm.pro 
             (default) or meanclip.pro (if /MEANBACK) is set.    The following
             keywords are available with the mmm.pro (default) setting 

       HIGHBAD - scalar value of the (lowest) "bad" pixel level (e.g. cosmic 
                rays or saturated pixels) If not supplied, then there is 
                assumed to be no high bad pixels.
       READNOISE - Scalar giving the read noise (or minimum noise for any 
                pixel).     Normally, MMM determines the (robust) median by 
                averaging the central 20% of the sky values.     In some cases
                where the noise is low, and pixel values are quantized a
                larger fraction may be needed.    By supplying the optional
                read noise parameter, MMM is better able to adjust the
                fraction of pixels used to determine the median. 
       /INTEGER - Set this keyword if the  input SKY image only contains
                discrete integer values.    This keyword is only needed if the
                SKY image is of type float or double precision, but contains 
                only discrete integer values.     

     If the /MEANBACK keyword is set then the following keywords are available

       CLIPSIG:  Number of sigma at which to clip.  Default=3
	MAXITER:  Ceiling on number of clipping iterations.  Default=5
       CONVERGE_NUM:  If the proportion of rejected pixels is less
           than this fraction, the iterations stop.  Default=0.02, i.e.,
           iteration stops if fewer than 2% of pixels excluded.
       /DOUBLE - if set then perform all computations in double precision.
                 Otherwise double precision is used only if the input
                 data is double

 PROCEDURE:
       A grid of points, not exceeding 10000 in number, is extracted
       from the srray.  The mode of these pixel values is determined
       by the procedure mmm.pro or meanclip.pro.   In a 2-d array the grid is 
       staggered in each row to avoid emphasizing possible bad columns

 PROCEDURE CALLS:
       MEANCLIP, MMM, DIST_CIRCLE
 REVISION HISTORY:
       Written, W. Landsman   STX Co.            September, 1987     
       Changed INDGEN to LINDGEN                 January, 1994
       Fixed display of # of points used         March, 1994
       Stagger beginning pixel in each row, added NSKY, READNOISE, HIGHBAD
          W. Landsman        June 2004
      Adjustments for unbiased sampling  W. Landsman June 2004
      Added /NAN keyword, put back CIRCLERAD keyword W. Landsman July 2004
      Added MEANBACK keyword, _EXTRA kewyord ,preserve data type in 
             calculations       W. Landsman November 2005
      Fix problem for very large images by requiring at least 2 pixels to
       be sampled per row.    March 2007    W. Landsman
      Avoid possible out of bounds if /NAN set   W. Landsman   Jan 2008
      Use  TOTAL(/INTEGER)      June 2009

(See $IDLUTILS_DIR/goddard/pro/idlphot/sky.pro)

SKYADJ_CUBE

 NAME:                    
        SKYADJ_CUBE

 PURPOSE:
       Sky adjust the planes of a datacube.

 EXPLANATION:
       When removing cosmic rays from a set of images, it is desirable that
       all images have the same sky level.    This procedure (called by
       CR_REJECT) removes the sky from each image in a data cube.    

 CALLING SEQUENCE:
       SKYADJ_CUBE,Datacube,Skyvals,Totsky

 MODIFIED ARGUMENT:
       Datacube:  3-D array with one image of same field in each plane.
                  Returned with sky in each plane adjusted to zero.

 OUTPUT ARGUMENTS:
       Skyvals:   Array of sky values used on each plane of datacube.
                  For a scalar sky, this parameter is a vector
                  containing the sky value for each image plane.  For a
                  vector sky, this parameter is a 2-D array where each
                  line corresponds to one image plane.

 INPUT KEYWORD PARAMETERS:

       REGION   - [X0,X1,Y0,Y1] to restrict area used for computation
                  of sky.  Default is 0.1*Xdim, 0.9*Xdim, 0.1*Ydim,
                  0.9*Ydim.  If INPUT_MASK is specified, the two 
                  specs are combined, i.e., the intersection of the
                  areas is used.
       VERBOSE  - Flag.  If set, print information on skyvals.
       NOEDIT   - Flag.  If set, return sky values without changing
                  datacube.
       XMEDSKY  - Flag.  If set, return vector sky as a function of X.
       SELECT   - Array of subscripts of planes of the cube to process.
                  (Default=all)
       EXTRAPR  - Applies only in XMEDSKY mode.
                  Subregion to use for polynomial extrapolation of sky
                  vector into portions excluded by REGION parameter.
                  (Default=first and last 10% of pixels; set to zero
                  to defeat extrapolation)
       EDEGREE  - Applies only in XMEDSKY mode.  
                  Degree of polynomial for extrapolation (Default=1)
       INPUT_MASK - Cube of flags corresponding to data cube.  If used,
                  the sky computation is restricted to the smallest 
                  contiguous rectangle containing all the pixels flagged
                  valid (with 1 rather than 0).

 PROCEDURE:
       Uses astronomy library "sky" routine for scalar sky and
       column-by-column median for vector sky.

 MODIFICATION HISTORY:
   10 Jul. 1997   - Written.  R. S. Hill, Hughes STX
   20 Oct. 1997   - 1-D sky option.  RSH
    7 Aug. 1998   - SELECT keyword.  RSH
    6 Oct. 1998   - Extrapolation.  RSH
    7 Oct. 1998   - INPUT_MASK added.  RSH
   21 Oct. 1998   - Fallback to 3-sigma clipped mean if mode fails.  RSH
   22 Mar. 2000   - Combine mask with region rather having mask
                    override region.  Improve comments.  RSH
   16 June 2000   - On_error and message used.  Square brackets for array 
                    subscripts.  EXTRAP included in this file.  
                    WBL & RSH, 16 June 2000

(See $IDLUTILS_DIR/goddard/pro/image/skyadj_cube.pro)

SPEC_DIR()

 NAME:
     SPEC_DIR()
 PURPOSE:
     Complete a file specification by appending the default disk or directory

 CALLING SEQUENCE:                      
     File_spec = SPEC_DIR( filename, [ extension ] )
 INPUT:
     filename - character string giving partial specification of a file
               name.  Examples for different operating systems include the
                       following:
               Unix: 'pro/test.dat', '$IDL_HOME/test','~/subpro'
               MacOS: ':Programs:test'
               Windows: '\pro\test.dat','d:\pro\test'

 OPTIONAL INPUT:
     exten - string giving a default file name extension to be used if
             filename does not contain one.  Do not include the period.

 OUTPUT:
     File_spec - Complete file specification using default disk or 
               directory when necessary.  

 EXAMPLE:
      IDL> a = spec_dir('test','dat')

      is equivalent to the commands
      IDL> cd, current=cdir
      IDL> a = cdir + delim + 'test.dat'

      where delim is the OS-dependent separator 
 METHOD:
      SPEC_DIR() decomposes the file name using FDECOMP, and appends the 
      default directory (obtained from the FILE_EXPAND_PATH) if necessary.   

      SPEC_DIR() does not check whether the constructed file name actually
      exists.
 PROCEDURES CALLED:
      FDECOMP, EXPAND_TILDE()
 REVISION HISTORY:
      Written W. Landsman         STX         July, 1987
      Expand Unix tilde if necessary              W. Landsman  September 1997
      Assume since V5.5, use FILE_EXPAND_PATH, remove VMS support        
              W. Landsman   September 2006

(See $IDLUTILS_DIR/goddard/pro/misc/spec_dir.pro)

SPHDIST

 NAME:
       SPHDIST
 PURPOSE:
       Angular distance between points on a sphere.
 CALLING SEQUENCE:
       d = sphdist(long1, lat1, long2, lat2)
 INPUTS:
       long1 = longitude of point 1, scalar or vector
       lat1 = latitude of point 1, scalar or vector
       long2 = longitude of point 2, scalar or vector
       lat2 = latitude of point 2, scalar or vector

 OPTIONAL KEYWORD INPUT PARAMETERS:
       /DEGREES - means angles are in degrees, else radians.
 OUTPUTS:
       d = angular distance between points (in radians unless /DEGREES
           is set.)
 PROCEDURES CALLED:
       RECPOL, POLREC
 NOTES:
       (1) The procedure GCIRC is similar to SPHDIST(), but may be more 
           suitable for astronomical applications.

       (2) If long1,lat1 are scalars, and long2,lat2 are vectors, then
           SPHDIST returns a vector giving the distance of each element of 
           long2,lat2 to long1,lat1.   Similarly, if long1,lat1 are vectors,
           and long2, lat2 are scalars, then SPHDIST returns a vector giving
           giving the distance of each element of long1,lat1 to to long2,lat2. 
           If both long1,lat1 and long2,lat2 are vectors then SPHDIST returns
           vector giving the distance of each element of long1,lat1 to the 
           corresponding element of long2, lat2.   If the input vectors are 
           not of equal length, then excess elements of the longer ones will 
           be ignored.
 MODIFICATION HISTORY:
       R. Sterner, 5 Feb, 1991
       R. Sterner, 26 Feb, 1991 --- Renamed from sphere_dist.pro

 Copyright (C) 1991, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/jhuapl/sphdist.pro)

SRCOR

 NAME:
       SRCOR
 PURPOSE:
       Correlate the source positions found on two lists.

 EXPLANATION:
       Source matching is done by finding sources within a specified radius.
       If you have position errors available and wish to match by significance
       level, then try match_xy.pro in the TARA library 
      (http://www.astro.psu.edu/xray/docs/TARA/)

 CALLING SEQUENCE:
       srcor,x1in,ylin,x2in,y2in,dcr,ind1,ind2,
                         [MAGNITUDE=,SPHERICAL=,COUNT=,/SILENT]
 INPUTS:
       x1in,y1in - First set of x and y coordinates.  The program
                   marches through this list element by element,
                   looking in list 2 for the closest match.  So, the program
                   will run faster if this is the shorter of the two lists.
                   Unless you use the option or magnitude keyword, there is
                   nothing to guarantee unique matches.  
       x2in,y2in - Second set of x and y coordinates.  This list is
                   searched in its entirety every time one element of list 1
                   is processed.
       dcr - Critical radius outside which correlations are rejected;
             but see 'option' below.
 OPTIONAL KEYWORD INPUT:
       option - Changes behavior of program and description of output
                lists slightly, as follows: 
       OPTION=0 or left out
             Same as older versions of SRCOR.  The closest match from list2
             is found for each element of list 1, but if the distance is
             greater than DCR, the match is thrown out.  Thus the index
             of that element within list 1 will not appear in the IND1 output
             array.
       OPTION=1
             Forces the output mapping to be one-to-one.  OPTION=0 results,
             in general, in a many-to-one mapping from list 1 to list 2.
             Under OPTION=1, a further processing step is performed to
             keep only the minimum-distance match, whenever an entry from
             list 1 appears more than once in the initial mapping.
       OPTION=2
             Same as OPTION=1, except the critical distance parameter DCR
             is ignored.  I.e., the closest object is retrieved from list 2
             for each object in list 1 WITHOUT a critical-radius criterion,
             then the clean-up of duplicates is done as under OPTION=1.
       magnitude
             An array of stellar magnitudes corresponding to x1in and y1in.  
             If this is supplied, then the brightest star from list 1
             within the selected distance of the star in list 2 is taken.
             The option keyword is ignored in this case.
       spherical
             If SPHERICAL=1, it is assumed that the input arrays are in
             celestial coordinates (RA and Dec), with x1in and x2in in
             decimal hours and y1in and y2in in decimal degrees.  If
             SPHERICAL=2 then it is assumed that the input arrays are in
             longitude and latitude with x1in,x2in,y1in,y2in in decimal
             degrees.  In both cases, the critial radius dcr is in
             *arcseconds*.  Calculations of spherical distances are made
             with the gcirc program.
 OUTPUTS:
       ind1 - index of matched stars in first list, set to -1 if no matches
              found
       ind2 - index of matched stars in second list
 OPTIONAL OUTPUT KEYWORD:
       Count - integer giving number of matches returned
 PROCEDURES USED:
       GCIRC, REMOVE
 REVISON HISTORY:
       Adapted from UIT procedure  J.Wm.Parker, SwRI 29 July 1997
       Improve speed for spherical searches, added /SILENT keyword  
                               W. Landsman  Mar 2009
       Avoid error when no matches found with /SPHERICAL  O. Trottier June 2009
       Added output Count keyword     W.L   June 2009
       Adjust right ascension for cosine angle W.L. December 2009
       Return as soon as no matches found W.L.  December 2009
       Use some V6.0 notation  W.L.   February 2011
       Fix problem when /Spherical and Option =2 set, and sources separated
          by more han 180 degrees.   W.L.  March 2011

(See $IDLUTILS_DIR/goddard/pro/idlphot/srcor.pro)

STARAST

 NAME:
       STARAST 
 PURPOSE:
       Compute astrometric solution using positions of 2 or 3 reference stars
 EXPLANATION:
       Computes an exact astrometric solution using the positions and 
       coordinates from 2 or 3 reference stars and assuming a tangent 
       (gnomonic) projection.   If 2 stars are used, then
       the X and Y plate scales are assumed to be identical, and the
       axis are assumed to be orthogonal.   Use of three stars will
       allow a unique determination of each element of the CD matrix.

 CALLING SEQUENCE:
       starast, ra, dec, x, y, cd, [/Righthanded, HDR = h, PROJECTION=]

 INPUTS:
       RA - 2 or 3 element vector containing the Right Ascension in DEGREES
       DEC- 2 or 3 element vector containing the Declination in DEGREES
       X -  2 or 3 element vector giving the X position of reference stars
       Y -  2 or 3 element vector giving the Y position of reference stars
 OUTPUTS:
       CD - CD (Coordinate Description) matrix (DEGREES/PIXEL) determined 
               from stellar positions and coordinates.
 OPTIONAL INPUT KEYWORD:
       /RightHanded - If only 2 stars are supplied, then there is an ambiguity
               in the orientation of the coordinate system.   By default,
               STARAST assumes the astronomical standard left-handed system
               (R.A. increase to the left).   If /Right is set then a 
               righthanded coordinate is assumed.  This keyword has no effect
               if 3 star positions are supplied.
        PROJECTION - Either a 3 letter scalar string giving the projection
               type (e.g. 'TAN' or 'SIN') or an integer 1 - 25 specifying the
               projection as given in the WCSSPH2XY procedure.   If not 
               specified then a tangent projection is computed.
 OPTIONAL INPUT-OUTPUT KEYWORD:
        HDR - If a FITS header string array is supplied, then an astrometry 
              solution is added to the header using the CD matrix and star 0
              as the reference pixel (see example).   Equinox 2000 is assumed.
 EXAMPLE:
        To use STARAST to add astrometry to a FITS header H;

        IDL> starast,ra,dec,x,y,cd       ;Determine CD matrix
        IDL> crval = [ra[0],dec[0]]      ;Use Star 0 as reference star
        IDL> crpix = [x[0],y[0]] +1      ;FITS is offset 1 pixel from IDL
        IDL> putast,H,cd,crpix,crval     ;Add parameters to header

        This is equivalent to the following command:
        IDL> STARAST,ra,dec,x,y,hdr=h      
  
 METHOD:
       The CD parameters are determined by solving the linear set of equations
       relating position to local coordinates (l,m)

       For highest accuracy the first star position should be the one closest
       to the reference pixel.
 REVISION HISTORY:
       Written, W. Landsman             January 1988
       Converted to IDL V5.0   W. Landsman   September 1997
       Added /RightHanded and HDR keywords   W. Landsman   September 2000
       Write CTYPE values into header   W. Landsman/A. Surkov  December 2002
       CD matrix was mistakenly transpose in 3 star solution
       Added projection keyword    W. Landsman   September 2003
       Test for singular matrix W. Landsman  August 2011

(See $IDLUTILS_DIR/goddard/pro/astrom/starast.pro)

STORE_ARRAY

 NAME:
	STORE_ARRAY
 PURPOSE:
	Insert array INSERT into the array DESTINATION
 EXPLANATION:
	The dimensions of the DESTINATION array are adjusted to accommodate
	the inserted array.
 CATEGOBY:
	Utility
 CALLING SEQUENCE:
	STORE_ARRAY, DESTINATION, INSERT, INDEX
 INPUT:
	DESTINATION	= Array to be expanded.
	INSERT		= Array to insert into DESTINATION.
	INDEX		= Index of the final dimension of DESTINATION to insert
			  INSERT into.
 OUTPUTS:
	DESTINATION	= Expanded output array.  If both input arrays have the
			  same number of dimensions, then the DESTINATION will
			  be replaced with INSERT.
 RESTRICTIONS:
	DESTINATION and INSERT have to be either both of type string or both of
	numerical types.

	INSERT must not have more dimensions than DESTINATION.

 MODIFICATION HISTOBY:
	William Thompson, Feb. 1992, from BOOST_ARRAY by D. Zarro and P. Hick.
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/store_array.pro)

STRCOMPRESS2

 NAME:
	STRCOMPRESS2
 PURPOSE:
	Remove blanks around specified characters in a string
 CALLING SEQUENCE
	newstring = strcompress2( st, chars)
 INPUTS:
       st - any scalar string
      chars - scalar  or vector string specifing which characters around which 
             blanks should be removed.    For example, if chars=['=','-','+'] 
              then spaces around the three characters "=', '-', and '+' will 
             be removed.
 OUTPUTS:
       newstring - input string with spaces removed around the specified 
        characters.   
 EXAMPLE:
       The Vizier constraint string (see queryvizier.pro) does not allow 
       blanks around the operators '=','<', or '>'.     But we do not want
       to remove blanks around names (e.g. 'NGC 5342'):
 
       IDL> st = 'name = NGC 5342, v< 23'
       IDL> print,strcompress2(st, ['=','<','>'])
            name=NGC 5342, v<23
 MODIFICATION HISTORY:
	Written by W.Landsman                   July 2008

(See $IDLUTILS_DIR/goddard/pro/misc/strcompress2.pro)

STRN

 NAME:
	STRN
 PURPOSE:
	Convert a number to a string and remove padded blanks.
 EXPLANATION:
	The main and original purpose of this procedure is to convert a number
	to an unpadded string (i.e. with no blanks around it.)  However, it 
	has been expanded to be a multi-purpose formatting tool.  You may 
	specify a length for the output string; the returned string is either 
	set to that length or padded to be that length.  You may specify 
	characters to be used in padding and which side to be padded.  Finally,
	you may also specify a format for the number.  NOTE that the input 
	"number" need not be a number; it may be a string, or anything.  It is
	converted to string.

 CALLING SEQEUNCE:
	tmp = STRN( number, [ LENGTH=, PADTYPE=, PADCHAR=, FORMAT = ] )

 INPUT:
	NUMBER    This is the input variable to be operated on.  Traditionally,
		 it was a number, but it may be any scalar type.

 OPTIONAL INPUT:
	LENGTH    This KEYWORD specifies the length of the returned string.  
		If the output would have been longer, it is truncated.  If 
		the output would have been shorter, it is padded to the right 
		length.
	PADTYPE   This KEYWORD specifies the type of padding to be used, if any.
		0=Padded at End, 1=Padded at front, 2=Centered (pad front/end)
		IF not specified, PADTYPE=1
	PADCHAR   This KEYWORD specifies the character to be used when padding.
		The default is a space (' ').
	FORMAT    This keyword allows the FORTRAN type formatting of the input
		number (e.g. '(f6.2)')

 OUTPUT:
	tmp       The formatted string

 USEFUL EXAMPLES:
	print,'Used ',strn(stars),' stars.'  ==> 'Used 22 stars.'
	print,'Attempted ',strn(ret,leng=6,padt=1,padch='0'),' retries.'
		==> 'Attempted 000043 retries.'
	print,strn('M81 Star List',length=80,padtype=2)
		==> an 80 character line with 'M81 Star List' centered.
	print,'Error: ',strn(err,format='(f15.2)')
		==> 'Error: 3.24'     or ==> 'Error: 323535.22'

 HISTORY:
	03-JUL-90 Version 1 written by Eric W. Deutsch
	10-JUL-90 Trimming and padding options added         (E. Deutsch)
	29-JUL-91 Changed to keywords and header spiffed up     (E. Deutsch)
	Ma7 92 Work correctly for byte values (W. Landsman)
	19-NOV-92 Added Patch to work around IDL 2.4.0 bug which caused an
	error when STRN('(123)') was encountered.            (E. Deutsch)
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/strn.pro)

STRNUMBER()

 NAME:
      STRNUMBER()
 PURPOSE:
      Function to determine if a string is a valid numeric value.

 EXPLANATION:
      A string is considered a valid numeric value if IDL can convert it
      to a numeric variable without error.    
 CALLING SEQUENCE:
      result = strnumber( st, [val, /HEX] )

 INPUTS:
      st - any IDL scalar string

 OUTPUTS:
      1 is returned as the function value if the string st has a
      valid numeric value, otherwise, 0 is returned.

 OPTIONAL OUTPUT:
      val - (optional) value of the string. double precision unless /L64 is set

 OPTIONAL INPUT KEYWORD:
       /HEX - If present and nonzero, the string is treated as a hexadecimal
             longword integer.
       /L64 - If present and nonzero, the val output variable is returned
              as a 64 bit integer.    This to ensure that precision is not       
              lost when returning a large 64 bit integer as double precision.
              This keyword has no effect on the function result.
       /NAN - if set, then the value of an empty string is returned as NaN,
              by default the returned value is 0.0d.     In either case,
              an empty string is considered a valid numeric value.

 EXAMPLES:
      IDL> res = strnumber('0.2d', val)
           returns res=1 (a valid number), and val = 0.2000d
              
 NOTES:
      (1) STRNUMBER was modified in August 2006 so that an empty string is 
      considered a valid number.   Earlier versions of strnumber.pro did not 
      do this because in very early (pre-V4.0) versions of IDL
      this could corrupt the IDL session.

       (2) STRNUMBER will return a string such as '23.45uyrg' as a valid 
      number (=23.45) since this is how IDL performs the type conversion.  If
      you want a stricter definition of valid number then use the VALID_NUM()
      function.
 HISTORY:
      version 1  By D. Lindler Aug. 1987
      test for empty string, W. Landsman          February, 1993
      Hex keyword added.  MRG, RITSS, 15 March 2000.
      An empty string is a valid number   W. Landsman    August 2006
      Added /NAN keyword  W. Landsman August 2006
      Added /L64 keyword W. Landsman  Feb 2010

(See $IDLUTILS_DIR/goddard/pro/misc/strnumber.pro)

STR_INDEX()

 NAME:
       STR_INDEX()

 PURPOSE:
       Get indices of a substring (SUBSTR) in string.

 EXPLANATION:
       The IDL intrinsic function STRPOS returns only the index of the first
       occurrence of a substring. This routine calls itself recursively to get
       indices of the remaining occurrences.

 CALLING SEQUENCE:
       result= STR_INDEX(str, substr [, offset])

 INPUTS:
       STR    -- The string in which the substring is searched for
       SUBSTR -- The substring to be searched for within STR

 OPTIONAL INPUTS:
       OFFSET -- The character position at which the search is begun. If
                 omitted or being negative, the search begins at the first
                 character (character position 0).

 OUTPUTS:
       RESULT -- Integer scalar or vector containing the indices of SUBSTR
                 within STR. If no substring is found, it is -1.

 CALLS:
       DELVARX

 COMMON BLOCKS:
       STR_INDEX -- internal common block. The variable save in the block is
                    deleted upon final exit of this routine.

 CATEGORY:
       Utility, string

 MODIFICATION HISTORY:
       Written January 3, 1995, Liyun Wang, GSFC/ARC
       Converted to IDL V5.0   W. Landsman   September 1997
       Use size(/TNAME) instead of DATATYPE()   W. Landsman   October 2001

(See $IDLUTILS_DIR/goddard/pro/misc/str_index.pro)

STR_SIZE

 NAME:
  STR_SIZE

 PURPOSE:

  The purpose of this function is to return the proper
  character size to make a specified string a specifed
  width in a window. The width is specified in normalized
  coordinates. The function is extremely useful for sizing
  strings and labels in resizeable graphics windows.

 AUTHOR:

   FANNING SOFTWARE CONSULTING
   David Fanning, Ph.D.
   1645 Sheely Drive
   Fort Collins, CO 80526 USA
   Phone: 970-221-0438
   E-mail: david@idlcoyote.com
   Coyote's Guide to IDL Programming: http://www.idlcoyote.com/

 CATEGORY:

  Graphics Programs, Widgets.

 CALLING SEQUENCE:

  thisCharSize = STR_SIZE(thisSting, targetWidth)

 INPUTS:

  thisString:  This is the string that you want to make a specifed
     target size or width.

 OPTIONAL INPUTS:

  targetWidth:  This is the target width of the string in normalized
     coordinates in the current graphics window. The character
     size of the string (returned as thisCharSize) will be
     calculated to get the string width as close as possible to
     the target width. The default is 0.25.

 KEYWORD PARAMETERS:

  INITSIZE:  This is the initial size of the string. Default is 1.0.

  STEP:   This is the amount the string size will change in each step
     of the interative process of calculating the string size.
     The default value is 0.05.

  XPOS:   X position of the output test string. This can be
     used on the Postscript device, where no pixmap windows are
     available and where therefore the test strings would appear on
     the printable area. Default is 0.5 on most devices. If !D.NAME
     is PS, the default is 2.0 to draw the test string out of the
     drawable window area.

  YPOS:   Y position of the output test string. This can be
     used on the Postscript device, where no pixmap windows are
     available and where therefore the test strings would appear on
     the printable area. Default is 0.5 on most devices. If !D.NAME
     is PS, the default is 2.0 to draw the test string out of the
     drawable window area.

 OUTPUTS:

  thisCharSize:  This is the size the specified string should be set
     to if you want to produce output of the specified target
     width. The value is in standard character size units where
     1.0 is the standard character size.

 EXAMPLE:

  To make the string "Happy Holidays" take up 30% of the width of
  the current graphics window, type this:

      XYOUTS, 0.5, 0.5, ALIGN=0.5, "Happy Holidays", $
        CHARSIZE=STR_SIZE("Happy Holidays", 0.3)

 MODIFICATION HISTORY:

  Written by: David Fanning, 17 DEC 96.
  Added a scaling factor to take into account the aspect ratio
     of the window in determing the character size. 28 Oct 97. DWF
  Added check to be sure hardware fonts are not selected. 29 April 2000. DWF.
  Added a pixmap to get proper scaling in skinny windows. 16 May 2000. DWF.
  Forgot I can't do pixmaps in all devices. :-( Fixed. 7 Aug 2000. DWF.
  Added support of PostScript at behest of Benjamin Hornberger. 11 November 2004. DWF.
  Cleaned up the code a bit. 28 Feb 2011. DWF.
  Fixed non-square window algorithm to reflect my original intentions. 10 June 2011.

(See $IDLUTILS_DIR/goddard/pro/coyote/str_size.pro)

ST_DISKREAD

 NAME: 
       ST_DISKREAD

 PURPOSE:  
       Read HST FITS formatted disk files and reconstruct GEIS (STSDAS) files.

 CALLING SEQUENCE:  
       ST_DISKREAD, infiles

 INPUT PARAMETER:
       infiles - (scalar string) input disk files to be converted into GEIS
                       files. Wildcards are allowed.
 FILES CREATED:

   GEIS files:
         The GEIS file is reconstructed from each input Fits file. The 
       output filename is composed from the rootname of the observation
       and the appropriate GEIS file extension (i.e. d0h/d, c0h/d, etc.).
   Tables:
         If input file is a fits table, the output is an SDAS table.

 EXAMPLES:
       a) Reconstruct the GEIS file for disk FITS file z29i020ct*.fits.
               st_diskread,'z29i020ct*.fits'

 PROCEDURES CALLED:
       ST_DISK_DATA, ST_DISK_TABLE, ST_DISK_GEIS
       FTSIZE,SXPAR(),TAB_CREATE, TAB_WRITE
 HISTORY: 
       10/17/94        JKF/ACC - taken from ST_TAPEREAD.
       11/02/94        JKF/ACC - added /block on open statement to
                                 handle files with 512 bytes/record.
       12/6/95         JKF/ACC - include new jitter files...replaces
                                               st_read_jitter.pro.
       03/5/96         W. Landsman, change FORRD to READU, remove Version 1
                               type codes, add message facility
       05/20/00        W. Landsman, remove obsolete !ERR calls, new calling
                               sequence to FTINFO
       09/2006        W. Landsman, remove obsolete keywords to OPEN

****************************************************************************
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/st_diskread.pro)

ST_DISK_DATA

 NAME:
       ST_DISK_DATA 

 PURPOSE:
       Routine to read next header and data array from an HST FITS disk file.
       This is a subroutine of ST_DISKREAD and not intended for stand alone 
       use.

CALLING SEQUENCE:
       st_disk_data,unit,h,data,name,gcount,dimen,opsize,nbytes,itype

INPUTS:
       unit - logical unit number.

OUTPUTS:
       h - FITS header
       data - data array
       name - file name
       gcount - number of groups
       dimen - data dimensions
       opsize - parameter blocks size
       nbytes - bytes per data group
       itype - idl data type

 Notes:
       This is not a standalone program. Use ST_DISKREAD.

 PROCEDURES CALLED:
       GETTOK(), SXPAR()
 HISTORY:
       10/17/94        JKF/ACC         - taken from ST_TAPE_DATA.

***************************************************************************

(See $IDLUTILS_DIR/goddard/pro/sdas/st_diskread.pro)

ST_DISK_GEIS

 NAME:
       ST_DISK_GEIS 

 PURPOSE:
        Routine to construct GEIS files from ST FITS disk files.

 CALLING SEQUENCE:
       ST_DISK_GEIS, h, data, htab, tab, table_available, name, gcount, 
               dimen,opsize, nbytes_g,itype

 INPUT PARAMETERS:
       h - header for data
       data - data array
       htab - header for the table
       tab - fits table
       table_available - logical variable (1 if table was found)
       name - data set name
       gcount - number of groups
       dimen - data dimensions
       opsize - original parameter block size
       nbytes_g - number of bytes per group
       itype - idl integer data type value for the output data groups

 SIDE EFFECTS:

       GEIS file updated with group parameters in unit 1 (already open)
       and header file created

 NOTES:
       This is not a standalone program. Use st_diskread.

       During the creation of the header, this routine performs the 
       following steps:
       1) create a basic fits header (7 keywords)
       2) adjust basic fits header for the number of axis present (i.e. >1)
       3) adjust basic fits header for parameter keywords (i.e. ptype,etc)
       4) from this point, sequentially copies keywords until it hits one of
               the following keywords 'INSTRUME','INSTRUID', or 'CONFG'.
       5) append 'END' statement

 PROCEDURES CALLED:
       FTSIZE, SXADDPAR, SXHWRITE
 HISTORY:
       10/17/94        JKF/ACC         - taken from ST_DISK_GEIS

****************************************************************************

(See $IDLUTILS_DIR/goddard/pro/sdas/st_diskread.pro)

ST_DISK_TABLE

NAME:
       ST_DISK_TABLE 

 PURPOSE:
       Routine to read FITS table from an ST fits on disk.
       This is a subroutine of st_diskread and not intended for stand alone 
       use.

 CALLING SEQUENCE:
       st_disk_table,unit,h,data

 INPUTS PARAMETER:
       unit - disk unit number


 OUTPUTS:
       h - FITS header
       data - table array

 NOTES:
       This is not a standalone program. Use ST_DISKREAD.
          
 HISTORY:
       10/17/94        JKF/ACC - taken from ST_TAPE_TABLE.
       12/7/95         JKF/ACC - handle tables for jitter data.
                                            
****************************************************************************

(See $IDLUTILS_DIR/goddard/pro/sdas/st_diskread.pro)

SUBSTAR

 NAME:
	SUBSTAR
 PURPOSE:
	Subtract a scaled point spread function at specified star position(s).
 EXPLANATION:
	Part of the IDL-DAOPHOT photometry sequence

 CALLING SEQUENCE:
	SUBSTAR, image, x, y, mag, [ id, psfname, /VERBOSE] 

 INPUT-OUTPUT:
	IMAGE -  On input, IMAGE is the original image array.  A scaled
		PSF will be subtracted from IMAGE at specified star positions.
		Make a copy of IMAGE before calling SUBSTAR, if you want to
		keep a copy of the unsubtracted image array

 INPUTS:
	X -   REAL Vector of X positions found by NSTAR (or FIND)
	Y -   REAL Vector of Y positions found by NSTAR (or FIND)        
	MAG - REAL Vector of stellar magnitudes found by NSTAR (or APER)
		Used to scale the PSF to match intensity at star position.
		Stars with magnitude values of 0.0 are assumed missing and 
		ignored in the subtraction.

 OPTIONAL INPUTS:
	ID -  Index vector indicating which stars are to be subtracted.  If
		omitted, (or set equal to -1), then stars will be subtracted 
		at all positions specified by the X and Y vectors.

	PSFNAME - Name of the FITS file containing the PSF residuals, as
		generated by GETPSF.  SUBSTAR will prompt for this parameter
		if not supplied.      

 OPTIONAL INPUT KEYWORD:
	VERBOSE - If this keyword is set and nonzero, then SUBSTAR will 
		display the star that it is currently processing      

 COMMON BLOCKS:
	The RINTER common block is used (see RINTER.PRO) to save time in the
	PSF calculations

 PROCEDURES CALLED:
	DAO_VALUE(), READFITS(), REMOVE, SXOPEN, SXPAR(), SXREAD()
 REVISION HISTORY:
	Written, W. Landsman                      August, 1988
	Added VERBOSE keyword                     January, 1992
	Fix star subtraction near edges, W. Landsman    May, 1996
	Assume the PSF file is in FITS format  W. Landsman   July, 1997
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/idlphot/substar.pro)

SUNPOS

 NAME:
       SUNPOS
 PURPOSE:
       To compute the RA and Dec of the Sun at a given date.

 CALLING SEQUENCE:
       SUNPOS, jd, ra, dec, [elong, obliquity, /RADIAN ]
 INPUTS:
       jd    - The Julian date of the day (and time), scalar or vector
               usually double precision
 OUTPUTS:
       ra    - The right ascension of the sun at that date in DEGREES
               double precision, same number of elements as jd
       dec   - The declination of the sun at that date in DEGREES

 OPTIONAL OUTPUTS:
       elong - Ecliptic longitude of the sun at that date in DEGREES.
       obliquity - the obliquity of the ecliptic, in DEGREES

 OPTIONAL INPUT KEYWORD:
       /RADIAN - If this keyword is set and non-zero, then all output variables 
               are given in Radians rather than Degrees

 NOTES:
       Patrick Wallace (Rutherford Appleton Laboratory, UK) has tested the
       accuracy of a C adaptation of the sunpos.pro code and found the 
       following results.   From 1900-2100 SUNPOS  gave 7.3 arcsec maximum 
       error, 2.6 arcsec RMS.  Over the shorter interval 1950-2050 the figures
       were 6.4 arcsec max, 2.2 arcsec RMS.  

       The returned RA and Dec are in the given date's equinox.

       Procedure was extensively revised in May 1996, and the new calling
       sequence is incompatible with the old one.
 METHOD:
       Uses a truncated version of Newcomb's Sun.    Adapted from the IDL
       routine SUN_POS by CD Pike, which was adapted from a FORTRAN routine
       by B. Emerson (RGO).
 EXAMPLE:
       (1) Find the apparent RA and Dec of the Sun on May 1, 1982
       
       IDL> jdcnv, 1982, 5, 1,0 ,jd      ;Find Julian date jd = 2445090.5   
       IDL> sunpos, jd, ra, dec
       IDL> print,adstring(ra,dec,2)
                02 31 32.61  +14 54 34.9

       The Astronomical Almanac gives 02 31 32.58 +14 54 34.9 so the error
               in SUNPOS for this case is < 0.5".      

       (2) Find the apparent RA and Dec of the Sun for every day in 1997

       IDL> jdcnv, 1997,1,1,0, jd                ;Julian date on Jan 1, 1997
       IDL> sunpos, jd+ dindgen(365), ra, dec    ;RA and Dec for each day 

 MODIFICATION HISTORY:
       Written by Michael R. Greason, STX, 28 October 1988.
       Accept vector arguments, W. Landsman     April,1989
       Eliminated negative right ascensions.  MRG, Hughes STX, 6 May 1992.
       Rewritten using the 1993 Almanac.  Keywords added.  MRG, HSTX, 
               10 February 1994.
       Major rewrite, improved accuracy, always return values in degrees
       W. Landsman  May, 1996 
       Added /RADIAN keyword,    W. Landsman       August, 1997
       Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/sunpos.pro)

SUNSYMBOL

 NAME:
	SUNSYMBOL
 PURPOSE:
	Return the Sun symbol as a subscripted postscript character string
 EXPLANATION:
	Returns the Sun symbol (circle with a dot in the middle) as a 
	(subscripted) postscript character string.    Needed because although 
	the Sun symbol	is available using the vector fonts as the string 
	'!9n', it is not in the standard postscript set.   

 CALLING SEQUENCE:
	result = SUNSYMBOL([FONT= ])

 INPUTS:
	None

 OPTIONAL INPUT KEYWORDS:
       font = scalar font graphics keyword (-1,0 or 1) for text.   Note that
              this keyword is useful for printing text with XYOUTS but *not*
              e.g. the XTIT keyword to PLOT where the font call to PLOT takes
              precedence.

 OUTPUTS:
	result - a scalar string representing the Sun symbol.   A different
		string is output depending (1) the device is postscript and
		hardware fonts are used (!P.FONT=0), (2) vector fonts are used,
		or (3) hardware fonts are used on a non-postscript device.
		For case (3), SUNSYMBOL simply outputs the 3 character string
		'Sun'

 EXAMPLE:
	To make the X-axis of a plot read  M/M_Sun
	IDL>  plot,indgen(10),xtit = 'M / M' + sunsymbol()

 RESTRICTIONS:
	(1) The postscript output does not have the dot perfectly centered in 
		the circle.   For a better symbol, consider postprocessing with
               psfrag (see http://www.astrobetter.com/idl-psfrag/ ).
	(2) SUNSYMBOL() includes subscript output positioning commands in the 
		output string.
       (3) True type fonts (!p.font = 1) are not supported.   If you want
           to make a Sun symbol with true type fonts, see the discussion of
           installing the Marvosym font at http://tinyurl.com/mst5q 
 REVISION HISTORY:
	Written,  W. Landsman,    HSTX          April, 1997
	Converted to IDL V5.0   W. Landsman   September 1997
       Allow font keyword to be passed.  T. Robishaw Apr. 2006

(See $IDLUTILS_DIR/goddard/pro/plot/sunsymbol.pro)

SXADDHIST

 NAME:
	SXADDHIST                           
 PURPOSE:
	Procedure to add HISTORY (or COMMENT) line(s) to a FITS header

 EXPLANATION:
       The advantage of using SXADDHIST instead of SXADDPAR is that with 
       SXADDHIST many HISTORY or COMMENT records can be added in a single call.

 CALLING SEQUENCE
	sxaddhist, history, header, [ /PDU, /COMMENT ]

 INPUTS:
	history - string or string array containing history or comment line(s)
		to add to the FITS header
 INPUT/OUTPUT
	header - FITS header (string array).   Upon output, it will contain the
               specified HISTORY records added to the end

 OPTIONAL KEYWORD INPUTS:
       /BLANK - If specified then blank ('       ') keywords will be written
              rather than 'HISTORY ' keywords.
       /COMMENT - If specified, then 'COMMENT ' keyword will be written rather
              than 'HISTORY ' keywords.    
              Note that according to the FITS definition, any number of 
              'COMMENT' and 'HISTORY' or blank keywords may appear in a header,
              whereas all other keywords may appear only once.   
	LOCATION=key - If present, the history will be added before this
	       keyword.  Otherwise put it at the end.
	/PDU - if specified, the history will be added to the primary
		data unit header, (before the line beginning BEGIN EXTENSION...)               
		Otherwise, it will be added to the end of the header.
               This has meaning only for extension headers using the STScI
               inheritance convention. 
 OUTPUTS:
	header - updated FITS header

 EXAMPLES:
	sxaddhist, 'I DID THIS', header      ;Add one history record

	hist = strarr(3)
	hist[0] = 'history line number 1'
	hist[1[ = 'the next history line'
	hist[2] = 'the last history line'
	sxaddhist, hist, header              ;Add three history records

 SIDE EFFECTS:
       Header array is truncated to the final END statement
	LOCATION overrides PDU.
 HISTORY:
	D. Lindler  Feb. 87
	April 90  Converted to new idl  D. Lindler
	Put only a single space after HISTORY   W. Landsman  November 1992
	Aug. 95	  Added PDU keyword parameters
	Converted to IDL V5.0   W. Landsman   September 1997
	LOCATION added.  M. Greason, 28 September 2004.

(See $IDLUTILS_DIR/goddard/pro/fits/sxaddhist.pro)

SXADDPAR

 NAME:
       SXADDPAR
 PURPOSE:
       Add or modify a parameter in a FITS header array.

 CALLING SEQUENCE:
       SXADDPAR, Header, Name, Value, [ Comment,  Location, /SaveComment, 
                               BEFORE =, AFTER = , FORMAT= , /PDU]

 INPUTS:
       Header = String array containing FITS or STSDAS header.    The
               length of each element must be 80 characters.    If not 
               defined, then SXADDPAR will create an empty FITS header array.

       Name = Name of parameter. If Name is already in the header the value 
               and possibly comment fields are modified.  Otherwise a new 
               record is added to the header.  If name is equal to 'COMMENT'
               or 'HISTORY' or a blank string then the value will be added to 
               the record without replacement.  For these cases, the comment 
               parameter is ignored.

       Value = Value for parameter.  The value expression must be of the 
               correct type, e.g. integer, floating or string.  String values
                of 'T' or 'F' are considered logical values.

 OPTIONAL INPUT PARAMETERS:
       Comment = String field.  The '/' is added by this routine.  Added 
               starting in position 31.    If not supplied, or set equal to 
               '', or /SAVECOMMENT is set, then the previous comment field is 
               retained (when found) 

       Location = Keyword string name.  The parameter will be placed before the
               location of this keyword.    This parameter is identical to
               the BEFORE keyword and is kept only for consistency with
               earlier versions of SXADDPAR.

 OPTIONAL INPUT KEYWORD PARAMETERS:
       BEFORE  = Keyword string name.  The parameter will be placed before the
               location of this keyword.  For example, if BEFORE='HISTORY'
               then the parameter will be placed before the first history
               location.  This applies only when adding a new keyword;
               keywords already in the header are kept in the same position.

       AFTER   = Same as BEFORE, but the parameter will be placed after the
               location of this keyword.  This keyword takes precedence over
               BEFORE.

       FORMAT  = Specifies FORTRAN-like format for parameter, e.g. "F7.3".  A
               scalar string should be used.  For complex numbers the format
               should be defined so that it can be applied separately to the
               real and imaginary parts.  If not supplied then the default is
               'G19.12' for double precision, and 'G14.7' for floating point.

       /PDU    = specifies keyword is to be added to the primary data unit
               header. If it already exists, it's current value is updated in
               the current position and it is not moved.
       /SAVECOMMENT = if set, then any existing comment is retained, i.e. the
               COMMENT parameter only has effect if the keyword did not 
               previously exist in the header.
 OUTPUTS:
       Header = updated FITS header array.

 EXAMPLE:
       Add a keyword 'TELESCOP' with the value 'KPNO-4m' and comment 'Name
       of Telescope' to an existing FITS header h.

       IDL> sxaddpar, h, 'TELESCOPE','KPNO-4m','Name of Telescope'
 NOTES:
       The functions SXADDPAR() and FXADDPAR() are nearly identical, with the
       major difference being that FXADDPAR forces required FITS keywords
       BITPIX, NAXISi, EXTEND, PCOUNT, GCOUNT to appear in the required order
       in the header, and FXADDPAR supports the OGIP LongString convention.   
       There is no particular reason for having two nearly identical 
       procedures, but both are too widely used to drop either one.

       All HISTORY records are inserted in order at the end of the header.

       All COMMENT records are also inserted in order at the end of the header
       header, but before the HISTORY records.  The BEFORE and AFTER keywords
       can override this.

       All records with no keyword (blank) are inserted in order at the end of
       the header, but before the COMMENT and HISTORY records.  The BEFORE and
       AFTER keywords can override this.

 RESTRICTIONS:
       Warning -- Parameters and names are not checked
               against valid FITS parameter names, values and types.

 MODIFICATION HISTORY:
       DMS, RSI, July, 1983.
       D. Lindler Oct. 86  Added longer string value capability
       Converted to NEWIDL  D. Lindler April 90
       Added Format keyword, J. Isensee, July, 1990
       Added keywords BEFORE and AFTER. K. Venkatakrishna, May '92
       Pad string values to at least 8 characters   W. Landsman  April 94
       Aug 95: added /PDU option and changed routine to update last occurence
               of an existing keyword (the one SXPAR reads) instead of the
               first occurence.
       Comment for string data can start after column 32 W. Landsman June 97
       Make sure closing quote supplied with string value  W. Landsman  June 98
       Converted to IDL V5.0    W. Landsman   June 98
       Increase precision of default formatting of double precision floating
               point values.   C. Gehman, JPL  September 1998
       Mar 2000, D. Lindler, Modified to use capital E instead of lower case
               e for exponential formats.
       Apr 2000, Make user-supplied format upper-case  W. Landsman 
       Oct 2001, Treat COMMENT or blank string like HISTORY keyword W. Landsman
       Jan 2002, Allow BEFORE, AFTER to apply to COMMENT keywords W. Landsman
       June 2003, Added SAVECOMMENT keyword    W. Landsman
       Jan 2004, If END is missing, then add it at the end W. Landsman
       May 2005 Fix SAVECOMMENT error with non-string values W. Landsman
       Oct 2005 Jan 2004 change made SXADDPAR fail for empty strings W.L.
       May 2011 Fix problem with slashes in string values W.L.

(See $IDLUTILS_DIR/goddard/pro/fits/sxaddpar.pro)

SXDELPAR

 NAME:
	SXDELPAR
 PURPOSE:
	Procedure to delete a keyword parameter(s) from a FITS header

 CALLING SEQUENCE:
	sxdelpar, h, parname

 INPUTS:
	h - FITS or STSDAS header, string array
	parname - string or string array of keyword name(s) to delete

 OUTPUTS:
	h - updated FITS header, If all lines are deleted from 
		the header, then h is returned with a value of 0

 EXAMPLE:
	Delete the astrometry keywords CDn_n from a FITS header, h

	IDL> sxdelpar, h, ['CD1_1','CD1_2','CD2_1','CD2_2']

 NOTES:
	(1)  No message is returned if the keyword to be deleted is not found
	(2)  All appearances of a keyword in the header will be deleted
 HISTORY:
	version 1  D. Lindler Feb. 1987
	Test for case where all keywords are deleted    W. Landsman Aug 1995 
       Allow for headers with more than 32767 lines W. Landsman Jan. 2003
       Use ARRAY_EQUAL, cleaner syntax  W. L.  July 2009

(See $IDLUTILS_DIR/goddard/pro/fits/sxdelpar.pro)

SXGINFO

 NAME:
	SXGINFO

 PURPOSE:
	Return information on all group parameters in an STSDAS header.
 EXPLANATION:
	Return datatype, starting byte, and number bytes for all group
	parameters in an STSDAS file.     Obtaining these values 
	greatly speed up execution time in subsequent calls to SXGPAR.

 CALLING SEQUENCE:
	sxginfo, h, par, type, sbyte, nbytes

 INPUTS:
	h - header returned by SXOPEN
	par - parameter block returned by SXREAD or multiple
		parameter blocks stored in array of dimension
		greater than one.

 OUTPUT:
	type - data type (if not supplied or null string, the
		header is searched for type,sbyte, and nbytes)
	sbyte - starting byte in parameter block for data
	nbytes - number of bytes in parameter block for data

	The number of elements in type,sbyte and nbytes equals the total
	number of group parameters.

 METHOD:
	The parameter type for each parameter is obtained
	from PDTYPEn keyword.  If not found then DATATYPE keyword
	value is used.  If that is not found then BITPIX is
	used.  BITPIX=8, byte; BITPIX=16 integer*2; BITPIX=32
	integer*4.

 NOTES:
	For an example of the use of SXGINFO, see CONV_STSDAS

 HISTORY:
	version 1  W. Landsman   Apr. 93

	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/sxginfo.pro)

SXGPAR

 NAME:
	SXGPAR                           

 PURPOSE:
	Obtain group parameter value in SDAS/FITS file

 CALLING SEQUENCE:
	result = sxgpar( h, par, name, [ type, sbyte, nbytes] )

 INPUTS:
	h - header returned by SXOPEN
	par - parameter block returned by SXREAD or multiple
		parameter blocks stored in array of dimension
		greater than one.
	name - parameter name (keyword PTYPEn) or integer
		parameter number.

 OPTIONAL INPUT/OUTPUT
	type - data type (if not supplied or null string, the
		header is searched for type,sbyte, and nbytes)
	sbyte - starting byte in parameter block for data
	nbytes - number of bytes in parameter block for data

 OUTPUT:
	parameter value or value(s) returned as function value

 SIDE EFFECTS:
	If an error occured then !err is set to -1

 OPERATIONAL NOTES:
	Supplying type, sbyte and nbytes greatly decreases execution
	time.  The best way to get the types is on the first call
	pass undefined variables for the three parameters or set
	type = ''.  The routine will then return their values for
	use in subsequent calls.
	
 METHOD:
	The parameter type for parameter n is obtained
	from PDTYPEn keyword.  If not found then DATATYPE keyword
	value is used.  If that is not found then BITPIX is
	used.  BITPIX=8, byte; BITPIX=16 integer*2; BITPIX=32
	integer*4.

 HISTORY:
	version 1  D. Lindler  Oct. 86
	version 2  D. Lindler Jan. 90  added ability to process
		multiple parameter blocks in single call
	version 3  D. Lindler  (converted to New vaxidl)
       Apr 14 1991      JKF/ACC - fixed make_array datatypes(float/double)
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/sxgpar.pro)

SXGREAD

 NAME:
	SXGREAD
 PURPOSE:
	Read group parameters from a Space Telescope STSDAS image file     

 CALLING SEQUENCE:
	grouppar = sxgread( unit, group )

 INPUTS:
	UNIT   = Supply same unit as used in SXOPEN.
	GROUP  =  group number to read.  if omitted, read first group.
		The first group is number 0.

 OUTPUTS:
	GROUPPAR  =  parameter values from fits group parameter block.
		It is a byte array which may contain multiple data types.
		The function SXGPAR can be used to retrieve values from it.

 COMMON BLOCKS:
	Uses IDL Common STCOMMN to access parameters.
 SIDE EFFECTS:
	IO is performed. 
 MODIFICATION HISTORY:
	WRITTEN, Don Lindler, July, 1 1987
	MODIFIED, Don Neill, Jan 11, 1991 - derived from sxread.pro
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/sxgread.pro)

SXHCOPY

 NAME:
	SXHCOPY                            
 PURPOSE:
	Copies selected portions of one header to another

 CALLING SEQUENCE:
	sxhcopy, h, keyword1, keyword2, hout

 INPUTS:
	h - input header
	keyword1 - first keyword to copy
	keyword2 - last keyword to copy

 INPUT/OUTPUT:
	hout - header to copy the information to.

 METHOD:
	the headers lines from keyword1 to keyword2 are copied to
	the end of the output header.  No check is made to verify
	that a keyword value already exists in the output header.

 HISTORY:
	version 1  D. Lindler    Sept. 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/sxhcopy.pro)

SXHMAKE

 NAME:
       SXHMAKE
 PURPOSE:
       Create a basic STSDAS header file from an IDL data array

 CALLING SEQUENCE:
       sxhmake, Data, Groups, Header

 INPUTS:
       Data = IDL data array of the same type, dimensions and
               size as are to be written to file.
       Groups = # of groups to be written.

 OUTPUTS:
       Header = String array containing ST header file.

 PROCEDURE:
       Call sxhmake to create a header file.  Then call sxopen to
       open output image, followed by sxwrite to write the data.
       If you do not plan to change the header created by sxhmake
       before calling sxopen, you might consider using sxmake which
       does both steps.

 MODIFICATION HISTORY:
       Don Lindler  Feb 1990 modified from SXMAKE by DMS, July, 1983.
       D. Lindler April 90  Converted to new VMS IDL
       M. Greason May 1990  Header creation bugs eliminated.
       W. Landsman Aug 1997 Use SYSTIME() instead of !STIME for V5.0 
       Converted to IDL V5.0   W. Landsman   September 1997
       Recognize unsigned datatype    January 2000   W. Landsman

(See $IDLUTILS_DIR/goddard/pro/sdas/sxhmake.pro)

SXHREAD

 NAME:
       SXHREAD
 PURPOSE:
       Procedure to read a STSDAS header from disk.
 EXPLANATION:
       This version of SXHREAD can read two types of disk files
       (1)  Unix stream files with a CR after every 80 bytes
       (2)  Variable length record files 
       (3)  Fixed length (80 byte) record files

 CALLING SEQUENCE:
       sxhread, name, header

 INPUT:
       name - file name, scalar string.  An extension of .hhh is appended
               if not already supplied.   (Note STSDAS headers are required
               to have a 3 letter extension ending in 'h'.)   gzip extensions
               .gz will be recognized as compressed.
 OUTPUT:
       header - STSDAS header, string array
 NOTES:
       SXHREAD  does not do any checking to see if the file is a valid
       STSDAS header.    It simply reads the file into a string array with
       80 byte elements

 HISTORY:
       Version 1  D. Lindler  July, 1987
       Version 2  M. Greason, August 1990
       Use READU for certain ST VAX GEIS files   W. Landsman January, 1992
       Read variable length Unix files  E. Deutsch/W. Landsman November, 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Updated by E. Artigau to handle gzipped fits  August 2004
       Remove VMS support, W. Lnadsman September 2006

(See $IDLUTILS_DIR/goddard/pro/sdas/sxhread.pro)

SXHWRITE

 NAME:
       SXHWRITE
 PURPOSE:
       Procedure to write an STSDAS or FITS header to disk as a *.hhh file.

 CALLING SEQUENCE:
       SXHWRITE,name,h

 INPUTS:
       name - file name. If an extension is supplied it must be 3 characters
               ending in "h".
       h - FITS header, string array

 SIDE EFFECTS:
       File with specified name is written.  If qualifier not specified
       then .hhh is used
   
       SXHWRITE will modify the header in the following ways, if necessary
       (1)  If not already present, an END statement is added as the 
               last line.   Lines after an existing END statment are
               deleted.
       (2)  Spaces are appended to force each line to be 80 characters.
       (3)  On Unix machines, a carriage return is appended at the end
               of each line.   This is consistent with STSDAS and allows
               the file to be directly displayed on a stream device

 PROCEDURES USED:
       zparcheck, fdecomp
 HISTORY:
       version 1  D. Lindler  June 1987
       conversion cleaned up.  M. Greason, June 1990
       Add carriage return at the end of Unix files   W. Landsman Oct 1991
       Use SYSTIME() instead of !STIME for V5.0 compatibility Aug 1997
       Assume since V55, remove VMS support

(See $IDLUTILS_DIR/goddard/pro/sdas/sxhwrite.pro)

SXMAKE

 NAME:
       SXMAKE
 PURPOSE:
       Create a basic ST header file from an IDL array prior to writing data.

 CALLING SEQUENCE:
       sxmake, Unit, File, Data, Par, Groups, Header, [ PSIZE = ]

 INPUTS:
       Unit = Logical unit number from 1 to 9.
       File = file name of data and header files to create.   If no file name
              extension is supplied then the default is to use .hhh for the
              header file extension and .hhd for the data file extension    
              If an extension is supplied, it should be of the form .xxh
              where xx are any alphanumeric characters.
       Data = IDL data array of the same type, dimensions and
               size as are to be written to file.
       Par = # of elements in each parameter block for each data record.  If 
             set equal to 0, then parameter blocks will not be written.  The 
             data type of the parameter blocks must be the same as the data 
             array.   To get around this restriction, use the PSIZE keyword.
       Groups = # of groups to write.  If 0 then write in basic
               format without groups.  

 OPTIONAL INPUT PARAMETERS:
       Header = String array containing ST header file.  If this
               parameter is omitted, a basic header is constructed.
               If included, the basic parameters are added to the
               header using sxaddpar.  The END keyword must terminate
               the parameters in Header.

 OPTIONAL KEYWORD INPUT PARAMETER:
        PSIZE - Integer scalar giving the number of bits in the parameter 
               block.    If the PSIZE keyword is given, then the Par input
               parameter is ignored.
                
 OPTIONAL OUTPUT PARAMETERS:
       Header = ST header array, an 80 by N character array.

 COMMON BLOCKS:
       Stcommn - as used in sxwrite, sxopen, etc.

 SIDE EFFECTS:
       The header file is created and written and then the
       data file is opened on the designated unit.

 RESTRICTIONS:
       Header files must be named .xxh and data files must be
       named .xxd, where xx are any alphanumeric characters.

 PROCEDURE:
       Call sxmake to create a header file.  Then call sxwrite
       to output each group.
 
 PROCEDURES USED:
       GET_DATE, SXADDPAR, SXOPEN
 MODIFICATION HISTORY:
       DMS, July, 1983.
       converted to new VMS IDL  April 90
       Use SYSTIME() instead of !STIME   W. Landsman   Aug 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Added optional PSIZE keyword   August 1999 W. Landsman 
       Recognize unsigned datatype    January 2000   W. Landsman

(See $IDLUTILS_DIR/goddard/pro/sdas/sxmake.pro)

SXOPEN

 NAME:
       SXOPEN
 PURPOSE:
       Open a Space Telescope formatted (STSDAS) header file.
 EXPLANATION:
       Saves the parameters required subsequent SX routines in
       the common block Stcommn.  Optionally save the header in 
       the string array Header, and the history in the string array
       History.  Open the data file associated with this
       header on the same unit.

 CALLING SEQUENCE:
       SXOPEN, Unit, Fname [, Header [,History] [,Access]]

 INPUTS:
       Unit = IDL unit used for IO.  Must be from 1 to 9.
       Fname = File name of header file.  Default extension
               is .hhh for header files and .hhd for data
               files.    If an extension is supplied it must have the 
               form .xxh where xx are any alphanumeric characters. The
               data file must have extension .xxd
               No version number is allowed.  Most recent versions
               of the files are used.

 OPTIONAL INPUT PARAMETER:
       Access = 'R' to open for read, 'W' to open for write.

 OUTPUTS:
       Stcommn = Common block containing ST parameter blocks.
               (Long arrays.)

 OPTIONAL OUTPUT PARAMETERS:
       Header = 80 char by N string array containing the
               names, values and comments from the FITS header.
               Use the function SXPAR to obtain individual
               parameter values.
       History = String array containing the value of the
               history parameter.

 COMMON BLOCKS:
       STCOMMN - Contains RESULT(20,10) where RESULT(i,LUN) =
       0 - 121147 for consistency check, 1 - Unit for consistency,
       2 - bitpix, 3 - naxis, 4 - groups (0 or 1), 5 - pcount,
       6 - gcount, 7 - psize, 8 - data type as idl type code,
       9 - bytes / record, 10 to 10+N-1 - dimension N,
       17 = record length of file in bytes.
       18 - # of groups written, 19 = gcount.

 SIDE EFFECTS:
       The data and header files are accessed.

 RESTRICTIONS:
       Works only for disc files.  The data file must have
       must have the extension ".xxd" and the header file must
       have the extension ".xxh" where x is any alphanumeric character

 PROCEDURE:
       The header file is opened and each line is read.
       Important parameters are stored in the output
       parameter.  If the last two parameters are specified
       the parameter names and values are stored.  The common
       block STCOMMN is filled with the type of data, dimensions,
       etc. for use by SXREAD.

       If access is for write, each element of the header
       array, which must be supplied, is written to the
       header file.  The common block is filled with
       relevant parameters for SXWRITE.  A keyword of "END"
       ends the header.

 MODIFICATION HISTORY:
       Written, DMS, May, 1983.
       D. Lindler Feb. 1990
               Modified to allow var. record length header files.
       D. Lindler April 1990   Conversion to new VMS IDL
       Added /BLOCK when opening new .hhd file
       Converted to IDL V5.0   W. Landsman   September 1997
       Recognize unsigned datatype for V5.1 or greater   W. Landsman Jan 2000
       Assume since V5.5  W. Landsman Sep 2006

(See $IDLUTILS_DIR/goddard/pro/sdas/sxopen.pro)

SXPAR

 NAME:
      SXPAR
 PURPOSE:
      Obtain the value of a parameter in a FITS header

 CALLING SEQUENCE:
      result = SXPAR( Hdr, Name, [ Abort, COUNT=, COMMENT =, /NoCONTINUE, 
                                           /SILENT  ])   

 INPUTS:
      Hdr =  FITS header array, (e.g. as returned by READFITS) 
             string array, each element should have a length of 80 characters      

      Name = String name of the parameter to return.   If Name is of the
             form 'keyword*' then an array is returned containing values of
             keywordN where N is a positive (non-zero) integer.  The value of 
             keywordN will be placed in RESULT[N-1].  The data type of RESULT 
             will be the type of the first valid match of keywordN found.

 OPTIONAL INPUTS:
       ABORT - string specifying that SXPAR should do a RETALL
               if a parameter is not found.  ABORT should contain
               a string to be printed if the keyword parameter is not found.
               If not supplied, SXPAR will return quietly with COUNT = 0
               (and !ERR = -1) if a keyword is not found.

 OPTIONAL INPUT KEYWORDS: 
       /NOCONTINUE = If set, then continuation lines will not be read, even
                 if present in the header
       /SILENT - Set this keyword to suppress warning messages about duplicate
                 keywords in the FITS header.

 OPTIONAL OUTPUT KEYWORDS:
       COUNT - Optional keyword to return a value equal to the number of 
               parameters found by SXPAR, integer scalar

       COMMENT - Array of comments associated with the returned values

 OUTPUTS:
       Function value = value of parameter in header.
               If parameter is double precision, floating, long or string,
               the result is of that type.  Apostrophes are stripped
               from strings.  If the parameter is logical, 1b is
               returned for T, and 0b is returned for F.
               If Name was of form 'keyword*' then a vector of values
               are returned.

 SIDE EFFECTS:
       !ERR is set to -1 if parameter not found, 0 for a scalar
       value returned.  If a vector is returned it is set to the
       number of keyword matches found.    The use of !ERR is deprecated, and
       instead the COUNT keyword is preferred

       If a keyword (except HISTORY or COMMENT) occurs more than once in a 
       header, a warning is given, and the *last* occurence is used.

 EXAMPLES:
       Given a FITS header, h, return the values of all the NAXISi values
       into a vector.    Then place the history records into a string vector.

       IDL> naxisi = sxpar( h ,'NAXIS*')         ; Extract NAXISi value
       IDL> history = sxpar( h, 'HISTORY' )      ; Extract HISTORY records

 PROCEDURE:
       The first 8 chacters of each element of Hdr are searched for a 
       match to Name.  The value from the last 20 characters is returned.  
       An error occurs if there is no parameter with the given name.

       If a numeric value has no decimal point it is returned as type
       LONG.   If it contains more than 8 numerals, or contains the 
       characters 'D' or 'E', then it is returned as type DOUBLE.  Otherwise
       it is returned as type FLOAT.    Very large integer values, outside
       the range of valid LONG, are returned as DOUBLE.

       If the value is too long for one line, it may be continued on to the
       the next input card, using the OGIP CONTINUE convention.  For more info,
       see http://fits.gsfc.nasa.gov/registry/continue_keyword.html

       Complex numbers are recognized as two numbers separated by one or more
       space characters.

       If a numeric value has no decimal point (or E or D) it is returned as
       type LONG.  If it contains more than 8 numerals, or contains the
       character 'D', then it is returned as type DOUBLE.  Otherwise it is
       returned as type FLOAT.    If an integer is too large to be stored as
       type LONG, then it is returned as DOUBLE.

 NOTES:
       The functions SXPAR() and FXPAR() are nearly identical, although
       FXPAR() has slightly more sophisticated parsing, and additional keywords
       to specify positions in the header to search (for speed), and to force
       the output to a specified data type..   There is no
       particular reason for having two nearly identical procedures, but
       both are too widely used to drop either one.

 PROCEDURES CALLED:
       GETTOK(), VALID_NUM()
 MODIFICATION HISTORY:
       DMS, May, 1983, STPAR Written.
       D. Lindler Jan 90 added ABORT input parameter
       J. Isensee Jul,90 added COUNT keyword
       W. Thompson, Feb. 1992, added support for FITS complex values.
       W. Thompson, May 1992, corrected problem with HISTORY/COMMENT/blank
               keywords, and complex value error correction.
       W. Landsman, November 1994, fix case where NAME is an empty string 
       W. Landsman, March 1995,  Added COMMENT keyword, ability to read
               values longer than 20 character
       W. Landsman, July 1995, Removed /NOZERO from MAKE_ARRAY call
       T. Beck May 1998, Return logical as type BYTE
       W. Landsman May 1998, Make sure integer values are within range of LONG
       W. Landsman Feb 1998, Recognize CONTINUE convention 
       W. Landsman Oct 1999, Recognize numbers such as 1E-10 as floating point
       W. Landsman Jan 2000, Only accept integer N values when name = keywordN
       W. Landsman Dec 2001, Optional /SILENT keyword to suppress warnings
       W. Landsman/D. Finkbeiner  Mar 2002  Make sure extracted vectors 
             of mixed data type are returned with the highest type.
       W.Landsman Aug 2008  Use vector form of VALID_NUM()
       W. Landsman Jul 2009  Eliminate internal recursive call
       W. Landsman Apr 2012  Require vector numbers be greater than 0

(See $IDLUTILS_DIR/goddard/pro/fits/sxpar.pro)

SXREAD

 NAME:
	SXREAD
 PURPOSE:
	Read a Space Telescope STSDAS image file     

 CALLING SEQUENCE:
	result = sxread( Unit, group , [par] )

 INPUTS:
	UNIT  =  Unit number of file, must be from 1 to 9.
		Unit must have been opened with SXOPEN.
	GROUP  =  group number to read.  if omitted, read first record.
		The first record is number 0.
 OUTPUTS:
	Result of function  =  array constructed from designated record.

 OPTIONAL OUTPUT:
	PAR  =  Variable name into which parameter values from STSDAS
		group parameter block are read.  It is a byte array
		which may contain multiple data types.  The function
		SXGPAR can be used to retrieve values from it.

 COMMON BLOCKS:
	Uses IDL Common STCOMMN to access parameters.

 NOTES:
	Use the function SXGREAD to read the group parameter blocks without
	having to read the group array.

	If the STSDAS file does not contain groups, then the optional output
	parameter PAR is returned undefined, but no error message is given.

 SIDE EFFECTS:
	IO is performed. 
 MODIFICATION HISTORY:
	WRITTEN, Don Lindler, July, 1 1987
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/sxread.pro)

SXWRITE

 NAME:
	SXWRITE
 PURPOSE:
	Write a group of data and parameters in ST format
	to a STSDAS data file.

 CALLING SEQUENCE:
	SXWRITE, Unit, Data,[ Par]

 INPUTS:
	Unit = unit number of file.  The file must have been
		previously opened by SXOPEN.
	Data = Array of data to be written.  The dimensions
		must agree with those supplied to SXOPEN and written
		into the FITS header.  The type is converted if
		necessary.

 OPTIONAL INPUT PARAMETERS:
	Par = parameter block.  The size of this array must
		agree with the Psize parameter in the FITS header.

 OUTPUTS:
	None.
 COMMON BLOCKS:
	STCOMMN - Contains RESULT(20,10) where RESULT(i,LUN) =
	0 - 121147 for consistency check, 1 - Unit for consistency,
	2 - bitpix, 3 - naxis, 4 - groups (0 or 1), 5 - pcount,
	6 - gcount, 7 - psize, 8 - data type as idl type code,
	9 - bytes / record, 10 to 10+N-1 - dimension N,
	18 - # of groups written, 19 = gcount.

 SIDE EFFECTS:
	The data are written into the next group.

 RESTRICTIONS:
	SXOPEN must have been called to initialize the
	header and the common block.

 MODIFICATION HISTORY:
	DMS, July, 1983.
	D.Lindler July, 1986 - changed block size of file to 512
			moved group parameters after the groups data.
	D.Lindler July, 1987 - modified to allow any size parameter block
			(in bytes).
	D. Lindler  April, 1990 - converted to new VMS IDL
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas/sxwrite.pro)

SYMCAT

 NAME:
       SYMCAT

 PURPOSE:

       This function provides a symbol catalog for specifying a number of plotting symbols.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Graphics

 CALLING SEQUENCE:

       Plot, findgen(11), PSYM=SYMCAT(theSymbol)

       To connect symbols with lines, use a negative value for the PSYM keyword:

       Plot, findgen(11), PSYM=-SYMCAT(theSymbol)

 INPUTS:

       theSymbol:    The number of the symbol you wish to use. Possible values are:

       0  : No symbol.
       1  : Plus sign.
       2  : Asterisk.
       3  : Dot (period).
       4  : Open diamond.
       5  : Open upward triangle.
       6  : Open square.
       7  : X.
       8  : Defined by the user with USERSYM.
       9  : Open circle.
      10  : Histogram style plot.
      11  : Open downward triangle.
      12  : Open rightfacing triangle.
      13  : Open leftfacing triangle.
      14  : Filled diamond.
      15  : Filled square.
      16  : Filled circle.
      17  : Filled upward triangle.
      18  : Filled downward triangle.
      19  : Filled rightfacing triangle.
      20  : Filled leftfacing triangle.
      21  : Hourglass.
      22  : Filled Hourglass.
      23  : Bowtie.
      24  : Filled bowtie.
      25  : Standing Bar.
      26  : Filled Standing Bar.
      27  : Laying Bar.
      28  : Filled Laying Bar.
      29  : Hat up.
      30  : Hat down.
      31  : Hat right.
      32  : Hat down.
      33  : Big cross.
      34  : Filled big cross.
      35  : Circle with plus.
      36  : Circle with X.
      37  : Upper half circle.
      38  : Filled upper half circle.
      39  : Lower half circle.
      40  : Filled lower half circle.
      41  : Left half circle.
      42  : Filled left half circle.
      43  : Right half circle.
      44  : Filled right half circle.
      45  : Star.
      46  : Filled star.

 RETURN VALUE:

       The return value is whatever is appropriate for passing along
       to the PSYM keyword of (for example) a PLOT or OPLOT command.
       For the vast majority of the symbols, the return value is 8.

 KEYWORDS:
 
       COLOR:  Set this keyword to the color (index or 24-bit value) of
               the color desired. For example:
               
               Plot, Findgen(11), COLOR=cgColor('yellow'), PSYM=-SYMCAT(4, COLOR=cgColor('green'))

       THICK:  Set this keyword to the thickness desired. Default is 1. 

 MODIFICATION HISTORY:

       Written by David W. Fanning, 2 September 2006. Loosely based on the
          program MC_SYMBOL introduced on the IDL newsgroup 1 September 2006,
          and MPI_PLOTCONFIG__DEFINE from the Coyote Library.
       2 October 2006. DWF. Modified to allow PSYM=8 and PSYM=10 to have
          their normal meanings. This shifted previous symbols by two values
          from their old meanings. For example, an hourglass went from symbol
          number 19 to 21.
       Whoops! Added two symbols but forgot to change limits to allow for them. 4 May 2007. DWF.
       Added THICK keyword. 21 Aug 2007. DWF.
       Added COLOR keyword and made THICK keyword apply to all symbols. 11 Nov 2008. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/symcat.pro)

TABINV

 NAME:
       TABINV     
 PURPOSE:  
       To find the effective index of a function value in an ordered vector.
       
 CALLING SEQUENCE:
       TABINV, XARR, X, IEFF, [/FAST]
 INPUTS:
       XARR - the vector array to be searched, must be monotonic
               increasing or decreasing
       X    - the function value(s) whose effective
               index is sought (scalar or vector)

 OUTPUT:
       IEFF - the effective index or indices of X in XARR
              always floating point, same # of elements as X

 OPTIONAL KEYWORD INPUT:
       /FAST - If this keyword is set, then the input vector is not checked
               for monotonicity, in order to improve the program speed.
 RESTRICTIONS:
       TABINV will abort if XARR is not monotonic.  (Equality of 
       neighboring values in XARR is allowed but results may not be
       unique.)  This requirement may mean that input vectors with padded
       zeroes could cause routine to abort.

 PROCEDURE:
       VALUE_LOCATE() is used to find the values XARR[I]
       and XARR[I+1] where XARR[I] < X < XARR[I+1].
       IEFF is then computed using linear interpolation 
       between I and I+1.
               IEFF = I + (X-XARR[I]) / (XARR[I+1]-XARR[I])
       Let N = number of elements in XARR
               if x < XARR[0] then IEFF is set to 0
               if x > XARR[N-1] then IEFF is set to N-1

 EXAMPLE:
       Set all flux values of a spectrum (WAVE vs FLUX) to zero
       for wavelengths less than 1150 Angstroms.
         
       IDL> tabinv, wave, 1150.0, I
       IDL> flux[ 0:fix(I) ] = 0.                         

 FUNCTIONS CALLED:
       None
 REVISION HISTORY:
       Adapted from the IUE RDAF                     January, 1988         
       More elegant code  W. Landsman                August, 1989
       Mod to work on 2 element decreasing vector    August, 1992
       Updated for V5.3 to use VALUE_LOCATE()     W. Landsman January 2000
       Work when both X and Xarr are integers     W. Landsman August 2001
       Use ARRAY_EQUAL, always internal double precision W.L.  July 2009
       Allow Double precision output, faster test for monotonicity.
                    WL, January 2012

(See $IDLUTILS_DIR/goddard/pro/math/tabinv.pro)

TABLE_APPEND

 NAME:
	TABLE_APPEND
 PURPOSE:
	Routine to append STSDAS tables to create a single table. 
	Input tables must all have identical columns.

 CALLING SEQUENCE:
	table_append,list,name

 INPUTS:
	list - string array listing the file names or a string
		scalar giving a file name template.
	name - output file name.
 SIDE EFFECTS:
	a new STSDAS table is created with the specified name.

 OPERATIONAL NOTES:
	all input tables must have the same number of columns
	with the same names, datatypes, and column order.
	Header parameters are taken only from the first table.

 HISTORY:
	version 1  D. Lindler	April 1989
       Removed call to non-standard system variable !DUMP WBL  September 1997
	Converted to IDL V5.0   W. Landsman   September 1997
       Use file_search rather than findfile  W. Landsman Sep 2006

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_append.pro)

TABLE_CALC

 NAME:
	TABLE_CALC 
 PURPOSE:
	Adds a new table column from a expression using existing columns

 CALLING SEQUENCE:
	table_calc, table, expression, table_out

 INPUTS:
	table - input SDAS table table
	expression - expression for new or updated column values.
		Any legal IDL expression is valid where existing
		column names can be used as variables.  User functions
		within the expression are allowed if the function
		is in an IDL library or previously compiled.

 OPTIONAL INPUT:
	table_out - output table name.  If not supplied, the
		input name is used.

 OUTPUTS:
	a new SDAS table file is created.

 EXAMPLES:

	 create a column WAVELENGTH in table TAB which is the average
	of the WLOW and WHIGH columns of table TAB.

		table_calc,'tab','WAVELENGTH=(WLOW+WHIGH)/2.0'

	add a column SINX which is the sin of column X to table JUNK.

		table_calc,'junk','SINX=sin(X)'

	add 10.0 to an existing column in table MYTAB.

		table_calc,'mytab','flux=flux+10.0'

 HISTORY
	version 1  D. Lindler November, 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_calc.pro)

TABLE_DELETE

 NAME:
	TABLE_DELETE 
 PURPOSE:
	Delete specified rows from an STSDAS table

 CALLING SEQUENCE:
	table_delete, name, rows, [ outname ]

 INPUT:
	name - table name
	rows - row (scalar) or rows(vector) to delete from the table

 OPTIONAL OUTPUT:
	outname - output table name, if not supplied the input name
		is used

 HISTORY:
	version 1  D. Lindler  April 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_delete.pro)

TABLE_EXT

 NAME:
	TABLE_EXT
 PURPOSE:
	Routine to extract columns from an STSDAS table

 CALLING SEQUENCE:
	TABLE_EXT, name, columns, v1, [v2,v3,v4,v5,v6,v7,v8,v9]
 INPUTS:
	name - table name, scalar string
	columns - table columns to extract.  Can be either 
		(1) String with names separated by commas
		(2) Scalar or vector of column numbers

 OUTPUTS:
	v1,...,v9 - values for the columns

 EXAMPLES:
	Read wavelength and throughput vectors from STSDAS table, wfpc_f725.tab

	IDL> table_ext,'wfpc_f725.tab','wavelength,throughput',w,t
		or
	IDL> table_ext,'wfpc_f725.tab',[1,2],w,t
	
 PROCEDURES CALLED:
	GETTOK(), TAB_READ, TAB_VAL()
 HISTORY:
	version 1  D. Lindler  May 1989
	Accept Column Numbers as well as names, W. Landsman  February 1996
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_ext.pro)

TABLE_HELP

 NAME:
	TABLE_HELP
 PURPOSE:
	Procedure to decribe an SDAS table file.

 CALLING SEQUENCE:
	table_help, tcb, header
	table_help, name

 INPUTS:
	tcb - table control block returned by TAB_READ or TAB_CREATE
	name -	the table name

 OPTIONAL INPUTS:
	header - header array returned by TAB_READ.  If supplied
		it will be printed, otherwise it won't.

 SIDE EFFECTS:
	text output as specified by !textout

 HISTORY:
	version 1  D. Lindler  JAN 1988
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_help.pro)

TABLE_LIST

 NAME:
	TABLE_LIST  
 PURPOSE:
	List the contents of an STSDAS table.
 EXPLANATION:
	Procedure to list contents of an STSDAS table.  This does not
	print the table in tabular form but instead for each row
	prints the column name followed by its value (one column per
	output line.

 CALLING SEQUENCE:
	table_list, name, row1, row2, [ TEXTOUT=, /HEADER ]

 INPUTS:
	name - table name

 OPTIONAL KEYWORD INPUT:
	TEXTOUT  - Scalar string giving output file name, or integer (1-5)
		specifying output device.   See TEXTOPEN for more info.
		Default is to display output at the terminal
	HEADER - if set, the header is printed before the selected row printout

 OPTIONAL INPUTS:
	row1 - first row to list (default = first row)
	row2 - last row to list (default = last row)

 OUTPUT:
	text output is written to the output device specified by the TEXTOUT
	keyword, or the nonstandard system variable !TEXTOUT

 PROCEDURES USED:
	TAB_COL, TAB_READ, TAB_SIZE, TAB_VAL(), TEXTOPEN, TEXTCLOSE

 HISTORY:
	version 1  D. Lindler   May 1989
	July 1996, DJL, added /header keyword to optionally print header
	August 1996, WBL, added TEXTOUT keyword
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_list.pro)

TABLE_PRINT

 NAME:
	TABLE_PRINT
 PURPOSE:
	Routine to print an stsdas table.

 CALLING SEQUENCE:
	table_print, name, columns, row1, row2

 INPUTS:
	name - table name
 
 OPTIONAL INPUTS:
	columns - vector of column numbers to be printed or a string
		with column names separated by commas. If not supplied
		or set to the null string, all columns are printed.

	row1 - first row to print.  (default=0)
	row2 - last row to print.  (default=last row in table)

 SIDE EFFECTS:
	text is printed as directed by !textout

 HISTORY:
	version 1, D. Lindler  Apr 89
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_print.pro)

TABLE_SORT

 NAME:
	TABLE_SORT
 PURPOSE:
	Procedure to sort an STSDAS table by the specified column

 CALLING SEQUENCE:
	table_sort, name, column, [ name_out ]

 INPUTS:
	name - table name
	column - column to sort on

 OPTIONAL INPUTS:
	name_out - output table name.  If not supplied, input name
		is used.

 HISTORY:
	version 1  D. Lindler  MAY 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/table_sort.pro)

TAB_ADDCOL

 NAME:
	TAB_ADDCOL   
 PURPOSE:
	Procedure to add a new column to an existing STSDAS table.

 CALLING SEQUENCE:
	tab_addcol, name, data, tcb, tab

 INPUTS:
	name - column name
	data - sample data of type to be written to the column.
		This parameter is only used to determine data type.

 INPUT/OUTPUTS:
	tcb - table control block
	tab - table array

 HISTORY:
	version 1  D. Lindler April 89
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_addcol.pro)

TAB_COL

 NAME:
	TAB_COL  
 PURPOSE:
	Procedure to extract column information from table control block

 CALLING SEQUENCE:
	tab_col, tcb, column, offset, width, datatype, name, units, format

 INPUTS:
	tcb - table control block returned by tab_open.
	column - column name (string) or column number

 OUTPUTS:
	offset - column offset bytes
	width - column width in bytes
	datatype - column data type:
		6 - real*4
		7 - real*8
		4 - integer*4
		1 - boolean
		2 - character string
	name - column name
	units - column units
	format - format code

 SIDE EFFECTS:
	If the column is not found then !err is set to -1.
	Otherwise !err is set to the column number (starting at one).

 HISTORY:
	version 1  D. Lindler  Jan 88
	Converted to NEW IDL  April 90
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_col.pro)

TAB_CREATE

 NAME:
	TAB_CREATE  
 PURPOSE:
	Procedure to create a new table file.

 CALLING SEQUENCE:
	tab_create, tcb, tab, maxcol, maxrows, row_len, tb_type

 OUTPUTS:
	tcb - table control block for reading from and writing
		to the file (see tab_open for description)
	tab - table array

 OPTIONAL INPUTS:
	maxcol - maximum allocated number of columns [default=10]
	maxrows - maximum allocated number of rows   [default=100]
	row_len - row length in 2 byte units	     [default=2*maxcol]
	tb_type - table type 'row' or 'column' ordered

 SIDE EFFECTS:
	Table file is created and left opened to unit number tcb(0,0)
	for writing.

 HISTORY:
	version 1   D. Lindler   Dec. 88
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_create.pro)

TAB_DEL

 NAME:
	TAB_DEL 
 PURPOSE:
	Delete specified row(s) from an STSDAS table

 CALLING SEQUENCE:
	tab_del, tcb, tab, rows

 INPUT/OUTPUTS
	tcb - table control block
	tab - table array

 OPTIONAL INPUTS:
	rows - row (scalar) or rows(vector) to delete from the table
		If not supplied all rows are deleted.

 HISTORY:
	version 1  D. Lindler  April 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_del.pro)

TAB_EXPAND

 NAME:
	TAB_EXPAND
 PURPOSE:
	routine to expand the size of an SDAS table file.

 CALLING SEQUENCE:
	tab_expand, tcb, tab, maxcol, maxrow, rowlen

 INPUT/OUTPUT:
	tcb - table control block returned by routine TAB_READ
		or TAB_CREATE.
	tab - table array

 OPTIONAL INPUTS:
	maxcol - new maximum number of columns.
	maxrow - new maximum number of rows.
	rowlen - new maximum row length in 2 byte units.

	If maxcol, maxrow, or rowlen are supplied with
	values less than the previous maximums, the previous
	maximums are used.  All values are defaulted to zero
	if not supplied.

 HISTORY:
	Version 1   D. Lindler   Dec. 88
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_expand.pro)

TAB_FORTOSPP

 NAME:
	TAB_FORTOSPP
 PURPOSE:
	Procedure to convert a FORTRAN format to an SPP format specfication.

 CALLING SEQUENCE:
	sppformat, format, sppformat

 INPUTS:
	format - fortran format specification

 OUTPUTS:
	sppformat - sppformat specification

 HISTORY:
	version 1  D. Lindler   Jan, 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_fortospp.pro)

TAB_MODCOL

 NAME:
	TAB_MODCOL
 PURPOSE:
	Modify column description in a STSDAS table

 CALLING SEQUENCE:
	tab_modcol, tcb, column, units, format, newname

 INPUTS:
	tcb - table control block
	column - column name or number to be modified

 OPTIONAL INPUTS:
	units - string giving physical units for the column.
		If not supplied or set to the null string
		the units are not changed.
	format - print format (either fortran or SPP format)
		An spp format should be preceeded by a '%'.
		If not supplied or set to a null string, the
		print format for the column is not changed.
	newname - new name for the column.  If not supplied
		or set to a null string, the name is not
		changed
 EXAMPLES:

	change the wavelength column to WAVE with a new format
	of 'F10.3' and columns units of ANGSTROMS.

	   tab_modcol,tcb,'wavelength','ANGSTROMS','F10.3','WAVE'

	Change to print format of column 3 to spp format
	20.10e
	   tab_modcol,tcb,3,'','%20.10e'
 HISTORY:
	version 1  D. Lindler   Apr 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_modcol.pro)

TAB_NULL

 NAME:
	TAB_NULL  
 PURPOSE:
	function to locate null values within a vector of values from
	an STSDAS table.

 CALLING SEQUENCE
	result = tab_null(values)

 INPUTS:
	values - data value(s)

 OUTPUTS:
	a boolean variable is returned with the same length as values.
	1 indicates that the corresponding value was null

 OPERATIONAL NOTES:
	Boolean columns in an STSDAS table does not presently
	have the capability to flag null values.

 HISTORY:
	version 1   D. Lindler   April 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_null.pro)

TAB_NULLROW

 NAME:
	TAB_NULLROW 
 PURPOSE:
	Insert null row(s) into a STSDAS table

 CALLING SEQUENCE:
	tab_nullrow, tcb, tab, [ row1, row2  ]

 INPUTS:
	tcb - table control block

 INPUT/OUTPUTS:
	tab - table array

 OPTIONAL INPUTS:
	row1 - first row number to insert nulls (default=0)
	row2 - last row number to insert nulls (default = last row)

 HISTORY:
	version 1, D. Lindler  Apr 89
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_nullrow.pro)

TAB_PRINT

 NAME:
	TAB_PRINT 
 PURPOSE:
	Routine to print an stsdas table.

 CALLING SEQUENCE:
	tab_print, tcb, tab, columns, row1, row2

 INPUTS:
	tcb - table control block returned by TAB_READ
	tab - table array read by TAB_READ

 OPTIONAL INPUTS:
	columns - vector of column numbers to be printed or a string
		with column names separated by commas. If not supplied
		or set to the null string, all columns are printed.

	row1 - first row to print.  (default=0)
	row2 - last row to print.  (default=last row in table)

 SIDE EFFECTS:
	text is printed as directed by !textout

 HISTORY:
	version 1, D. Lindler  Apr 89
	April 90  Converted to NEW IDL D. Lindler
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_print.pro)

TAB_PUT

 NAME:
	TAB_PUT   
 PURPOSE:
	Procedure to place new values into a STSDAS table.

 CALLING SEQUENCE:
	tab_put, column, values, tcb, tab, row

 INPUTS:
	column - column name or number (if it is a new column then
		a column name must be specified)
	values - data values to add to the table

 INPUT/OUTPUTS:
	tcb - table control block
	tab - table array

 OPTIONAL INPUT:
	row - starting row to insert values

 HISTORY:
	version 1  D. Lindler   April 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_put.pro)

TAB_READ

 NAME:
   TAB_READ   
 PURPOSE:
   Procedure to read an SDAS table file
 CALLING SEQUENCE:
	tab_read,name,tcb,table,header
 INPUTS:
	name - name of the table file
 OUTPUTS:
	tcb - table control block 
		Longword array of size 16 x maxcols+2
		where maxcols is the maximum number of columns
		allocated for the table.
		tcb(*,0) contains:
		   word	0	SPARE
			1	number of user parameters
			2	max. number of user par. allowed
			3	number of rows in the table
			4	number of allocated rows (for col. ordered tab)
			5	number of columns defined
			6	max number of columns
			7	length of row used (in units of 2-bytes)
			8	max row length (in units of 2-bytes)
					relevant only for row ordered tables.
			9	table type (11 for row order, 12 for col. order)
			15	update flag (0-readonly, 1-update)
		tcb(*,i) contains description of column i
		   word 0	column number
			1	offset for start of row in units of 2-bytes
			2	width or column in 2-byte units
			3	data type
					6 = real*4
					7 = real*8
					4 = integer*4
					1 = boolean*4
					2 = character string
			4-8	ascii column name up to 19 characters
			9-13	column units (up to 19 characters)
			14-15	format string
		tcb(*,max number of columns+1)= file name

	table - table array, Byte array row length (bytes) x nrows

 	header - header parameters in form usable by sxpar, sxaddhist,
		sxaddpar, ect.
 HISTORY:
	Version 1  D. Lindler  Jan 88
	Converted to NEW IDL  April 90  D. Lindler
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_read.pro)

TAB_SIZE

 NAME:
	TAB_SIZE   
 PURPOSE:
	Routine to extract the table size from a table control block

 CALLING SEQUENCE:
	tab_size, tcb, nrows, ncols, maxrows, maxcols, rowlen, max_rowlen

 INPUTS:
	tcb - table control block

 OUTPUTS:
	nrows - number of rows in the table
	ncols - number of columns in the table
	maxrows - number of rows allocated
	maxcols - number of columns allocated
	rowlen - length of the rows in bytes
	max_rowlen - allocated row length

 HISTORY:
	version 1  D. Lindler  April 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_size.pro)

TAB_SORT

 NAME:
	TAB_SORT
 PURPOSE:
	Procedure to sort table by the specified column

 CALLING SEQUENCE:
	tab_sort, column, tcb, tab

 INPUTS:
	column - column name or number to sort on
	tcb - table control block

 INPUT/OUTPUTS:
	tab - table array

 HISTORY:
	version 1  D. Lindler  April 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_sort.pro)

TAB_SPPTOFOR

 NAME:
	TAB_SPPTOFOR  
 PURPOSE:
	This procedure converts an spp format specification to a normal
	Fortran format specification.

 CALLING SEQUENCE:
	tab_spptofor, sppformat, format, width

 INPUTS:
	sppformat - spp format specification (without preceeding %)

 OUTPUTS:
	forformat - fortran format specification (string)
	width - field width (integer)

 HISTORY:
	version 1  D. Lindler  Jan 1989
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_spptofor.pro)

TAB_VAL

 NAME:
	TAB_VAL
 PURPOSE:
	Routine to read a column from an SDAS table file

 CALLING SEQUENCE:
	values = tab_val( tcb, table, column, [ rows ] )
 INPUTS:
	tcb - table control block returned by tab_val
	table - table array returned by tab_val
	column - scalar column name or number
 OPTIONAL INPUT:
	rows - scalar giving row number or vector giving rows.
		If not supplied all rows are returned.
 OUTPUT:
	the values for the specified column (and rows) is returned
	as the function value.  If row is specified as a scalar
	(single row) then the result will be a scalar.
 HISTORY:
	version 1  D. Lindler  Jan. 1988
       Allow for a null column Landsman/Feggans    April 1992
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_val.pro)

TAB_WRITE

 NAME:
       TAB_WRITE
 PURPOSE:
       Routine to write an stsdas table to disk

 CALLING SEQUENCE:
       tab_write, name, tcb, tab, header

 INPUTS:
       name - file name (default extension = .tab)
       tcb - table control block
       tab - table array

 OPTIONAL INPUT:
       header - FITS header array

 HISTORY:
       version 1  D. Lindler   April 1989
       Converted to IDL V5.0   W. Landsman   September 1997
       Remove VMS-specific OPEN statement  W. Landsman  September 2006

(See $IDLUTILS_DIR/goddard/pro/sdas_table/tab_write.pro)

TAG_EXIST()

 NAME:        
       TAG_EXIST()
 PURPOSE:              
       To test whether a tag name exists in a structure.
 EXPLANATION:               
       Routine obtains a list of tagnames and tests whether the requested one
       exists or not. The search is recursive so if any tag names in the 
       structure are themselves structures the search drops down to that level.
       (However, see the keyword TOP_LEVEL).
               
 CALLING SEQUENCE: 
       status = TAG_EXIST(str, tag, [ INDEX =, /TOP_LEVEL, /QUIET ] )
    
 INPUT PARAMETERS:     
       str  -  structure variable to search
       tag  -  tag name to search for, scalar string

 OUTPUTS:
       Function returns 1b if tag name exists or 0b if it does not.
                              
 OPTIONAL INPUT KEYWORD:
       /TOP_LEVEL = If set, then only the top level of the structure is
                           searched.
       /QUIET - if set, then do not print messages if invalid parameters given
       /RECURSE - does nothing but kept for compatibility with the
                  Solarsoft version for which recursion is not the default 
        http://sohowww.nascom.nasa.gov/solarsoft/gen/idl/struct/tag_exist.pro
 OPTIONAL OUTPUT KEYWORD:
       INDEX = index of matching tag, scalar longward, -1 if tag name does
               not exist

 EXAMPLE:
       Determine if the tag 'THICK' is in the !P system variable
       
       IDL> print,tag_exist(!P,'THICK')

 PROCEDURE CALLS:
       None.

 MODIFICATION HISTORY:     : 
       Written,       C D Pike, RAL, 18-May-94               
       Passed out index of matching tag,  D Zarro, ARC/GSFC, 27-Jan-95     
       William Thompson, GSFC, 6 March 1996    Added keyword TOP_LEVEL
       Zarro, GSFC, 1 August 1996    Added call to help 
       Use SIZE(/TNAME) rather than DATATYPE()  W. Landsman  October 2001
       Added /RECURSE and /QUIET for compatibility with Solarsoft version
                W. Landsman  March 2009
       Slightly faster algorithm   W. Landsman    July 2009
       July 2009 update was not setting Index keyword  W. L   Sep 2009.
       Use V6.0 notation W.L. Jan 2012 
        Not setting index again, sigh  W.L./ K. Allers  Jan 2012

(See $IDLUTILS_DIR/goddard/pro/structure/tag_exist.pro)

TBDELCOL

 NAME:
       TBDELCOL
 PURPOSE:
       Delete a column of data from a FITS binary table

 CALLING SEQUENCE:
       TBDELCOL, h, tab, name

 INPUTS-OUPUTS
       h,tab - FITS binary table header and data array.  H and TAB will
               be updated with the specified column deleted

 INPUTS:
       name - Either (1) a string giving the name of the column to delete
                       or (2) a scalar giving the column number to delete

 EXAMPLE:
       Delete the column "FLUX" from FITS binary table test.fits

       IDL> tab = readfits('test.fits',h,/ext)    ;Read table
       IDL> tbdelcol, h, tab, 'FLUX'              ;Delete Flux column
       IDL> modfits,'test.fits',tab,h,/ext        ;Write back table

 PROCEDURES USED:
       SXADDPAR, TBINFO, TBSIZE
 REVISION HISTORY:                                           
       Written   W. Landsman        STX Co.     August, 1988
       Use new structure returned by TBINFO,  August, 1997
       Use SIZE(/TNAME) instead of DATATYPE()   October 2001
       Use /NOSCALE in call to TBINFO, update TDISP   W. Landsman   March 2007

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbdelcol.pro)

TBDELROW

 NAME:
	TBDELROW
 PURPOSE:
	Delete specified row or rows of data from a FITS binary table

 CALLING SEQUENCE:
	TBDELROW, h, tab, rows

 INPUTS-OUPUTS
	h,tab - FITS binary table header and data array.  H and TAB will
		be updated on output with the specified row(s) deleted.

	rows  -  scalar or vector, specifying the row numbers to delete
		First row has index 0.   If a vector it will be sorted and
		duplicates removed by TBDELROW

 EXAMPLE:
	Compress a table to include only non-negative flux values

	flux = TBGET(h,tab,'FLUX')       ;Obtain original flux vector
	bad = where(flux lt 0)           ;Find negative fluxes
	TBDELROW,h,tab,bad               ;Delete rows with negative fluxes

 PROCEDURE:
	Specified rows are deleted from the data array, TAB.  The NAXIS2
	keyword in the header is updated.

 REVISION HISTORY:                                           
	Written   W. Landsman        STX Co.     August, 1988
	Checked for IDL Version 2, J. Isensee, July, 1990
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbdelrow.pro)

TBGET

 NAME:
       TBGET
 PURPOSE:
       Return value(s) from specified column in a FITS binary table

 CALLING SEQUENCE
       values = TBGET( h, tab, field, [ rows, nulls, /NOSCALE] )
               or
       values = TBGET( tb_str, tab, field, [ rows, nulls, /NOSCALE] )

 INPUTS:
       h - FITS binary table header, e.g. as returned by FITS_READ
                       or
       tb_str - IDL structure extracted from FITS header by TBINFO.
               Use of the IDL structure will improve processing speed
       tab - FITS binary table array, e.g. as returned by FITS_READ
       field - field name or number, scalar

 OPTIONAL INPUTS:
       rows -  scalar or vector giving row number(s)
               Row numbers start at 0.  If not supplied or set to
               -1 then values for all rows are returned

 OPTIONAL KEYWORD INPUT:
       /NOSCALE - If this keyword is set and nonzero, then the TSCALn and
               TZEROn keywords will *not* be used to scale to physical values
               Default is to perform scaling
       CONTINUE - This keyword does nothing, it is kept for consistency with
               with earlier versions of TBGET().
 OUTPUTS:
       the values for the row are returned as the function value.
       Null values are set to 0 or blanks for strings.

 OPTIONAL OUTPUT:
       nulls - null value flag of same length as the returned data.
               Only used for integer data types, B, I, and J
               It is set to 1 at null value positions and 0 elsewhere.
               If supplied then the optional input, rows, must also
               be supplied.

 EXAMPLE:
       Read the columns labeled 'WAVELENGTH' and 'FLUX' from the second
       extension of a FITS file 'spectra.fits' into IDL vectors w and f

       IDL> fits_read,'spectra.fits',tab,htab,exten=2   ;Read 2nd extension
       IDL> w = tbget(htab,tab,'wavelength')
       IDL> f = tbget(htab,tab,'flux')

 NOTES:
       (1) If the column is variable length ('P') format, then TBGET() will 
       return the longword array of pointers into the heap area.   TBGET() 
       currently lacks the ability to actually extract the data from the 
       heap area.
       (2) Use the higher-level procedure FTAB_EXT (which calls TBGET()) to
       extract vectors directly from the FITS file.   
       (3) Use the procedure FITS_HELP to determine which extensions are 
       binary tables, and FTAB_HELP or TBHELP to determine the columns of the
       table
 PROCEDURE CALLS:
       TBINFO, TBSIZE 
 HISTORY:
       Written  W. Landsman        February, 1991
       Work for string and complex   W. Landsman         April, 1993
       Default scaling by TSCALn, TZEROn, Added /NOSCALE keyword,
       Fixed nulls output, return longword pointers for variable length
               binary tables,     W. Landsman  December 1996
       Added a check for zero width column  W. Landsman   April, 1997
       Add TEMPORARY() and REFORM() for speed  W. Landsman  May, 1997
       Use new structure returned by TBINFO    W. Landsman  August 1997
       Add IS_IEEE_BIG(), No subscripting when all rows requested
                               W. Landsman    March 2000
       Use SIZE(/TNAME) instead of DATATYPE()  W. Landsman October 2001
       Bypass IEEE_TO_HOST call for improved speed W. Landsman November 2002
       Cosmetic changes to SIZE() calls W. Landsman December 2002
       Added unofficial support for 64bit integers W. Landsman February 2003
       Support unsigned integers, new pointer types of TSCAL and TZERO
       returned by TBINFO   W. Landsman        April 2003
       Add an i = i[0] for V6.0 compatibility  W. Landsman  August 2003
       Use faster BYTEORDER byteswapping  W. Landsman April 2006
       Free pointers if FITS header supplied W. Landsman March 2007

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbget.pro)

TBHELP

 NAME:
       TBHELP
 PURPOSE:
       Routine to print a description of a FITS binary table header

 CALLING SEQUENCE:
       TBHELP, h, [TEXTOUT = ]

 INPUTS:
       h - FITS header for a binary table, string array

 OPTIONAL INPUT KEYWORD:
       TEXTOUT - scalar number (0-7) or string (file name) controling 
               output device (see TEXTOPEN).  Default is TEXTOUT=1, output 
               to the user's terminal    

 METHOD:
       FITS Binary Table keywords NAXIS*,EXTNAME,TFIELDS,TTYPE*,TFORM*,TUNIT*,
       are read from the header and displayed at the terminal

       A FITS header is recognized as bein for a binary table if the keyword 
       XTENSION has the value 'BINTABLE' or 'A3DTABLE'

 NOTES:
       Certain fields may be truncated in the display
 SYSTEM VARIABLES:
       Uses the non-standard system variables !TEXTOUT and !TEXTUNIT.   These
       are automatically defined by TBHELP if they have not been defined
       previously. 
 PROCEDURES USED:
       REMCHAR, SXPAR(), TEXTCLOSE, TEXTOPEN, ZPARCHECK 
 HISTORY:
       W. Landsman       February, 1991
       Parsing of a FITS binary header made more robust    May, 1992
       Added TEXTOUT keyword      August 1997
       Define !TEXTOUT if not already present   W. Landsman  November 2002
       Slightly more compact display   W. Landsman August 2005
       Fix Aug 2005 error omitting TFORM display W. Landsman Sep 2005

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbhelp.pro)

TBINFO

 NAME:
       TBINFO
 PURPOSE:
       Return an informational IDL structure from a FITS binary table header.

 CALLING SEQUENCE:
       tbinfo, h, tb_str, [ERRMSG = ]
 INPUTS:
       h - FITS binary table header, e.g. as returned by READFITS()

 OUTPUTS:
       tb_str - IDL structure with extracted info from the FITS binary table
               header.   Tags include
       .tbcol - starting column position in bytes, integer vector
       .width - width of the field in bytes, integer vector
       .idltype - idltype of field, byte vector
               7 - string, 4- real*4, 3-integer*4, 5-real*8
       .numval - repeat count, longword vector
       .tunit - string unit numbers, string vector
       .tnull - integer null value for the field, stored as a string vector
                 so that an empty string indicates that TNULL is not present
       .tform - format for the field, string vector
       .ttype - field name, string vector
       .maxval- maximum number of elements in a variable length array, long
               vector
       .tscal - pointer array giving the scale factor for converting to 
                physical values, default 1.0
       .tzero - pointer array giving the additive offset for converting to 
                physical values, default 0.0
       .tdisp - recommended output display format

       All of the output vectors will have same number of elements, equal
       to the number of columns in the binary table.

       The .tscal and .tzero values are stored as pointers so as to preserve
       the individual data types (e.g. float or double) which may differ 
       in different columns.   For example, to obtain the value of TSCAL for
       the third column use *tab_str.tscal[2]  
 OPTIONAL INPUT KEYWORD:
       /NOSCALE - if set, then the TSCAL* and TZERO* keywords are not extracted
            from the FITS header, and the .tscal and .tzero pointers do not
            appear in the output structure.
 OPTIONAL OUTPUT KEYWORD:
        ERRMSG = if present, then error messages are returned in this keyword
            rather than displayed using the MESSAGE facility 
 PROCEDURES USED:
       SXPAR()
 NOTES:
       For variable length ('P' format) column, TBINFO returns values for
       reading the 2 element longward array of pointers (numval=2, 
       idltype = 3, width=4)
 HISTORY:
       Major rewrite to return a structure      W. Landsman   August 1997
       Added "unofficial" 64 bit integer "K" format W. Landsamn Feb. 2003
       Store .tscal and .tzero tags as pointers, so as to preserve 
       type information   W. Landsman          April 2003
       Treat repeat count for string as specifying string length, not number
          of elements, added ERRMSG    W. Landsman        July 2006
       Treat logical as character string 'T' or 'F' W. Landsman  October 2006
       Added NOSCALE keyword  W. Landsman   March 2007

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbinfo.pro)

TBPRINT

 NAME:
       TBPRINT
  PURPOSE:
       Procedure to print specified columns & rows of a FITS binary table

 CALLING SEQUENCE:
       TBPRINT, h, tab, columns, [ rows, TEXTOUT =, FMT=, NUM_HEADER= ]
               or
       TBPRINT,tb_str, tab, columns, [ rows, TEXTOUT =, FMT=, NUM_HEADER =  ]

 INPUTS:
       h - FITS header for table, string array
                       or
       tb_str - IDL structure extracted from FITS header by TBINFO, useful 
           when TBPRINT is called many times with the same header
       tab - table array 
       columns - string giving column names, or vector giving
               column numbers (beginning with 1).  If string 
               supplied then column names should be separated by comma's.
               If set to '*' then all columns are printed in table format 
               (1 row per line, binary tables only).
       rows - (optional) vector of row numbers to print.  If
               not supplied or set to scalar, -1, then all rows
               are printed.

 OUTPUTS:
       None
 OPTIONAL INPUT KEYWORDS:
       FMT = Format string for print display.   If not supplied, then any 
               formats in the TDISP keyword fields of the table will be
               used, otherwise IDL default formats.   
       NUM_HEADER_LINES - Number of lines to display the column headers 
               default = 1).  By setting NUM_HEADER_LINES to an integer larger
               than 1, one can avoid truncation of the column header labels.  
               In addition, setting NUM_HEADER_LINES will display commented 
               lines indicating a FORMAT for reading the data, and a 
               suggested call to  readfmt.pro.
       NVAL_PER_LINE - The maximum number of values displayed from a multivalued
               column when printing in table format.   Default = 6
       TEXTOUT - scalar number (0-7) or string (file name) determining
               output device (see TEXTOPEN).  Default is TEXTOUT=1, output 
               to the user's terminal    
 SYSTEM VARIABLES:
       Uses nonstandard system variables !TEXTOUT and !TEXTOPEN
       Set !TEXTOUT = 3 to direct output to a disk file.   The system
       variable is overriden by the value of the keyword TEXTOUT

 EXAMPLES:
       tab = readfits('test.fits',htab,/ext) ;Read first extension into vars
       tbprint,h,tab,'STAR ID,RA,DEC'    ;print id,ra,dec for all stars
       tbprint,h,tab,[2,3,4],indgen(100) ;print columns 2-4 for 
                                          first 100 stars
       tbprint,h,tab,text="stars.dat"    ;Convert entire FITS table to
                                         ;an ASCII file named 'stars.dat'

 PROCEDURES USED:
       GETTOK(), STRNUMBER(), TEXTOPEN, TEXTCLOSE, TBINFO

 RESTRICTIONS: 
       (1) Program does not check whether output length exceeds output
               device capacity (e.g. 80 or 132).
       (2) Column heading may be truncated to fit in space defined by
               the FORMAT specified for the column.    Use NUM_HEADER_LINES
               to avoid truncation.
       (3) Program does not check for null values
       (4) Does not work with variable length columns
       (5) Will only the display the first value of fields with multiple values
        (unless there is one row each with the same number of mulitple values)
        If printing in table format (column='*') then up to 6 values
        can be printed per line.

 HISTORY:
       version 1  D. Lindler Feb. 1987
       Accept undefined values of rows,columns W. Landsman  August 1997
       Use new structure returned by TBINFO    W. Landsman  August 1997
       Made formatting more robust    W. Landsman   March 2000
       Use STRSPLIT to parse string column listing W. Landsman July 2002
       Wasn't always printing last row   W. Landsman  Feb. 2003
       Better formatting (space between columns) W. Landsman Oct. 2005
       Use case-insensitive match with TTYPE, use STRJOIN W.L. June 2006
       Fixed check for multiple values W.L. August 2006
       Fixed bad index value in August 2006 fix  W.L Aug 15 2006
       Free-up pointers after calling TBINFO  W.L. Mar 2007
       Add table format capability  W.L. Mar 2010
       Add NUM_HEADER_LINE keyword  P. Broos Apr 2010

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbprint.pro)

TBSIZE

 NAME:
       TBSIZE

 PURPOSE:
       Procedure to return the size of a FITS binary table.

 CALLING SEQUENCE:
       tbsize, h, tab, ncols, nrows, tfields, ncols_all, nrows_all

 INPUTS:
       h - FITS table header
       tab - FITS table array

 OUTPUTS:
       ncols - number of characters per row in table
       nrows - number of rows in table
       tfields - number of fields per row
       ncols_all - number of characters/row allocated (size of tab)
       nrows_all - number of rows allocated
 PROCEDURES USED:
       SXPAR()
 HISTORY
       D. Lindler  July, 1987
       Converted to IDL V5.0   W. Landsman   September 1997
       Remove obsolete !ERR call   W. Landsman   May 2000

(See $IDLUTILS_DIR/goddard/pro/fits_table/tbsize.pro)

TDB2TDT

 NAME:
   TDB2TDT

 AUTHOR:
   Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
   craigm@lheamail.gsfc.nasa.gov
   UPDATED VERSIONs can be found on my WEB PAGE: 
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

 PURPOSE:
   Relativistic clock corrections due to Earth motion in solar system 

 MAJOR TOPICS:
   Planetary Orbits

 CALLING SEQUENCE:
   corr = TDB2TDT(JD, TBASE=, DERIV=deriv)

 DESCRIPTION:

   The function TDB2TDT computes relativistic corrections that must
   be applied when performing high precision absolute timing in the
   solar system.

   According to general relativity, moving clocks, and clocks at
   different gravitational potentials, will run at different rates
   with respect to each other.  A clock placed on the earth will run
   at a time-variable rate because of the non-constant influence of
   the sun and other planets.  Thus, for the most demanding
   astrophysical timing applications -- high precision pulsar timing
   -- times in the accelerating earth observer's frame must be
   corrected to an inertial frame, such as the solar system
   barycenter (SSB).  This correction is also convenient because the
   coordinate time at the SSB is the ephemeris time of the JPL
   Planetary Ephemeris.

   In general, the difference in the rate of Ti, the time kept by an
   arbitrary clock, and the rate of T, the ephemeris time, is given
   by the expression (Standish 1998):

      dTi/dT = 1 - (Ui + vi^2/2) / c^2

   where Ui is the potential of clock i, and vi is the velocity of
   clock i.  However, when integrated, this expression depends on the
   position of an individual clock.  A more convenient approximate
   expression is:

     T = Ti + (robs(Ti) . vearth(T))/c^2 + dtgeo(Ti) + TDB2TDT(Ti)

   where robs is the vector from the geocenter to the observer;
   vearth is the vector velocity of the earth; and dtgeo is a
   correction to convert from the observer's clock to geocentric TT
   time.  TDB2TDT is the value computed by this function, the
   correction to convert from the geocenter to the solar system
   barycenter.

   As the above equation shows, while this function provides an
   important component of the correction, the user must also be
   responsible for (a) correcting their times to the geocenter (ie,
   by maintaining atomic clock corrections); (b) estimating the
   observatory position vector; and and (c) estimating earth's
   velocity vector (using JPLEPHINTERP).

   Users may note a circularity to the above equation, since
   vearth(T) is expressed in terms of the SSB coordinate time.  This
   appears to be a chicken and egg problem since in order to get the
   earth's velocity, the ephemeris time is needed to begin with.
   However, to the precision of the above equation, < 25 ns, it is
   acceptable to replace vearth(T) with vearth(TT).

   The method of computation of TDB2TDT in this function is based on
   the analytical formulation by Fairhead, Bretagnon & Lestrade, 1988
   (so-called FBL model) and Fairhead & Bretagnon 1990, in terms of
   sinusoids of various amplitudes.  TDB2TDT has a dominant periodic
   component of period 1 year and amplitude 1.7 ms.  The set of 791
   coefficients used here were drawn from the Princeton pulsar timing
   program TEMPO version 11.005 (Taylor & Weisberg 1989).

   Because the TDB2TDT quantity is rather expensive to compute but
   slowly varying, users may wish to also retrieve the time
   derivative using the DERIV keyword, if they have many times to
   convert over a short baseline.

 Verification

   This implementation has been compared against a set of FBL test
   data found in the 1996 IERS Conventions, Chapter 11, provided by
   T. Fukushima.  It has been verified that this routine reproduces
   the Fukushima numbers to the accuracy of the table, within
   10^{-14} seconds.

   Fukushima (1995) has found that the 791-term Fairhead & Bretagnon
   analytical approximation use here has a maximum error of 23
   nanoseconds in the time range 1980-2000, compared to a numerical
   integration.  In comparison the truncated 127-term approximation
   has an error of ~130 nanoseconds.


 PARAMETERS: 

   JD - Geocentric time TT, scalar or vector, expressed in Julian
        days.  The actual time used is (JD + TBASE).  For maximum
        precision, TBASE should be used to express a fixed epoch in
        whole day numbers, and JD should express fractional offset
        days from that epoch.


 KEYWORD PARAMETERS:

   TBASE - scalar Julian day of a fixed epoch, which provides the
           origin for times passed in JD.
          Default: 0

   DERIV - upon return, contains the derivative of TDB2TDT in units
           of seconds per day.  As many derivatives are returned as
           values passed in JD.


 RETURNS:
   The correction offset(s) in units of seconds, to be applied as
   noted above.


 EXAMPLE:

   Find the correction at ephemeris time 2451544.5 (JD):
     IDL> print, tdb2tdt(2451544.5d)
       -0.00011376314
   or 0.11 ms.


 REFERENCES:

   Princeton TEMPO Program
      http://pulsar.princeton.edu/tempo/

   FBL Test Data Set
      ftp://maia.usno.navy.mil/conventions/chapter11/fbl.results

   Fairhead, L. & Bretagnon, P. 1990, A&A, 229, 240
     (basis of this routine)

   Fairhead, L. Bretagnon, P. & Lestrade, J.-F. 1988, in *The Earth's
     Rotation and Reference Frames for Geodesy and Geodynamics*,
     ed. A. K. Babcock and G. A. Wilkins, (Dordrecht: Kluwer), p. 419
     (original "FBL" paper)

   Fukushima, T. 1995, A&A, 294, 895  (error analysis)

   Irwin, A. W. & Fukushima, T. 1999, A&A, 348, 642  (error analysis)

   Standish, E. M. 1998, A&A, 336, 381 (description of time scales)

   Taylor, J. H. & Weisberg, J. M. 1989, ApJ, 345, 434 (pulsar timing)


 SEE ALSO
   JPLEPHREAD, JPLEPHINTERP, JPLEPHTEST
   
 MODIFICATION HISTORY:
   Original logic from Fairhead & Bretagnon, 1990
   Drawn from TEMPO v. 11.005, copied 20 Jun 2001
   Documented and vectorized, 30 Jun 2001
   

  $Id: tdb2tdt.pro,v 1.4 2001/07/01 07:37:40 craigm Exp $

(See $IDLUTILS_DIR/goddard/pro/astro/tdb2tdt.pro)

TEN()

 NAME:
	TEN()
 PURPOSE:
	Converts a sexigesimal number or string to decimal.
 EXPLANATION:
	Inverse of the SIXTY() function.

 CALLING SEQUENCES:
	X = TEN( [ HOUR_OR_DEG, MIN, SEC ] )
	X = TEN( HOUR_OR_DEG, MIN, SEC )
	X = TEN( [ HOUR_OR_DEG, MIN ] )
	X = TEN( HOUR_OR_DEG, MIN )
	X = TEN( [ HOUR_OR_DEG ] )      <--  Trivial cases
	X = TEN( HOUR_OR_DEG )          <--

        or
       X = TEN(HRMNSC_STRING)

 INPUTS:
	HOUR_OR_DEG,MIN,SEC -- Scalars giving sexigesimal quantity in 
		in order from largest to smallest.    
                         or
       HRMNSC_STRING - String giving sexigesmal quantity separated by
               spaces or colons e.g. "10 23 34" or "-3:23:45.2"
               Any negative values should begin with a minus sign.
 OUTPUTS:
	Function value returned = double real scalar, decimal equivalent of
	input sexigesimal quantity.  A minus sign on any nonzero element
	of the input vector causes all the elements to be taken as
	< 0.

 EXAMPLES:
       IDL> print,ten(0,-23,34)
                 --> -0.39277778
       IDL> print,ten("-0:23:34")
                 --> -0.39277778
 PROCEDURE:
	Mostly involves checking arguments and setting the sign.

	The procedure TENV can be used when dealing with a vector of 
	sexigesimal quantities.

 MODIFICATION HISTORY:
	Written by R. S. Hill, STX, 21 April 87       
	Modified to allow non-vector arguments.  RSH, STX, 19-OCT-87
       Recognize -0.0   W. Landsman/B. Stecklum   Dec 2005
       Work with string input  W. Landsman Dec 2008

(See $IDLUTILS_DIR/goddard/pro/astro/ten.pro)

TENV()

 NAME:
	TENV()
 PURPOSE:
	Converts sexigesimal number or string vector to decimal.  
 EXPLANATION:
	Like TEN() but allows vector input.

 CALLING SEQUENCES:
	Result = TENV( dd, mm )           ; result = dd + mm/60.
	Result = TENV( dd, mm, ss)        ; result = dd + mm/60. + ss/3600.
                       or
       Result = TENV(ddmmss_string)
 INPUTS:
	dd - Sexigesimal element(s) corresponding to hours or degrees
	mm - Sexigesimal element(s) corresponding to minutes
	ss - Sexigesimal element(s) corresponding to seconds (optional)
		The input parameters can be scalars or vectors.   However, the
		number of elements in each parameter must be the same.

       HRMNSC_STRING - String scalar or vector giving sexigesmal quantity 
               separated by spaces or colons e.g. "10 23 34" or "-3:23:45.2"
               Any negative values should begin with a minus sign.
 OUTPUTS:
	Result -  double, decimal equivalent of input sexigesimal 
		quantities.  Same number of elements as the input parameters.
		If the nth element in any of the input parameters is negative 
		then the nth element in Result will also be negative.

 EXAMPLE:
	If dd = [60,60,0], and mm = [30,-30,-30], then

	IDL> Result = TENV(dd,mm)  ====>   Result =  [60.5,-60.5,-0.5]
       
       Alternatively, the input could be written as the string vector
       IDL> str = ['60:30','-60:30','-0:30'] 
       IDL> print,tenv(str)   ====>   Result =  [60.5,-60.5,-0.5]

 WARNING: 
       TENV() will recognize floating point values of -0.0 as negative numbers.
       However,  there is no distinction in the binary representation of -0 
       and 0  (integer values), and so TENV will treat both values as positive.
 PROCEDURES USED:
       GETTOK(), REPCHR()  for string processing.
 PROCEDURE:
	Mostly involves checking arguments and setting the sign.

   MODIFICATION HISTORY:
	Written by W.B. Landsman           April, 1991
       Recognize -0.0   W. Landsman/B. Stecklum   Dec 2005
       Work with string input   W. Landsman Feb 2009

(See $IDLUTILS_DIR/goddard/pro/astro/tenv.pro)

TEXTCLOSE

 NAME:
	TEXTCLOSE                   

 PURPOSE:
	Close a text outpu file previously opened with TEXTOPEN 
 EXPLANATION:
	procedure to close file for text output as specifed
	by the (non-standard) system variable !TEXTOUT. 

 CALLING SEQUENCE:
	textclose, [ TEXTOUT = ]

 KEYWORDS:
	textout - Indicates output device that was used by
		TEXTOPEN

 SIDE EFFECTS:
	if !textout is not equal to 5 and the textunit is
	opened.   Then unit !textunit is closed and released

 HISTORY:
	D. Lindler  Dec. 1986  (Replaces PRTOPEN)
	Test if TEXTOUT is a scalar string   W. Landsman   August 1993
 Can't close unit -1 (Standard Output) I. Freedman  April  1994
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/textclose.pro)

TEXTOPEN

NAME:
TEXTOPEN
PURPOSE:
Open a device specified by TEXTOUT with unit !TEXTUNIT
EXPLANATION:
Procedure to open file for text output. The type of output
device (disk file or terminal screen) is specified by the
TEXTOUT keyword or the (nonstandard) system variable !TEXTOUT.

CALLING SEQUENCE:
textopen, program, [ TEXTOUT =, /STDOUT, /SILENT, MORE_SET=, WIDTH= ]

INPUTS:
program - scalar string giving name of program calling textopen

OPTIONAL INPUT KEYWORDS:
TEXTOUT - Integer scalar (0-7) specifying output file/device to be
opened (see below) or scalar string giving name of output file.
If TEXTOUT is not supplied, then the (non-standard) system
variable !TEXTOUT is used.
/SILENT - By default, TEXTOPEN prints an informational message when
opening a file for hardcopy output. Set /SILENT (or !QUIET)
to suppress this message.
/STDOUT - if this keyword is set and non-zero, then the standard output
(unit = -1) is used for TEXTOUT=1 or TEXTOUT=2. The use
of STDOUT has 2 possible advantages:
(1) the output will appear in a journal file
(2) Many Unix machines print spurious control characters when
printing to /dev/tty. These characters are eliminated by
setting /STDOUT

The disadvantage of /STDOUT is that the /MORE option is not
available.

WIDTH - Specify line width for hardcopy output line wrapping (passed onto OPENW).

OPTIONAL OUTPUT KEYWORD:
MORE_SET - Returns 1 if the output unit was opened with /MORE. This
occurs if (1) TEXTOUT = 1 and (2) the device is a tty, and
(3) /STDOUT is not set. User can use the returned value
of MORE_SET to determine whether to end output when user
presses 'Q'.
SIDE EFFECTS:
The following dev/file is opened for output. Different effects
occur depending whether the standard output is a GUI (Macintosh,
Windows, Unix/IDLTool) or a TTY

textout=0 Nowhere
textout=1 if a TTY then TERMINAL using /more option
otherwise standard (Unit=-1) output
textout=2 if a TTY then TERMINAL without /more option
otherwise standard (Unit=-1) output
textout=3 <program>.prt
textout=4 laser.tmp
textout=5 user must open file
textout=7 same as 3 but text is appended to <program>.prt
file if it already exists.
textout = filename (default extension of .prt)

The unit to be opened is obtained with the procedure GET_LUN
unless !TEXTOUT=5. The unit number is placed in system variable
!TEXTUNIT. For !TEXTOUT=5 the user must set !TEXTUNIT to the
appropriate unit number.

NOTES:
When printing to a TTY terminal, the output will *not* appear in an
IDL JOURNAL session, unlike text printed with the PRINT command.

NON-STANDARD SYSTEM VARIABLES:
TEXTOPEN will automatically define the following system variables if
they are not previously defined:

DEFSYSV,'!TEXTOUT',1
DEFSYSV,'!TEXTUNIT',0
HISTORY:
D. Lindler Dec. 1986
Keyword textout added, J. Isensee, July, 1990
Made transportable, D. Neill, April, 1991
Trim input PROGRAM string W. Landsman Feb 1993
Don't modify TEXTOUT value W. Landsman Aug 1993
Modified for MacOS I. Freedman April 1994
Modified for output terminals without a TTY W. Landsman August 1995
Added /STDOUT keyword W. Landsman April 1996
added textout=7 option, D. Lindler, July, 1996
Exit with RETURN instead of RETALL W. Landsman June 1999
In IDL V5.4 filepath(/TERMINAL) not allowed in the IDLDE WL August 2001
Added MORE_SET output keyword W.Landsman January 2002
Added /SILENT keyword W. Landsman June 2002
Define !TEXTOUT and !TEXTUNIT if needed. R. Sterner, 2002 Aug 27
Return Calling Sequence if no parameters supplied W.Landsman Nov 2002
Remove VMS specific code W. Landsman Sep 2006
Make sure MORE_SET is always defined W. Landsman Jan 2007
Added WIDTH keyword J. Bailin Nov 2010
Use V6.0 notation W. Landsman April 2011

(See $IDLUTILS_DIR/goddard/pro/misc/textopen.pro)

TICLABELS

 NAME:
	TICLABELS
 PURPOSE:
	Create tic labels for labeling astronomical images.
 EXPLANATION: 
	Used to display images with right ascension or declination
	axes.  This routine creates labels for already determined tic
	marks (every other tic mark by default)

 CALLING SEQUENCE:
	TICLABELS, minval, numtics, incr, ticlabs, [ RA = ,DELTA = ]

 INPUTS:
	minval  - minimum value for labels (degrees)
	numtics - number of tic marks
	incr    - increment in minutes for labels

 OUTPUTS:
	ticlabs - array of charater string labels

 OPTIONAL INPUT KEYWORDS:
	/RA - if this keyword is set then the grid axis is assumed to be
		a Right Ascension.   Otherwise a declination axis is assumed
	DELTA - Scalar specifying spacing of labels.   The default is 
		DELTA = 2 which means that a label is made for every other tic
		mark.  Set DELTA=1 to create a label for every tic mark.
       FONT - scalar font graphics keyword (-1,0 or 1) for text

 PROCEDURES USED:
	RADEC

 RESTRICTIONS:
	Invalid for wide field (> 2 degree) images since it assumes that a 
	fixed interval in Y (or X) corresponds to a fixed interval in Dec 
	(or RA)

 REVISON HISTORY:
	written by B. Pfarr, 4/15/87
	Added DELTA keywrd for compatibility with IMCONTOUR W. Landsman Nov 1991
	Added nicer hms and dms symbols when using native PS fonts Deutsch 11/92
	Added Patch for bug in IDL <2.4.0 as explained in NOTES E. Deutsch 11/92
	Fix when crossing 0 dec or 24h RA
	Fix DELTA keyword so that it behaves according to the documentation
			W. Landsman  Hughes STX,  Nov 95  
       Allow sub arcsecond formatting  W. Landsman   May 2000
       Better formatting for non-unity DELTA values  W. Landsman July 2004
       Allow FONT keyword to be passed.  T. Robishaw Apr. 2006
       Write 0h rather than 24h  W. L. August 2008
       Fix problem when tic values is exactly 0 degrees   Mar 2012

(See $IDLUTILS_DIR/goddard/pro/astro/ticlabels.pro)

TICPOS

 NAME:
       TICPOS
 PURPOSE:
       Specify distance between tic marks for astronomical coordinate overlays
 EXPLANATION:
       User inputs number an approximate distance
       between tic marks, and the axis length in degrees.  TICPOS will return 
       a distance between tic marks such that the separation is a round
       multiple in arc seconds, arc minutes, or degrees

 CALLING SEQUENCE:
       TICPOS, deglen, pixlen, ticsize, incr, units

 INPUTS:
       deglen - length of axis in DEGREES
       pixlen - length of axis in plotting units (pixels)
       ticsize - distance between tic marks (pixels).  This value will be
               adjusted by TICPOS such that the distance corresponds to
               a round multiple in the astronomical coordinate.

 OUTPUTS:
       ticsize - distance between tic marks (pixels), positive scalar 
       incr    - incremental value for tic marks in round units given 
               by the UNITS parameter
       units - string giving units of ticsize, either 'ARC SECONDS',
               'ARC MINUTES', or 'DEGREES'

 EXAMPLE:
       Suppose a 512 x 512 image array corresponds to 0.2 x 0.2 degrees on
       the sky.   A tic mark is desired in round angular units, approximately 
       every 75 pixels.

       IDL> ticsize = 75
       IDL> TICPOS,0.2,512,ticsize,incr,units   

       ==> ticsize = 85.333, incr = 2. units = 'Arc Minutes'

       i.e. a good tic mark spacing is every 2 arc minutes, corresponding
       to 85.333 pixels.

 REVISON HISTORY:
       written by W. Landsman            November, 1988
       Converted to IDL V5.0   W. Landsman   September 1997
       Don't use all capital letters  W. Landsman May 2003
       Fix case where incr crosses degree/minute or minute/degree boundary
               A. Mortier/W.Landsman April 2005

(See $IDLUTILS_DIR/goddard/pro/astro/ticpos.pro)

TICS

 NAME:
       TICS
 PURPOSE:
       Compute a nice increment between tic marks for astronomical images.
 EXPLANATION:       
       For use in labelling a displayed image with right ascension
       or declination axes.  An approximate distance between tic 
       marks is input, and a new value is computed such that the 
       distance between tic marks is in simple increments of the 
       tic label values.

 CALLING SEQUENCE:
       tics, radec_min, radec_max, numx, ticsize, incr, [ /RA ]

 INPUTS:
       radec_min - minimum axis value (degrees)
       radec_max - maximum axis value (degrees)
       numx  - number of pixels in x direction

 INPUT/OUTPUT  
       ticsize - distance between tic marks (pixels)

 OUTPUTS:
       incr    - incremental value for tic labels (in minutes of 
               time for R.A., minutes of arc for dec.)

 REVISON HISTORY:
       written by B. Pfarr, 4/14/87
       Added some more tick precision (i.e. 1 & 2 seconds in case:) EWD May92
       Added sub arcsecond tick precision   W. Landsman   May 2000
       Plate scale off by 1 pixel  W. Landsman July 2004

(See $IDLUTILS_DIR/goddard/pro/astro/tics.pro)

TIC_ONE

 NAME:
	TIC_ONE
 PURPOSE:
	Determine the position of the first tic mark for astronomical images.
 EXPLANATION:
	For use in labelling images with right ascension
	and declination axes. This routine determines the 
	position in pixels of the first tic.

 CALLING SEQUENCE:
	tic_one, zmin, pixx, incr, min2, tic1, [RA = ]

 INPUTS:
	zmin  - astronomical coordinate value at axis zero point (degrees 
		or hours)
	pixx - distance in pixels between tic marks (usually obtained from TICS)
	incr - increment in minutes for labels (usually an even number obtained 
		from the procedure TICS)

 OUTPUTS:
	min2 - astronomical coordinate value at first tic mark 
	tic1 - position in pixels of first tic mark

 EXAMPLE:
	Suppose a declination axis has a value of 30.2345 degrees at its
	zero point.  A tic mark is desired every 10 arc minutes, which 
	corresponds to 12.74 pixels.  Then

	IDL> TIC_ONE, 30.2345, 1, 12.74, min2, tic1

	yields values of min2 = 30.333 and tic1 = 5.74, i.e. the first tic
	mark should be labeled 30 deg 20 minutes and be placed at pixel value
	5.74

 REVISION HISTORY:
	by B. Pfarr, 4/15/87
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/astro/tic_one.pro)

TO_HEX

 NAME:
       TO_HEX
 PURPOSE:
       Translate a non-negative decimal integer to a hexadecimal string
 CALLING SEQUENCE:
       HEX = TO_HEX( D, [ NCHAR ] )
 INPUTS:
       D - non-negative decimal integer, scalar or vector.  If input as a
           string, (e.g. '32') then all leading blanks are removed.

 OPTIONAL INPUT:
       NCHAR - number of characters in the output hexadecimal string.
               If not supplied, then the hex string will contain no 
               leading zeros.

 OUTPUT:
       HEX - hexadecimal translation of input integer, string

 EXAMPLES:
       IDL> A = TO_HEX([11,16])    ==>   A = ['B','10']
       IDL> A = TO_HEX(100,3) ==>   A = '064'

 METHOD:
       The hexadecimal format code '(Z)' is used to convert.  No parameter
       checking is done.
 PROCEDURES CALLED:
       None.
 REVISION HISTORY:
       Written   W. Landsman         November, 1990
       Converted to IDL V5.0   W. Landsman   September 1997
       Use FSTRING() for more than 1024 values      March 2000 
       Assume since  V5.4, omit FSTRING() call      April 2006

(See $IDLUTILS_DIR/goddard/pro/misc/to_hex.pro)

TRANSFORM_COEFF()

 NAME:
    TRANSFORM_COEFF()
 PURPOSE:
    Compute new polynomial coefficients under a linear transformation 
 EXPLANATION:
     Suppose one has a (nonlinear) polynomial (similar to the POLY() function)
          y = C[0] + C[1]*x  + C[2]*x^2 + C[3]*x^3 + ...

      and one has a linear transformation in X

          x = alpha*x' + beta
     This function computes the new polynomial coefficients under the linear
     transformation. 

 CALLING SEQUENCE:
     newcoeff = TRANSFORM_COEFF( coeff, alpha, beta)
 INPUTS:
     Coeff  -  vector of polynomial coefficients (as with POLY()).    The 
         degree of the polynomial is N_elements(coeff) - 1
     Alpha, Beta - numeric scalars defining the linear transformation in X 
 OUTPUTS:
    NewCoeff - Vector (same size as Coeff) giving the new polyomial 
               coefficients
 EXAMPLE:
     Suppose one has polynomial mapping a nonlinear distortion in the X 
     direction of a spectrum

     y = 0.2 + 1.1*x + 0.1*x^2

     if one rebins the spectrum to half the size then the linear transformation
     is  x = 2.*x'
     so alpha = 2 and beta = 0
     The new coefficients are
     IDL> print, transform_coeff([0.2,1.1,0.1],2.,0) 
     ==> [0.2, 2.2, 0.4] 
 METHOD:
    Performs a binomial expansion of the polynomial and collect like terms
    groups.google.com/group/comp.lang.idl-pvwave/msg/11132d96d9c0f93d?hl=en&
 REVISION HISTORY:
   Written   W. Landsman          December 2007

(See $IDLUTILS_DIR/goddard/pro/math/transform_coeff.pro)

TRAPZD

 NAME:
       TRAPZD
 PURPOSE:
       Compute the nth stage of refinement of an extended trapezoidal rule.
 EXPLANATION:
       This procedure is called by QSIMP and QTRAP.   Algorithm from Numerical
       Recipes, Section 4.2.   TRAPZD is meant to be called iteratively from
       a higher level procedure.

 CALLING SEQUENCE:
       TRAPZD, func, A, B, S, step, [ _EXTRA = ]

 INPUTS:
       func - scalar string giving name of function to be integrated.   This
               must be a function of one variable.
       A,B -  scalars giving the limits of the integration

 INPUT-OUTPUT:
       S -    scalar giving the total sum from the previous iterations on 
               input and the refined sum after the current iteration on output.

       step - LONG scalar giving the number of points at which to compute the
               function for the current iteration.   If step is not defined on
               input, then S is intialized using the average of the endpoints
               of limits of integration.

 OPTIONAL INPUT KEYWORDS:
       Any supplied keywords will be passed to the user function via the 
       _EXTRA facility. 

 NOTES:
       (1) TRAPZD will check for math errors (except for underflow) when 
       computing the function at the endpoints, but not on subsequent 
       iterations.

       (2) TRAPZD always uses double precision to sum the function values
       but the call to the user-supplied function is double precision only if 
       one of the limits A or B is double precision.
 REVISION HISTORY:
       Written         W. Landsman                 August, 1991
       Always use double precision for TOTAL       March, 1996
       Pass keyword to function via _EXTRA facility  W. Landsman July 1999
       Don't check for floating underflow  W.Landsman  April 2008

(See $IDLUTILS_DIR/goddard/pro/math/trapzd.pro)

TSC

 NAME:
       TSC

 PURPOSE:
       Interpolate an irregularly sampled field using a Triangular Shaped Cloud

 EXPLANATION:
       This function interpolates an irregularly sampled field to a
       regular grid using Triangular Shaped Cloud (nearest grid point
       gets weight 0.75-dx^2, points before and after nearest grid
       points get weight 0.5*(1.5-dx)^2, where dx is the distance
       from the sample to the grid point in units of the cell size).

 CATEGORY:
       Mathematical functions, Interpolation

 CALLING SEQUENCE:
       Result = TSC, VALUE, POSX, NX[, POSY, NY, POSZ, NZ, 
                     AVERAGE = average, WRAPAROUND =  wraparound,
                     ISOLATED = isolated, NO_MESSAGE = no_message]

 INPUTS:
       VALUE: Array of sample weights (field values). For e.g. a
              temperature field this would be the temperature and the
              keyword AVERAGE should be set. For e.g. a density field
              this could be either the particle mass (AVERAGE should
              not be set) or the density (AVERAGE should be set).
       POSX:  Array of X coordinates of field samples, unit indices: [0,NX>.
       NX:    Desired number of grid points in X-direction.
       
 OPTIONAL INPUTS:
      POSY: Array of Y coordinates of field samples, unit indices: [0,NY>.
      NY:   Desired number of grid points in Y-direction.
      POSZ: Array of Z coordinates of field samples, unit indices: [0,NZ>.
      NZ:   Desired number of grid points in Z-direction.

 KEYWORD PARAMETERS:
       AVERAGE:    Set this keyword if the nodes contain field samples
                   (e.g. a temperature field). The value at each grid
                   point will then be the weighted average of all the
                   samples allocated to it. If this keyword is not
                   set, the value at each grid point will be the
                   weighted sum of all the nodes allocated to it
                   (e.g. for a density field from a distribution of
                   particles). (D=0). 
       WRAPAROUND: Set this keyword if you want the first grid point
                   to contain samples of both sides of the volume
                   (see below).
       ISOLATED:   Set this keyword if the data is isolated, i.e. not
                   periodic. In that case total `mass' is not conserved.
                   This keyword cannot be used in combination with the
                   keyword WRAPAROUND.
       NO_MESSAGE: Suppress informational messages.

 Example of default allocation of nearest grid points: n0=4, *=gridpoint.

     0   1   2   3     Index of gridpoints
     *   *   *   *     Grid points
   |---|---|---|---|   Range allocated to gridpoints ([0.0,1.0> --> 0, etc.)
   0   1   2   3   4   posx

 Example of ngp allocation for WRAPAROUND: n0=4, *=gridpoint.

   0   1   2   3         Index of gridpoints
   *   *   *   *         Grid points
 |---|---|---|---|--     Range allocated to gridpoints ([0.5,1.5> --> 1, etc.)
   0   1   2   3   4=0   posx


 OUTPUTS:
       Prints that a TSC interpolation is being performed of x
       samples to y grid points, unless NO_MESSAGE is set.

 RESTRICTIONS:
       Field data is assumed to be periodic with the sampled volume
       the basic cell, unless ISOLATED is set.
       All input arrays must have the same dimensions.
       Postition coordinates should be in `index units' of the
       desired grid: POSX=[0,NX>, etc.
       Keywords ISOLATED and WRAPAROUND cannot both be set.

 PROCEDURE:
       Nearest grid point is determined for each sample.
       TSC weights are computed for each sample.
       Samples are interpolated to the grid.
       Grid point values are computed (sum or average of samples).

 EXAMPLE:
       nx=20
       ny=10
       posx=randomu(s,1000)
       posy=randomu(s,1000)
       value=posx^2+posy^2
       field=tsc(value,posx*nx,nx,posy*ny,ny,/average)
       surface,field,/lego

 NOTES:
       Use csc.pro or ngp.pro for lower order interpolation schemes.    A 
       standard reference for these interpolation methods is:   R.W. Hockney 
       and J.W. Eastwood, Computer Simulations Using Particles (New York: 
       McGraw-Hill, 1981).

 MODIFICATION HISTORY:
       Written by Joop Schaye, Feb 1999.
       Check for overflow for large dimensions  P. Riley/W. Landsman Dec. 1999

(See $IDLUTILS_DIR/goddard/pro/math/tsc.pro)

TSUM

 NAME:
       TSUM
 PURPOSE:
       Trapezoidal summation of the area under a curve. 
 EXPLANATION:
       Adapted from the procedure INTEG in the IUE procedure library.  

 CALLING SEQUENCE:
       Result = TSUM(y)
              or
       Result = TSUM( x, y, [ imin, imax ] )  
 INPUTS:
       x = array containing monotonic independent variable.  If omitted, then
               x is assumed to contain the index of the y variable.
               x = lindgen( N_elements(y) ).
       y = array containing dependent variable y = f(x)

 OPTIONAL INPUTS:
       imin = scalar index of x array at which to begin the integration
               If omitted, then summation starts at x[0].
       imax = scalar index of x value at which to end the integration 
               If omitted then the integration ends at x[npts-1].

 OUTPUTS:
       result = area under the curve y=f(x) between x[imin] and x[imax].

 EXAMPLE:
       IDL> x = [0.0,0.1,0.14,0.3] 
       IDL> y = sin(x)
       IDL> print,tsum(x,y)    ===>  0.0445843
       
       In this example, the exact curve can be computed analytically as 
       1.0 - cos(0.3) = 0.0446635     
 PROCEDURE:
       The area is determined of individual trapezoids defined by x[i],
       x[i+1], y[i] and y[i+1].

       If the data is known to be at all smooth, then a more accurate
       integration can be found by interpolation prior to the trapezoidal
       sums, for example, by the standard IDL User Library int_tabulated.pro.
 MODIFICATION HISTORY:
       Written, W.B. Landsman, STI Corp. May 1986
       Modified so X is not altered in a one parameter call Jan 1990
       Converted to IDL V5.0   W. Landsman   September 1997
       Allow non-integer values of imin and imax  W. Landsman April 2001
       Fix problem if only 1 parameter supplied W. Landsman June 2002

(See $IDLUTILS_DIR/goddard/pro/math/tsum.pro)

TVBOX

 NAME:
      TVBOX
 PURPOSE:
      Draw a box(es) or rectangle(s) of specified width
 EXPLANATION: 
      Positions can be specified either by the cursor position or by 
      supplying a vector of X,Y positions.  By default, TVBOX now
     (since Jan 2012) assumes data coordinates if !X.crange is set. 

 CALLING SEQUENCE:
      TVBOX, width, [ x, y, color, /DATA, ANGLE= ,COLOR =, _EXTRA =  ]

 INPUTS:
      WIDTH -  either a scalar giving the width of a box, or a 2 element
               vector giving the length and width of a rectangle.

 OPTIONAL INPUTS:           
      X  -  x position for box center, scalar or vector
      Y  -  y position for box center, scalar or vector.   If vector, then Y
            must have the same number of elements as X
            Positions are specified in device coordinates unless /DATA is set
            If X and Y are not specified, and device has a cursor, then 
            TVBOX will draw a box at current cursor position
      COLOR - String or integer specifying the color  to draw the box(es)
            If COLORS is a scalar then all boxes are drawn with the same
            color value.   Otherwise, the Nth box is drawn with the
            Nth value of color.    Color can also be specified as 
            string (e.g.'red').   See cgCOLOR for a list of available
            color names.     Default = "opposite".    
 OUTPUTS:
      None

 OPTIONAL KEYWORD INPUTS:
      ANGLE - numeric scalar specifying the clockwise rotation of
              the boxes or rectangles.
      COLOR - Scalar or vector, overrides the COLOR input parameter
              Color can be specified as a string (e.g. 'red') or intensity 
              value. See cgCOLOR() for a list of color names.       
               Default = 'opposite' (i.e. color opposite the background).   
      /DATA - if this keyword is set and non-zero, then the box width and
              X,Y position center are interpreted as being in DATA 
              coordinates.   Note that data coordinates must be previously
              defined (with a PLOT or CONTOUR call).   The default
              is to assume data coordinates if !X.CRANGE is set.    Force
              device coordinates by setting DATA = 0 or /DEVICE
      /DEVICE Set this keyword to force use of device coordinates
      /FILL  - If set, fill the box using cgCOLORFILL
      /SQUARE - If set, then a square is drawn, even if in data coordinates
               with unequal X and Y axes.   The X width is used for the
               square width, and the Y width is ignored.

      Any keyword recognized by cgPLOTS (or cgCOLORFILL if /FILL is set) 
      is also recognized by TVBOX.   
      In particular, the linestyle, thickness and clipping of the boxes
      is controlled by the  LINESTYLE, THICK and NOCLIP keywords.
      (Clipping is turned off by default, set NOCLIP=0 to activate it.)
      If /FILL is set then available keywords include LINE_FILL and 
      FILL_PATTERN. 

 SIDE EFFECTS:
       A square or rectangle will be drawn on the device
       For best results WIDTH should be odd when using the default DEVICE
       coordinates.  (If WIDTH is even, the actual size of the box will be 
       WIDTH + 1, so that box remains centered.)

 EXAMPLES:
       (1) Draw a double thick box of width 13, centered at 221,256 in the
       currently active window

           IDL> tvbox, 13, 221, 256, thick=2

       (2) Overlay a "slit" with dimension 52" x 2" on a previously displayed
           image at a position angle (East of North) of 32 degrees.    The 
           slit is to be centered at XC, YC and the plate scale 
           arcsec_per_pixel is known.

           IDL> w = [2.,52.]/arcsec_per_pixel ;Convert slit size to pixel units
           IDL> tvbox,w,XC,YC,ang=-32          ;Draw slit
 RESTRICTIONS:
         Allows use of only device (default) or data (if /DATA is set) 
           coordinates.   Normalized coordinates are not allowed
 PROCEDURES USED:
       cgpolygon, zparcheck
 REVISON HISTORY:
       Written, W. Landsman   STX Co.           10-6-87
       Modified to take vector arguments. Greg Hennessy Mar 1991
       Fixed centering of odd width    W. Landsman    Sep. 1991
       Let the user specify COLOR=0, accept vector color, W. Landsman Nov. 1995
       Fixed typo in _EXTRA keyword  W. Landsman   August 1997
       Added ANGLE keyword    W.Landsman     February 2000 
       Make sure ANGLE is a scalar   W. Landsman  September 2001
       Don't round coordinates if /DATA is set.   M. Perrin  August 2005
       Use STRICT_EXTRA to flag valid keywords W. Landsman Sep 2005
       Check that width has only 1 or 2 elements W. Landsman August 2010
       Use Coyote Graphcis  W. Landsman February 2011
       Added /FILL keyword  W. Landsman  July 2011
       Default to data coordinates if !X.crange present  WL Jan 2012
       Added Square keyword  WL.  April 2012

(See $IDLUTILS_DIR/goddard/pro/tv/tvbox.pro)

TVCIRCLE

 NAME:
     TVCIRCLE
 PURPOSE:
     Draw circle(s) of specified radius at specified position(s) 
 EXPLANATION: 
     If a position is not specified, and device has a cursor, then a circle
     is drawn at the current cursor position.    By default, TVCIRCLE now
     (since Jan 2012) assumes data coordinates if !X.crange is set.

 CALLING SEQUENCE:
     TVCIRCLE, rad, x, y, color, [ /DATA, /FILL, _EXTRA  =  ]         

 INPUTS:
     RAD - radius of circle(s) to be drawn, positive numeric scalar

 OPTIONAL INPUT:
      X - x position for circle center, vector or scalar
      Y - y position for circle center, vector or scalar
               If X and Y are not specified, and the device has a cursor, 
               then program will draw a circle at the current cursor position
      COLOR -  color name or intensity value(s) (0 - !D.N_COLORS) used to draw
               the circle(s).   If COLOR is a scalar then all circles are drawn
               with the same color value.   Otherwise, the Nth circle is drawn
               with the  Nth value of color.  See cgCOLOR() for a list of color
               names.  Default = 'opposite' (i.e. color opposite the 
               background).   

 OPTIONAL KEYWORD INPUTS:
       /DATA - if this keyword is set and non-zero, then the circle width and
              X,Y position center are interpreted as being in DATA 
              coordinates.   Note that data coordinates must be previously
              defined (with a PLOT or CONTOUR call).    TVCIRCLE will
              internally convert to device coordinates before drawing the
              circle, in order to maintain optimal smoothness.    The default
              is to assume data coordinates if !X.CRANGE is set.    Force
              device coordinates by setting DATA = 0 or /DEVICE
       /DEVICE - If set, then force use of device coordinates..
       /FILL  - If set, fill the circle using cgCOLORFILL

               Any keyword recognized by cgPLOTS (or cgCOLORFILL if /FILL is 
               set) is also recognized by TVCIRCLE.   In particular, the color,
               linestyle, thickness and clipping of the circles are controlled
               by the  COLOR, LINESTYLE, THICK and NOCLIP keywords.  (Clipping
               is turned off by default, set NOCLIP=0 to activate it.)
               If /FILL is set then available keywords are LINE_FILL and 
               FILL_PATTERN. 
 OUTPUTS:
       None

 RESTRICTIONS:
       (1) Some round-off error may occur when non-integral values are 
           supplied for both the radius and the center coordinates
       (2) TVCIRCLE does not accept /NORMAL coordinates.
       (3) TVCIRCLE always draws a circle --- even when in data coordinates 
           and the X and Y data scales are unequal.    (The X data scale is 
           used to define the circle radius.)     If this is not the behaviour
           you want, then use TVELLIPSE instead.
 EXAMPLE:
       (1) Draw circles of radius 9 pixels at the positions specified by 
           X,Y vectors, using double thickness lines

           IDL> tvcircle, 9, x, y, THICK = 2

           Now fill in the circles using the LINE_FILL method

           IDL> tvcircle, 9, x, y, /FILL, /LINE_FILL
 METHOD:
           The method used is that of Michener's, modified to take into account
           the fact that IDL plots arrays faster than single points.   See
           "Fundamental of Interactive Computer Graphics" by Foley and Van Dam"
           p. 445 for the algorithm.

 REVISON HISTORY:
           Original version   written by B. Pfarr  STX   10-88 
           Major rewrite adapted from CIRCLE by Allyn Saroyan   LNLL
           Wayne Landsman   STX     Sep. 91
           Added DATA keyword   Wayne Landsman  HSTX    June 1993
           Added FILL keyword.  R. S. Hill, HSTX, 4-Nov-1993
           Always convert to device coords, add _EXTRA keyword, allow vector
           colors.   Wayne Landsman, HSTX,  May 1995
           Allow one to set COLOR = 0,   W. Landsman, HSTX, November 1995
           Check if data axes reversed.  P. Mangifico, W. Landsman  May 1996
           Use strict_extra to check input keywords W. Landsman  July 2005
           Update documentation to note NOCLIP=0 option W.L.  Oct. 2006
           Make all integers default to LONG  W. Landsman  Dec 2006
           Use Coyote Graphics procedures W. Landsman Feb 2011
           Default to data coordinates if !X.crange present  WL Jan 2012
           Add /DEVICE coords, fix Jan 2012 update.   Mar 2012

(See $IDLUTILS_DIR/goddard/pro/tv/tvcircle.pro)

TVELLIPSE

 NAME:
      TVELLIPSE

 PURPOSE:
      Draw an ellipse on the current graphics device.

 CALLING SEQUENCE:
      TVELLIPSE, rmax, rmin, xc, yc, [ pos_ang, color, COLOR= ,/DATA, NPOINTS=
                                        LINESTYLE=, THICK=, /MAJOR, /MINOR ]
 INPUTS:
       RMAX,RMIN - Scalars giving the semi-major and semi-minor axes of
                   the ellipse
 OPTIONAL INPUTS:
       XC,YC - Scalars giving the position on the TV of the ellipse center
               If not supplied (or if XC, YC are negative and /DATA is not 
               set), and an interactive graphics device (e.g. not postscript)
               is set,  then the user will be prompted for X,Y
       POS_ANG - Position angle of the major axis, measured counter-clockwise
                 from the X axis.  Default is 0.
       COLOR - Scalar  integer or string specifying color to draw ellipse.   
               See cgcolor.pro for a list of possible color names

 OPTIONAL KEYWORD INPUT:
        COLOR - Intensity value or color name used to draw the circle, 
                overrides parameter value.  Default = 'opposite'
                See cgCOLOR() for a list of color names.;        
       /DATA - if this keyword is set and non-zero, then the ellipse radii and
               X,Y position center are interpreted as being in DATA
               coordinates.   Note that the data coordinates must have been
               previously defined (with a PLOT or CONTOUR call).  The default
              is to assume data coordinates if !X.CRANGE has been set by a 
              previous plot.    Force device coordinates by setting DATA = 0.
        /DEVICE - Set to force use of device coordinates.
        /FILL - If set, then fill the ellipse using cgCOLORFILL
        NPOINTS - Number of points to connect to draw ellipse, default = 120
                  Increase this value to improve smoothness
        /MAJOR - Plot a line along the ellipse's major axis
        /MINOR - Plot a line along the ellipse's minor axis

               Any keyword recognized by cgPLOTS is also recognized by TVELLIPSE.
               In particular, the color, linestyle, thickness and clipping of
               the ellipses are controlled by the  COLOR, LINESTYLE, THICK and
               NOCLIP keywords.  (Clipping is turned off by default, set
               NOCLIP=0 to activate it.)  If /FILL is set then available 
               keywords include LINE_FILL and FILL_PATTERN. 

 RESTRICTIONS:
        TVELLIPSE does not check whether the ellipse is within the boundaries
        of the window.

        The ellipse is evaluated at NPOINTS (default = 120) points and
        connected by straight lines, rather than using the more sophisticated
        algorithm used by TVCIRCLE

        TVELLIPSE does not accept normalized coordinates.

        TVELLIPSE is not vectorized; it only draws one ellipse at a time

 EXAMPLE:
        Draw an ellipse of semi-major axis 50 pixels, minor axis 30
        pixels, centered on (250,100), with the major axis inclined 25
        degrees counter-clockwise from the X axis.  Use a double thickness
        line and device coordinates

	IDL> tvellipse,50,30,250,100,25,thick=2,/device

 NOTES:
        Note that the position angle for TVELLIPSE (counter-clockwise from
        the X axis) differs from the astronomical position angle
        (counter-clockwise from the Y axis).

 REVISION HISTORY:
        Written  W. Landsman STX          July, 1989
        Converted to use with a workstation.  M. Greason, STX, June 1990
        LINESTYLE keyword, evaluate at 120 points,  W. Landsman HSTX Nov 1995
        Added NPOINTS keyword, fixed /DATA keyword W. Landsman HSTX Jan 1996
        Check for reversed /DATA coordinates  P. Mangiafico, W.Landsman May 1996
        Work correctly when X & Y data scales are unequal  December 1998
        Removed cursor input when -ve coords are entered with /data
        keyword set  P. Maxted, Keele, 2002
        Use _EXTRA keywords including NOCLIP  W. Landsman October 2006
        Add plotting of major and minor axes and /MAJOR, /MINOR keywords;
        fixed description of RMAX,RMIN (semi-axes).  J. Guerber Feb. 2007
        Update to use Coyote graphics W. Landsman Feb 2011
        Default to data coordinates if a previous plot has been made 
        (X.crange is non-zero)  W. Landsman Jan 2012
        Added /DEVICE keyword W. Landsman   Mar 2012
        Added /FILL keyword  W. Landsman Mar 2012

(See $IDLUTILS_DIR/goddard/pro/tv/tvellipse.pro)

TVLASER

 NAME:
      TVLASER
 PURPOSE:
      Prints screen or image array onto a Postscript file or printer.
      Information from FITS header is optionally used for labeling.  

 CALLING SEQUENCE:     
      TVLASER, [header, Image, BARPOS = ,CARROWS =, CLABELS = ,/COLORPS, 
             COMMENTS = ,CSIZE = ,CTITLE = , DX = , DY =, /ENCAP, FILENAME =
             HEADER = ,/HELP, IMAGEOUT = ,/INTERP, /MAGNIFY, /NoCLOSE, 
             /NoDELETE, /NO_PERS_INFO, /NoEIGHT, /NoPRINT, /NoRETAIN, 
             /PORTRAIT, PRINTER = , /REVERSE, /SCALE, TITLE = , /TrueColor, 
             XDIM=, XSTART=, YDIM=, YSTART=, BOTTOMDW=, NCOLORSDW= ]	

       Note that the calling sequence was changed in May 1997
 OPTIONAL INPUTS: 
       HEADER - FITS header string array.   Object and astrometric info from
               the FITS header will be used for labeling, if available
       IMAGE - if an array is passed through this parameter, then this image
               will be used rather than reading off the current window.  This
		allows easy use of large images.     It is usually preferable
               to optimally byte scale IMAGE before supplying it to TVLASER   

 OPTIONAL KEYWORD INPUT PARAMETERS: 
       BARPOS - A four- or five-element vector giving the position and
            orientation of the color bar.  The first four elements
            [X0,Y0,XSize,YSize] indicate the position and size of the color
            bar in INCHES, relative to origin of the displayed image.
            (X0,Y0) are the position of the lower left corner and 
            (XSize,YSize) are the width and height.  The fifth element is
            optional, and if present, the color bar will be printed
            horizontally rather than vertically.  If BARPOS is set to
            anything but a four- or five-element vector, the bar is NOT
            printed.  The default value is BARPOS = [-0.25, 0.0, 0.2, 2.0] 
       BOTTOMDW - The lowest value to use in building the density
            wedge.  Used with NCOLORSDW.  Compatible with BOTTOM and
            NCOLORS keywords of XLOADCT.
       CARROWS - The color to print the North-East arrows.  Default is dark.
            Three types of values can be passed:
                 SCALAR: that value's color in the current color table
                 3-ELEMENT VECTOR: the color will be [R,G,B]
                 STRING: A letter indicating the color.  Valid names are:  
                 'W' (white), 'D' (dark/black), 'R' (red),    'G' (green), 
                 'B' (blue),  'T' (turquoise),  'V' (violet), 'Y' (yellow), 
             If the keyword is set to a value of -1, the arrows are
             NOT printed.
       COLORPS - If present and non-zero, the idl.ps file is written using
             color postscript.
       COMMENTS - A string that will be included in the comment line below the
                image.  For multi-line comments you can either use "!C" in the
                string as a carriage return {although the vertical spacing
                might be a little off} or, preferably, make the COMMENTS a
                string array with each line as a separate element. 
       CLABELS - Color to print the labels, same format as for CARROWS.
       CSIZE - Color to print the size-scale bar and label, same format as for
                CARROWS.
       CTITLE - Color to print the title, same format as for CARROWS.
       DX,DY - offsets in INCHES added to the position of the figure on the
               paper.  As is the case for the device keywords XOFFSET and
               YOFFSET, when in landscape mode DX and DY are the same
               *relative to the paper*, not relative to the plot (e.g., DX is
               the horizontal offset in portrait mode, but the *vertical*
               offset in landscape mode).
       ENCAP - If present and non-zero, the IDL.PS file is written in
               encapsulated postscript for import into LaTeX documents
       FILENAME - scalar string giving name of output postscript file.
               Default is idl.ps.   Automatically sets /NODELETE
       HEADER = FITS header.   This is an alternative to supplying the FITS
                header in the first parameter.
       HELP - print out the sytax for this procedure.
       INTERP - If present and non-zero, current color table will be
                interpolated to fill the full range of the PostScript color
                table (256 colors).  Otherwise, the current color table will be
                directly copied.   You probably will want to use this if you
                are using IMAGE keyword and a shared color table.
       MAGNIFY - The net magnification of the entire figure.  At this point,
                the figure is not automatically centered on the paper if the
                value of MAGNIFY is not equal to 1, but the DX and DY keywords
                can be used to shift location.  For example, to fit a full plot
                on the printable area (8.5x8.5 inches) of the Tek PhaserIISD
                color printer use:  MAGNIFY=0.8, DX=0.5, DY=0.5.;       
       NCOLORSDW - The number of values to include in the density
                wedge.  Used with BOTTOMDW.  Compatible with
                BOTTOM/NCOLORS keywords of XLOADCT.
       NoCLOSE - If present and non-zero, then the postscript file is not
             closed (or printed), the device is set to 'PS', and the data 
             coordinate system is set to match the image size.  This allows the
             user to add additional plotting commands before printing.  For 
             example, to include a 15 pixel circle around a source at 
             coordinates (150,160), around an image, im, with FITS header 
             array, h

                IDL> tvlaser,h,im,/NoClose      ;Write image & annotation
                IDL> tvcircle,15,150,160,/data  ;Draw circle
                IDL> device,/close              ;Close postscript file & print

       NoDELETE - If present and non-zero, the postscript file is kept AND is 
                 also sent to the printer
       NoEIGHT - if set then only four bits sent to printer (saves space)
       NO_PERS_INFO - if present and non-zero, output notation will NOT
                 include date/user block of information.
       NoPRINT - If present and non-zero, the output is sent to a file (default
                name 'idl.ps'), which is NOT deleted and is NOT sent to the 
                printer.
       NoRETAIN - In order to avoid possible problems when using TVRD with
                 an obscured window, TVLASER will first copy the current window
                 to a temporary RETAIN=2 window.    Set /NORETAIN to skip this
                 step and improve performance
       PORTRAIT - if present and non-zero, the printer results will be in
                 portrait format; otherwise, they will be in landscape format.
                 If labels are requested, image will be in portrait mode,
                 regardless
       PRINTER - scalar string giving the OS command to send a the postscript
               file to the printer.   Under Unix, the default value of PRINTER
               is 'lpr ' while for other OS it is 'print ' 
       REVERSE - if present and non-zero, color table will be fliped, so black
               and white are reversed.
       SCALE - if present and non-zero, image will be bytscaled before being
               sent to postscript file.      
       TITLE - if present and non-zero, the string entered here will be the
               title of the picture.  Default is the OBJECT field in the
               header (if present).
       TRUECOLOR - if present and non-zero, the postscript file is created
               using the truecolor switch (i.e. true=3). The colorbar is
               not displayed in this mode.  
       XDIM,YDIM - Number of pixels.  Default is from !d.x_size and !d.y_size,
               or size of image if passed with IMAGE keyword.
       XSTART,YSTART - lower left corner (default of (0,0))

 OPTIONAL KEYWORD OUTPUT PARAMETER
        IMAGEOUT = the image byte array actually sent to the postscript file.

 SIDE EFFECTS: 
        A postscript file is created in the current directory.  User must have 
        write privileges in the current directory.  The file is named idl.ps
        unless the FILENAME keyword is given.   The file is directed to the
        printer unless the /ENCAP, /NoCLOSE, or /NOPRINT keywords are given.
        After printing, the file is deleted unless the /NODELETE or FILENAME 
        keywords are given. 
 PROCEDURE:  
       Read display or take IMAGE and then redisplay into a postscript file.
       If a header exists, printout header information.  If header has
       astrometry, then print out orientation and scale information.
 PROCEDURES USED:
        ARROWS, EXTAST, FDECOMP, GETROT, PIXCOLOR, SXPAR(), XYAD, ZPARCHECK

*EXAMPLE:
       1) Send a true color image (xsize,ysize,3) to a printer (i.e. print23l),
                tvlaser,huv,cpic,/colorps,/truecolor,printer="print23l"
                % TVLASER: Now printing image: $print23l idl.ps

 MODIFICATION HISTORY:     
       Major rewrite from UIT version   W. Landsman   Dec 94
       Massive rewrite.  Added North-East arrows, pixel scale bar, color bar,
       and keywords DX, DY, MAGNIFY, INTERP, HELP, and COMMENTS.
       Created ablility to define colors for annotation and
       text.  Repositioned text labels.     J.Wm.Parker, HITC, 5/95
       Make Header and Image parameters instead of keywords.   Add PRINTER
       keyword.   Include alternate FITS keywords.   W. Landsman May 97      
       Copy to a RETAIN=2 window, work without FITS header W. Landsman June 97
       Cleaner output when no astrometry in header  W. Landsman  June 97
       Added /INFO to final MESSAGE  W. Landsman   July 1997
       12/4/97	jkf/acc	- added TrueColor optional keyword.
       Added /NoClose keyword, trim Equinox format  W. Landsman 9-Jul-1998
       Don't display coordinate labels if no astrometry, more flexible
       formatting of exposure time W. Landsman 30-Aug-1998
       BottomDW and NColorsDW added.  R. S. Hill, 1-Mar-1999
       Apply func tab to color bar if not colorps.  RSH, 21 Mar 2000
       Fix problem with /NOCLOSE and unequal X,Y sizes  W. Landsman Feb 2001
       Use TVRD(True=3) if /TRUECOLOR set    W. Landsman   November 2001
       More synonyms, check for header supplied W. Landsman November 2007

(See $IDLUTILS_DIR/goddard/pro/tv/tvlaser.pro)

TVLIST

 NAME:
	TVLIST
 PURPOSE:
	Cursor controlled listing of image pixel values in a window. 

 CALLING SEQUENCE:
	TVLIST, [image, dx, dy, TEXTOUT=, OFFSET= , ZOOM= ]

 OPTIONAL INPUTS:
	IMAGE - Array containing the image currently displayed on the TV.
		If omitted, the byte pixel intensities are read from the TV
		If the array does not start at position (0,0) on the window then
		the OFFSET keyword should be supplied.

	DX     -Integer scalar giving the number of pixels in the X direction 
		to be displayed.  If omitted then DX = 18 for byte images, and 
		DX = 14 for integer images.  TVLIST will display REAL data 
		with more significant figures if more room is availble to 
		print.  

	DY    - Same as DX, but in Y direction.  If omitted, then DY = DX 

 OPTIONAL INPUT KEYWORDS:
      OFFSET - 2 element vector giving the location of the image pixel (0,0) 
		on the window display.   OFFSET can be positive (e.g if the 
		image is centered in a larger window) or negative (e.g. if the
		only the central region of an image much larger than the window
		is being displayed. 
		Default value is [0,0], or no offset.
	ZOOM - Scalar specifying the magnification of the window with respect
		to the image variable.    Use, for example, if image has been
		REBINed before display.
	TEXTOUT - Optional keyword that determines output device.
		The following dev/file is opened for output.

		textout=1	TERMINAL using /more option (default)
		textout=2	TERMINAL without /more option
		textout=3	<program>.prt  
		textout=4	laser.tmp
		textout=5       user must open file
		textout=7	Append to an existing <program>.prt file if it
				exists
		textout = filename (default extension of .prt)

	If TEXTOUT > 3 or set to a filename, then TVLIST will prompt for a 
	brief description to be included in the output file
 OUTPUTS:
	None.
 PROCEDURE:
	Program prompts user to place cursor on region of interest in 
	image display.  Corresponding region of image is then displayed at
	the terminal.   A compression factor between the image array and the
	displayed image is determined using the ratio of image sizes.  If 
	necessary, TVLIST will divide all pixel values in a REAL*4 image by a 
	(displayed) factor of 10^n (n=1,2,3...) to make a pretty format.

 SYSTEM VARIABLE:
	The nonstandard system variable !TEXTOUT is used as an alternative to
	the keyword TEXTOUT.   The procedure ASTROLIB can be used to define
	!TEXTOUT (and !TEXTUNIT) if necessary.

 RESTRICTIONS:
	TVLIST may not be able to correctly format all pixel values if the
	dynamic range near the cursor position is very large.

       Probably does not work under Mac IDL which does not allow the cursor
       to be positioned with TVCRS
 PROCEDURES CALLED:
	IMLIST, UNZOOM_XY
 REVISION HISTORY:
	Written by rhc, SASC Tech, 3/14/86.
	Added textout keyword option, J. Isensee, July, 1990
	Check for readable pixels     W. Landsman   May 1992
	Use integer format statement from F_FORMAT    W. Landsman   Feb 1994
	Added OFFSET, ZOOM keywords  W. Landsman   Mar 1996
	More intelligent formatting of longword, call TEXTOPEN with /STDOUT
		W. Landsman  April, 1996
	Added check for valid dx value  W. Landsman   Mar 1997
	Converted to IDL V5.0   W. Landsman   September 1997
       Major rewrite to call IMLIST, recognize new integer data types
                                           W. Landsman Jan 2000
       Remove all calls to !TEXTUNIT   W. Landsman   Sep 2000
       Always call UNZOOM_XY for MOUSSE compatibility  W. Landsman Sep. 2004

(See $IDLUTILS_DIR/goddard/pro/tv/tvlist.pro)

T_APER

 NAME:
       T_APER
 PURPOSE:
       Driver procedure (for APER) to compute concentric aperture photometry.
 EXPLANATION:
       Data is read from and written to disk FITS ASCII tables.   
       Part of the IDL-DAOPHOT photometry sequence

 CALLING SEQUENCE:
       T_APER, image, fitsfile, [ apr, skyrad, badpix, PRINT=, NEWTABLE=, 
                       /EXACT, /SILENT, SETSKYVAL = ]

 INPUTS:
       IMAGE   - input data array
       FITSFILE  - disk FITS ASCII table name (from T_FIND).  Must contain
               the keywords 'X' and 'Y' giving the centroid of the source
               positions in FORTRAN (first pixel is 1) convention.   An
               extension of .fit is assumed if not supplied.

 OPTIONAL INPUTS:
       User will be prompted for the following parameters if not supplied.

       APR    -  Vector of up to 12 REAL photometry aperture radii.
       SKYRAD  - Two element vector giving the inner and outer radii
               to be used for the sky annulus
       BADPIX  - Two element vector giving the minimum and maximum
               value of a good pixel (Default [-32765,32767])

 OPTIONAL KEYWORDS INPUTS:
       /EXACT - If this keyword is set, then intersection of the circular
               aperture is computed exactly (and slowly) rather than using
               an approximation.   See APER for more info.
       /PRINT - if set and non-zero then NSTAR will also write its results to
               a file aper.prt.   One can specify a different output file 
               name by setting PRINT = 'filename'.
       /SILENT - If this keyword is set and non-zero, then APER will not
               display photometry results at the screen, and the results 
               will be automatically incorporated in the FITS table without
               prompting the user
       NEWTABLE  - Name of output disk FITS ASCII table, scalar string.   
               If not supplied, then the input FITSFILE will be updated with 
               the aperture photometry results.
       SETSKYVAL - Use this keyword to force the sky to a specified value 
               rather than have APER compute a sky value.    SETSKYVAL 
               can either be a scalar specifying the sky value to use for 
               all sources, or a 3 element vector specifying the sky value, 
               the sigma of the sky value, and the number of elements used 
               to compute a sky value.   The 3 element form of SETSKYVAL
               is needed for accurate error budgeting.

 PROMPTS:
       T_APER requires the number of photons per analog digital unit
       (PHPADU), so that it can compute Poisson noise statistics to assign
       photometry errors.    It first tries to find the PHPADU keyword in the
       original image header, and if not found will look for the GAIN, 
       CCDGAIN and finally ATODGAIN keywords.   If still not found, T_APER 
       will prompt the user for this value.

 PROCEDURES:
       APER, FTADDCOL, FTGET(), FTINFO, FTPUT, READFITS(), SXADDPAR, 
       SXPAR(), WRITEFITS 
 REVISON HISTORY:
       Written   W. Landsman   ST Systems Co.            May 1988
       Store results as flux or magnitude                August 1988
       Added SILENT keyword  W. Landsman                 Sep. 1991
       Changed ERR SKY to ERR_SKY W. Landsman   March 1996
       Replace TEXTOUT keyword with PRINT keyword  W. Landsman  May 1996
       Check CCDGAIN or ATODGAIN keywords to find phpadu W. Landsman May 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Updated for new FTINFO calling sequence   W. Landsman  May 2000
       Added /EXACT keyword                      W. Landsman  June 2000

(See $IDLUTILS_DIR/goddard/pro/idlphot/t_aper.pro)

T_FIND

 NAME:
        T_FIND
 PURPOSE:
       Driver procedure (for FIND) to locate stars in an image.
 EXPLANATION:
       Finds positive brightness perturbations (i.e stars) in a 
       2 dimensional image.  Output is to a FITS ASCII table.

 CALLING SEQUENCE:
       T_FIND, image, im_hdr, [ fitsfile, hmin, fwhm, sharplim, roundlim, 
                                       PRINT = , /SILENT ]
 INPUTS:
       image - 2 dimensional image array (integer or real) for which one
               wishes to identify the stars present
       im_hdr - FITS header associated with image array

 OPTIONAL INPUTS: 
       T_FIND will prompt for these parameters if not supplied

       fitsfile - scalar string specifying the name of the output FITS ASCII
               table file
       fwhm - FWHM to be used in the convolving filter
       hmin - Threshold intensity for a point source - should generally
               be 3 or 4 sigma above background level
       sharplim - 2 element vector giving low and high Limit for 
               sharpness statistic (Default: [0.2,1.0] )
       roundlim - 2 element vector giving low and high Limit for
               roundness statistic (Default: [-1.0,1.0] )

 OPTIONAL INPUT KEYWORDS:
       /PRINT - if set and non-zero then NSTAR will also write its results to
               a file find.prt.   One can specify the output file name by
               setting PRINT = 'filename'.
       /SILENT -   If this keyword is set and non-zero, then FIND will work
               silently, and not display each star found

 OUTPUTS:
       None

 PROCEDURES CALLED:
       CHECK_FITS, FDECOMP, FIND, FTADDCOL, FTCREATE, SXADDHIST, SXADDPAR, 
       SXDELPAR, SXPAR(), WRITEFITS

 REVISION HISTORY:
       Written W. Landsman, STX  May, 1988
       Added phpadu, J. Hill, STX, October, 1990
       New calling syntax output to disk FITS table, W. Landsman    May 1996
       Work with more than 32767 stars  W. Landsman August 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Remove obsolete !ERR system variable   W. Landsman   May 2000

(See $IDLUTILS_DIR/goddard/pro/idlphot/t_find.pro)

T_GETPSF

 NAME:
       T_GETPSF
 PURPOSE:
       Driver procedure (for GETPSF) to generate a PSF from isolate stars.
 EXPLANATION:
       Generates a point-spread function from one or more isolated stars.
       List of stars is read from the FITS ASCII table output of T_APER.
       PSF is represented as a sum of a Gaussian plus residuals.
       Ouput residuals are written to a FITS image file.

 CALLING SEQUENCE:
       T_GETPSF, image, fitsfile, [ idpsf, psfrad, fitrad, psfname, 
                                       /DEBUG, NEWTABLE =]

 INPUTS:
       IMAGE - image array
       FITSFILE  - scalar string giving name of disk FITS ASCII table.  Must 
               contain the keywords 'X','Y' (from T_FIND) and 'AP1_MAG','SKY'
               (from T_APER).

 OPTIONAL INPUTS:
       IDPSF - vector of stellar ID indices indicating which stars are to be 
               used to create the PSF.    Not that the PSF star should be 
               specified *not* by its STAR_ID value, but rather by the its 
               row number (starting with 0) in the FITS table
       PSFRAD - the radius for which the PSF will be defined
       FITRAD - fitting radius, always smaller than PSFRAD
       PSFNAME - name of FITS image file to contain PSF residuals,
               scalar string
       GETPSF will prompt for all the above values if not supplied.

 OPTIONAL KEYWORD INPUT
       NEWTABLE - scalar string specifying the name of the output FITS ASCII
               table.   If not supplied, then the input table is updated with
               the keyword PSF_CODE, specifying which stars were used for the
               PSF.
       DEBUG - if this keyword is set and non-zero, then the result of each
               fitting iteration will be displayed.

 PROMPTS:
       T_GETPSF will prompt for the readout noise (in data numbers), and
       the gain (in photons or electrons per data number) so that pixels can
       be weighted during the PSF fit.   To avoid the prompt, add the 
       keywords RONOIS and PHPADU to the FITS ASCII table header.     

 PROCEDURES USED:
       FTADDCOL, FTGET(), FTPUT, GETPSF, READFITS(), SXADDHIST, SXADDPAR, 
       SXPAR(), WRITEFITS, ZPARCHECK
 REVISION HISTORY:
       Written  W. Landsman     STX           May, 1988
       Update PSF_CODE to indicate PSF stars in order used, W. Landsman Mar 96
       I/O to FITS ASCII disk files  W. Landsman    May 96
       Converted to IDL V5.0   W. Landsman   September 1997
       Update for new FTINFO call   W. Landsman   May 2000

(See $IDLUTILS_DIR/goddard/pro/idlphot/t_getpsf.pro)

T_GROUP

 NAME:
	T_GROUP
 PURPOSE:
	Driver procedure (for GROUP) to place stars in non-overlapping groups.
 EXPLANATION:
	This procedure is part of the DAOPHOT sequence that places star
	positions with non-overlapping PSFs into distinct groups   
	Input and output are to FITS ASCII tables

 CALLING SEQUENCE:
	T_GROUP, fitsfile, [ rmax, XPAR = , YPAR = , NEWTABLE = ]

 INPUTS:
	FITSFILE -  Name of disk FITS ASCII table containing the X,Y positions
		in FITS (FORTRAN) convention (first pixel is 1,1)

 OPTIONAL INPUTS:
	rmax - maximum allowable distance between stars in a single group

 OPTIONAL INPUT KEYWORDS:
	XPAR, YPAR - scalar strings giving the field name in the output table
		containing the X and Y coordinates.   If not supplied,
		then the fields 'X' and 'Y' are read.
	NEWTABLE - scalar giving name of output disk FITS ASCII table.   If not
		supplied, 

 PROCEDURES:
	FTADDCOL, FTGET(), FTINFO, FTPUT, GROUP, READFITS(), SXADDHIST, 
	SXADDHIST, WRITEFITS
 REVISION HISTORY:
	Written, W. Landsman        STX Co.      May, 1996
	Converted to IDL V5.0   W. Landsman   September 1997
       Updated for new FTINFO call    W. Landsman    May 2000

(See $IDLUTILS_DIR/goddard/pro/idlphot/t_group.pro)

T_NSTAR

 NAME:
       T_NSTAR
 PURPOSE:
       Driver procedure (for NSTAR) for simultaneous PSF fitting.  
 EXPLANATION:
       Input and output are to disk FITS ASCII tables.

 CALLING SEQUENCE:
       T_NSTAR, image, fitsfile, [psfname, groupsel, /SILENT, /PRINT
                               NEWTABLE = , /VARSKY ]
 INPUTS:
       IMAGE - 2-d image array
       FITSFILE  - scalar string giving name of disk FITS ASCII table.  Must 
               contain the keywords 'X','Y' (from T_FIND) 'AP1_MAG','SKY'
               (from T_APER) and 'GROUP_ID' (from T_GROUP).   This table
               will be updated with the results of T_NSTAR, unless the 
               keyword NEWTABLE is supplied.   

 OPTIONAL INPUTS:
       PSFNAME - Name of the FITS file created by T_GETPSF containing
               PSF residuals, scalar string
       GROUPSEL - Scalar or vector listing the groups to process.  For
               example, to process stars in groups 2 and 5 set
               GROUPSEL = [2,5].  If omitted, or set equal to -1,
               then NSTAR will process all groups.

 OPTIONAL KEYWORD INPUTS:
       VARSKY - If this keyword is set and non-zero, then the mean sky level
               in each group of stars, will be fit along with the brightness
               and positions.
       /SILENT - if set and non-zero, then NSTAR will not display its results
               at the terminal
       /PRINT - if set and non-zero then NSTAR will also write its results to
               a file NSTAR.PRT.   One can specify the output file name by
               setting PRINT = 'filename'.
       NEWTABLE  - Name of output disk FITS ASCII table to contain the results
               of NSTAR.   If not supplied, then the input FITSFILE will be 
               updated.  
       DEBUG - if this keyword is set and non-zero, then the result of each
               fitting iteration will be displayed.

 PROCEDURES CALLED:
       FTADDCAL, FTINFO, FTGET(), FTPUT, NSTAR, SXADDHIST, 
       SXADDPAR, SXPAR(), READFITS(), WRITEFITS
 REVISION HISTORY:
       Written        W. Landsman         STX Co.    May, 1988
       Check for CCDGAIN, ATODGAIN keywords to get PHPADU  W. Landsman May 1997
       Fixed typo preventing compilation, groupsel parameter W.L. July 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Update for new FTINFO call    W. Landsman   May 2000

(See $IDLUTILS_DIR/goddard/pro/idlphot/t_nstar.pro)

T_SUBSTAR

 NAME:
       T_SUBSTAR
 PURPOSE:
       Driver procedure (for SUBSTAR) to subtract scaled PSF values 
 EXPLANATION:
       Computes residuals of the PSF fitting program

 CALLING SEQUENCE:
       T_SUBSTAR, image, fitsfile, id,[ psfname, /VERBOSE, /NOPSF ]

 INPUT-OUTPUT:
       IMAGE -  On input, IMAGE is the original image array.  A scaled
               PSF will be subtracted from IMAGE at specified star positions.
               Make a copy of IMAGE before calling SUBSTAR, if you want to
               keep a copy of the unsubtracted image array
 INPUTS:
       FITSFILE  - scalar string giving the name of the disk FITS ASCII 
               produced as an output from T_NSTAR.   

 OPTIONAL INPUTS:
       ID -  Index vector indicating which stars are to be subtracted.  If
               omitted, (or set equal to -1), then stars will be subtracted 
               at all positions specified by the X and Y vectors.
               (IDL convention - zero-based subscripts)
       PSFNAME - Name of the FITS file containing the PSF residuals, as
               generated by GETPSF.  SUBSTAR will prompt for this parameter
               if not supplied.      
 OPTIONAL INPUT KEYWORD:
       /VERBOSE - If this keyword is set and non-zero, then the value of each
               star number will be displayed as it is processed.
       /NOPSF - if this keyword is set and non-zero, then all stars will be 
               be subtracted *except* those used to determine the PSF.
               An improved PSF can then be derived from the subtracted image.
               If NOPSF is supplied, then the ID parameter is ignored
 NOTES:
       T_SUBSTAR does not modify the input FITS table.

 PROCEDURES USED:
       FTGET(), FTINFO, READFITS(), REMOVE, SUBSTAR
 REVISION HISTORY:
       Written, R. Hill, ST Sys. Corp., 22 August 1991
       Added NOPSF keyword   W. Landsman        March, 1996
       Use FITS format for PSF resduals         July, 1997
       Converted to IDL V5.0   W. Landsman   September 1997
       Call FTINFO first to improve efficiency   W. Landsman  May 2000

(See $IDLUTILS_DIR/goddard/pro/idlphot/t_substar.pro)

UNDEFINE

 NAME:
       UNDEFINE

 PURPOSE:
       The purpose of this program is to delete or undefine
       an IDL program variable from within an IDL program or
       at the IDL command line. It is a more powerful DELVAR.
       Pointer and structure variables are traversed recursively
       to undefine any variables pointed to in the pointer or in
       a structure dereference.

 AUTHOR:
       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1642 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:
       Utilities.

 CALLING SEQUENCE:
       UNDEFINE, variable

 REQUIRED INPUTS:
       variable: The variable to be deleted. Up to 10 variables may be specified as arguments.

 SIDE EFFECTS:
       The variable no longer exists.

 EXAMPLE:
       To delete the variable "info", type:

        IDL> Undefine, info
        
        IDL> var = ptr_new({a:ptr_New(5), b:findgen(11), c: {d:ptr_New(10), f:findgen(11)}})
        IDL> Help, /Heap
        Heap Variables:
            # Pointer: 3
            # Object : 0
        <PtrHeapVar3>   LONG      =            5
        <PtrHeapVar4>   LONG      =            10
        <PtrHeapVar5>   STRUCT    = -> <Anonymous> Array[1]
         
        IDL> Undefine, var
        IDL> Help, /Heap
        Heap Variables:
            # Pointer: 0
            # Object : 0
        IDL> Help, var
         VAR               UNDEFINED = <Undefined>

 MODIFICATION HISTORY:
       Written by David W. Fanning, 8 June 97, from an original program
       given to me by Andrew Cool, DSTO, Adelaide, Australia.
       Simplified program so you can pass it an undefined variable. :-) 17 May 2000. DWF
       Simplified it even more by removing the unnecessary SIZE function. 28 June 2002. DWF.
       Added capability to delete up to 10 variables at suggestion of Craig Markwardt. 10 Jan 2008. DWF.
       If the variable is a pointer, object or structure reference the variable is recursively traversed
          to free up all variables pointed to before the variable is itself destroyed. 10 June 2009. DWF.
       Updated to allow undefining of pointer arrays. 8 October 2009. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/undefine.pro)

UNZOOM_XY

 NAME:
      UNZOOM_XY
 PURPOSE:
      Converts X, Y position on the image display to the the X,Y position 
      on the corresponding image array.  (These  positions are identical 
      only for an unroamed, unzoomed image with with pixel (0,0) of the 
      image placed at position (0,0) on the TV.)

 CALLING SEQUENCE:
      UNZoom_XY, Xtv,Ytv,Xim,Yim, [ OFFSET =, ZOOM = ]   

 INPUTS:
      XTV - Scalar or vector giving X position(s) as read on the image
            display (e.g. with CURSOR,XTV,YTV,/DEVICE)
      XTV - Scalar or vector giving Y position(s) on the image display.
      If only 2 parameters are supplied then XTV and YTV will be modfied
      on output to contain the image array coordinates.

 OPTIONAL KEYWORD INPUT:
      OFFSET - 2 element vector giving the location of the image pixel (0,0) 
               on the window display.   OFFSET can be positive (e.g if the 
               image is centered in a larger window) or negative (e.g. if the
               only the central region of an image much larger than the window
               is being displayed. 
               Default value is [0,0], or no offset.
 OUTPUTS:
      XIM,YIM - X and Y coordinates of the image corresponding to the
            cursor position on the TV display.
 COMMON BLOCKS:
       If present, ZOOM_XY will use the TV and IMAGE common blocks which are
       defined in the MOUSSE software system (see 
        http://archive.stsci.edu/uit/analysis.html)   If the user is not using
       the MOUSSE software (which keeps track of the offset and zoom in each
       window) then the common blocks are ignored.
 NOTES:
       The integer value of a pixel is assumed to refer to the *center*
       of a pixel.
 REVISON HISTORY:
       Adapted from MOUSSE procedure  W. Landsman       March 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Proper handling of offset option          S. Ott/W. Landsman May 2000
       Put back common blocks for MOUSSE compatibility    September 2004

(See $IDLUTILS_DIR/goddard/pro/tv/unzoom_xy.pro)

UPDATE_DISTORT

 NAME:
    UPDATE_DISTORT
 PURPOSE:
    Update SIP nonlinear distortion coefficients for a linear transformation
 EXPLANATION:
    The SIP coefficients can account for nonlinearities in the astrometry
    of an astronomical image.    When the image is compressed or expanded
    these coefficients must be adjusted in a nonlinear way.
 CALLING SEQUENCE:
    UPDATE_DISTORT, distort, xcoeff, ycoeff
 INPUT/OUTPUT:
    distort - structure giving SIP coefficients.    See extast.pro for 
             description of the SIP distortion structure
    xcoeff - 2 element numeric vector describing the linear transformation
              xp = xcoeff[0]*x + xcoeff[1]
    xcoeff - 2 element numeric vector describing the linear transformation
              yp = ycoeff[0]*x + ycoeff[1]

 METHOD:
     The procedure TRANSFORM_COEFF is  used to determine how the
     coefficients change under the linear transformation.

     See example of usage in hrebin.pro
 REVISION HISTORY:
     Written, December 2007            W. Landsman

(See $IDLUTILS_DIR/goddard/pro/astrom/update_distort.pro)

UVBYBETA

 NAME:
       UVBYBETA
 PURPOSE:
       Derive dereddened colors, metallicity, and Teff from Stromgren colors.
 EXPLANATION:
       Adapted from FORTRAN routine of same name published by T.T. Moon, 
       Communications of University of London Observatory, No. 78. Parameters 
       can either be input interactively (with /PROMPT keyword) or supplied 
       directly.   

 CALLING SEQUENCE:
       uvbybeta, /PROMPT               ;Prompt for all parameters
       uvbybeta,by,m1,c1,Hbeta,n        ;Supply inputs, print outputs
       uvbybeta, by, m1, c1, Hbeta, n, Te, Mv, Eby, delm0, radius, 
                       [ TEXTOUT=, Eby_in =, Name =  ]

 INPUTS:
       by - Stromgren b-y color, scalar or vector
       m1 - Stromgren line-blanketing parameter, scalar or vector
       c1 - Stromgren Balmer discontinuity parameter, scalar or vector
       Hbeta - H-beta line strength index.  Set  Hbeta to 0 if it is not 
            known, and UVBYBETA will estimate a value based on by, m1,and c1.
            Hbeta is not used for stars in group 8.
       n -  Integer (1-8), scalar or vector,  giving approximate stellar 
            classification

       (1) B0 - A0, classes III - V, 2.59 < Hbeta < 2.88,-0.20 <   c0  < 1.00
       (2) B0 - A0, class   Ia     , 2.52 < Hbeta < 2.59,-0.15 <   c0  < 0.40
       (3) B0 - A0, class   Ib     , 2.56 < Hbeta < 2.61,-0.10 <   c0  < 0.50
       (4) B0 - A0, class   II     , 2.58 < Hbeta < 2.63,-0.10 <   c0  < 0.10
       (5) A0 - A3, classes III - V, 2.87 < Hbeta < 2.93,-0.01 < (b-y)o< 0.06
       (6) A3 - F0, classes III - V, 2.72 < Hbeta < 2.88, 0.05 < (b-y)o< 0.22
       (7) F1 - G2, classes III - V, 2.60 < Hbeta < 2.72, 0.22 < (b-y)o< 0.39
       (8) G2 - M2, classes  IV _ V, 0.20 < m0   < 0.76, 0.39 < (b-y)o< 1.00


 OPTIONAL INPUT KEYWORD:
       Eby_in - numeric scalar specifying E(b-y) color to use.   If not
             supplied, then E(b-y) will be estimated from the Stromgren colors
       NAME - scalar or vector string giving name(s) of star(s).  Used only 
               when writing to  disk for identification purposes.
       /PROMPT - if set, then uvbybeta.pro will prompt for Stromgren indicies
                interactively
       TEXTOUT  -  Used to determine output device.  If not present, the
               value of the !TEXTOUT system variable is used (see TEXTOPEN)
               textout=1       Terminal with /MORE (if a tty)
               textout=2       Terminal without /MORE
               textout=3       uvbybeta.prt   (output file)
               textout=4       Laser Printer 
               textout=5       User must open file         
               textout=7       Append to existing uvbybeta.prt file
               textout = filename (default extension of .prt)
      /PRINT - if set, then force display output information to the device 
               specified by !TEXTOUT.    By default, UVBYBETA does not display
               information if output variables are supplied (and TEXTOUT is
               not set). 

 OPTIONAL OUTPUTS:
       Te - approximate effective temperature
       MV - absolute visible magnitude
       Eby - Color excess E(b-y)
       delm0 - metallicity index, delta m0, (may not be calculable for early
               B stars).
       radius - Stellar radius (R/R(solar))
 EXAMPLE:
       Suppose 5 stars have the following Stromgren parameters

       by = [-0.001 ,0.403, 0.244, 0.216, 0.394 ]
       m1 = [0.105, -0.074, -0.053, 0.167, 0.186 ]
       c1 = [0.647, 0.215, 0.051, 0.785, 0.362] 
       hbeta = [2.75, 2.552, 2.568, 2.743, 0 ]
       nn = [1,2,3,7,8]              ;Processing group number

       Determine stellar parameters and write to a file uvbybeta.prt
       IDL> uvbybeta, by,m1,c1,hbeta, nn, t=3
            ==> E(b-y) = 0.050    0.414   0.283  0.023  -0.025
                Teff =   13060    14030   18420  7250    5760
                M_V =    -0.27    -6.91   -5.94  2.23    3.94
                radius=  2.71     73.51    39.84 2.02    1.53
 SYSTEM VARIABLES:
       The non-standard system variables !TEXTOUT and !TEXTUNIT will be  
       automatically defined if they are not already present.   

       DEFSYSV,'!TEXTOUT',1
       DEFSYSV,'!TEXTUNIT',0

 NOTES:
       (1) **This procedure underwent a major revision in January 2002
       and the new calling sequence may not be compatible with the old** (NAME
       is now a keyword rather than a parameter.)

       (2) Napiwotzki et al. (1993, A&A, 268, 653) have written a FORTRAN
           program that updates some of the Moon (1985) calibrations.  These
           updates are *not* included in this IDL procedure.
 PROCEDURES USED:
       DEREDD, TEXTOPEN, TEXTCLOSE
 REVISION HISTORY:                                           
       W. Landsman          IDL coding              February, 1988
       Keyword textout added, J. Isensee, July, 1990
       Made some constants floating point.   W. Landsman    April, 1994
       Converted to IDL V5.0   W. Landsman   September 1997
       Added Eby_in, /PROMPT keywords, make NAME a keyword and not a parameter
                 W. Landsman      January 2002

(See $IDLUTILS_DIR/goddard/pro/astro/uvbybeta.pro)

VACTOAIR

 NAME:
	VACTOAIR
 PURPOSE:
	Convert vacuum wavelengths to air wavelengths
 EXPLANATION:
	Corrects for the index of refraction of air under standard conditions.  
	Wavelength values below 2000 A will not be altered.  Accurate to 
	about 10 m/s.

 CALLING SEQUENCE:
	VACTOAIR, WAVE_VAC, [WAVE_AIR]

 INPUT/OUTPUT:
	WAVE_VAC - Vacuum Wavelength in Angstroms, scalar or vector
		If the second parameter is not supplied, then this will be
               updated on output to contain double precision air wavelengths.

 OPTIONAL OUTPUT:
        WAVE_AIR - Air wavelength in Angstroms, same number of elements as
                 WAVE_VAC, double precision

 EXAMPLE:
	If the vacuum wavelength is  W = 2000, then 

	IDL> VACTOAIR, W 

	yields an air wavelength of W = 1999.353 Angstroms

 METHOD:
	Formula from Ciddor 1996  Applied Optics , 35, 1566

 REVISION HISTORY
	Written, D. Lindler 1982 
	Documentation W. Landsman  Feb. 1989
       Use Ciddor (1996) formula for better accuracy in the infrared 
           Added optional output vector, W Landsman Mar 2011

(See $IDLUTILS_DIR/goddard/pro/astro/vactoair.pro)

VALID_NUM()

 NAME: 
     VALID_NUM()
 PURPOSE:               
     Check if a string is a valid number representation.
 EXPLANATION:              
     The input string is parsed for characters that may possibly
     form a valid number.  It is more robust than simply checking
     for an IDL conversion error because that allows strings such
     as '22.3qwert' to be returned as the valid number 22.3

     This function had a major rewrite in August 2008 to use STREGEX
     and allow vector input.    It should be backwards compatible.
 CALLING SEQUENCE: 
     IDL> status = valid_num(string  [,value]  [,/integer])
    
 INPUTS:
     string  -  the string to be tested, scalar or array
               
 RETURNS
     status - byte scalar or array, same size as the input string
              set to 1 where the string is a  valid number, 0 for invalid
 OPTIONAL OUTPUT:               
     value     - The value the string decodes to, same size as input string.
           This will be returned as a double precision number unless 
           /INTEGER is present, in which case a long integer is returned.
           
 OPTIONAL INPUT KEYWORD:          
    /INTEGER   -  if present code checks specifically for an integer.
 EXAMPLES:
     (1) IDL> print,valid_num(3.2,/integer) 
        --> 0     ;Since 3.2 is not an integer 
     (2) IDL> str =['-0.03','2.3g', '3.2e12']
         IDL> test = valid_num(str,val)
              test = [1,0,1]    &  val =  [-0.030000000 ,NaN ,3.2000000e+12]
 REVISION HISTORY:
          Version 1, C D Pike, RAL, 24-May-93
          Version 2, William Thompson, GSFC, 14 October 1994
                       Added optional output parameter VALUE to allow
                       VALID_NUM to replace STRNUMBER in FITS routines.
          Version 3 Wayne Landsman rewrite to use STREGEX, vectorize
          Version 4 W.L. (fix from C. Markwardt) Better Stregex expression, 
                    was missing numbers like '134.' before Jan 1 2010

(See $IDLUTILS_DIR/goddard/pro/misc/valid_num.pro)

VECT

 NAME:
	VECT
 PURPOSE:
	Print a set of numbers as a string with delimiters included
 EXPLANATION:
	This function returns the given vector in parenthesized coordinates
	as in the form (X,Y).  No limit on the number of dimensions.  Also
	note that the vector does not need to be numbers.  It may also be a
	string vector.  e.g. ['X','Y']

 CALLING SEQEUNCE:
	tmp = VECT( vctr, [ form, FORMAT = , DELIM =  ] )
 INPUT:
	VCTR      The vector to be displayed  e.g. [56,44]

 OPTIONAL KEYWORD INPUT:
	FORMAT    This KEYWORD allows the specification of a format for the
		elements.  e.g.: VECT([2,3],format='(f7.1)') gives '(2.0,3.0)'
	DELIM     This KEYWORD specifies the delimeter.  The default is ',' but
		other useful examples might be ', ' or ':'

 OPTIONAL INPUT
	FORM      This parameter may be used instead of the keyword FORMAT

 OUTPUT:
	tmp       A returned string of the parenthesized vector

 Other Procedures/Functions Called:
	STRN

 HISTORY:
	03-JUL-90 Version 1 written by Eric W. Deutsch
	24-AUG-91 Format='' keyword added (E. Deutsch)
	29-AUG-91 FORM parameter added (E. Deutsch)
	Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/vect.pro)

VSYM

 NAME:
       VSYM

 PURPOSE:
       Create "Mongo"-like polygonal plot symbols
 EXPLANATION:
       This procedure generates a subset of Mongo-like plot symbols.
       The symbols are the rotationally symmetric ones that have
       a specified number of vertices and are either open or filled.
       (The half-filled symbols are not included.)     After defining the
       plot symbol with VSYM, make the call to PLOT (or PLOTS or OPLOT) with 
       PSYM=8.

 CATEGORY:
       Graphics

 CALLING SEQUENCE:
       VSYM, Nvert

 INPUT POSITIONAL PARAMETERS:
       Nvert:     Number of vertices in plot symbol.  Maximum value
                  used is 24.

 INPUT KEYWORD PARAMETERS:
       STAR:      Set this flag to get a star.  E.g., 
                  vsym, 5,/star gets you a pentagram.
       SKELETON:  Set this flag to get an asterisk-like symbol, where
                  the center is connected to each vertex.  E.g.,
                  vsym, 4, /skel gets you an X.
       POLYGON:   Set this flag to get a regular polygon.  This is
                  the default symbol type.
       FILL:      Set this flag to get filled symbol.  Default=open
       ROT:       Rotation of symbol about center, in degrees.
                  E.g., vsym, 4, rot=45 gets you a diamond, whereas
                  vsym, 4 gets you a square.
       THICK:     Line thickness of symbol.  Default=!P.thick

 MODIFICATION HISTORY:
       Written by:     R. S. Hill, RITSS, 2 Oct 98

(See $IDLUTILS_DIR/goddard/pro/plot/vsym.pro)

WCSSPH2XY

 NAME:
     WCSSPH2XY
 PURPOSE:
     Convert spherical coordinates to x and y (map) angular coordinates
 EXPLANATION:
     Convert spherical (longitude and latitude -- sky) coordinates to x
     and y (map) angular coordinates.  This procedure is the inverse of
     WCSXY2SPH.    See WCS_DEMO for example of use.

     This is a lower level procedure -- given a FITS header, the user will
     usually use ADXY which will then call WCSSPH2XY with the appropriate
     parameters.
 CATEGORY:
     Mapping and Auxiliary FITS Routine

 CALLING SEQUENCE:
      wcssph2xy, longitude, latitude, x, y, [ map_type , CTYPE = ,
               FACE =,PV2= , CRVAL = , CRXY = , LONGPOLE = ,
               LATPOLE = , NORTH_OFFSET =, SOUTH_OFFSET =, BADINDEX =]

 INPUT PARAMETERS:
     longitude - longitude of data, scalar or vector, in degrees
     latitude - latitude of data, same number of elements as longitude,
               in degrees
     map_type - optional positional parameter, numeric scalar (0-26)
               corresponding to a particular map projection.  This is not a
               FITS standard, it is simply put in to allow function similar
               to that of less general map projection procedures (eg AITOFF).
               The following list gives the map projection types and their
               respective numbers.

  FITS  Number  Name                       Comments
  code   code
  ----  ------  -----------------------    -----------------------------------
   DEF     0    Default = Cartesian
   AZP     1    Zenithal perspective       PV2_1 required
   TAN     2    Gnomic                     AZP w/ mu = 0
   SIN     3    Orthographic               PV2_1,PV2_2 optional
   STG     4    Stereographic              AZP w/ mu = 1
   ARC     5    Zenithal Equidistant
   ZPN     6    Zenithal polynomial        PV2_0, PV2_1....PV2_20 possible
   ZEA     7    Zenithal equal area
   AIR     8    Airy                       PV2_1 required
   CYP     9    Cylindrical perspective    PV2_1 and PV2_2 required
   CAR    10    Cartesian
   MER    11    Mercator
   CEA    12    Cylindrical equal area     PV2_1 required
   COP    13    Conical perspective        PV2_1 and PV2_2 required
   COD    14    Conical equidistant        PV2_1 and PV2_2 required
   COE    15    Conical equal area         PV2_1 and PV2_2 required
   COO    16    Conical orthomorphic       PV2_1 and PV2_2 required
   BON    17    Bonne's equal area         PV2_1 required
   PCO    18    Polyconic
   SFL    19    Sanson-Flamsteed
   PAR    20    Parabolic
   AIT    21    Hammer-Aitoff
   MOL    22    Mollweide
   CSC    23    Cobe Quadrilateralized     convergence of inverse is poor
                Spherical Cube
   QSC    24    Quadrilateralized
                Spherical Cube
   TSC    25    Tangential Spherical Cube
   SZP    26    Slant Zenithal Projection   PV2_1,PV2_2, PV2_3 optional
   HPX    27    HealPix
   HCT    28    HealCart (Cartesian approximation of Healpix)

 OPTIONAL INPUT KEYWORD PARAMETERS:

     CTYPE - One, two, or three element vector containing 8 character
              strings corresponding to the CTYPE1, CTYPE2, and CTYPE3
              FITS keywords:

               CTYPE[0] - first four characters specify standard system
               ('RA--','GLON' or 'ELON' for right ascension, Galactic
               longitude or ecliptic longitude respectively), second four
               letters specify the type of map projection (eg '-AIT' for
               Aitoff projection)
               CTYPE[1] - first four characters specify standard system
               ('DEC-','GLAT' or 'ELAT' for declination, galactic latitude
               or ecliptic latitude respectively; these must match
               the appropriate system of ctype1), second four letters of
               ctype2 must match second four letters of ctype1.
               CTYPE[2] - if present must be the 8 character string,'CUBEFACE',
                only used for spherical cube projections to identify an axis
               as containing the face on which each x and y pair of
               coordinates lie.
       PV2  - Vector of projection parameter associated with latitude axis
             PV2 will have up to 21 elements for the ZPN projection, up to 3
             for the SIN projection and no more than 2 for any other
             projection.   The first element corresponds to PV2_1, the
             second to PV2_2, etc.
       CRVAL - 2 element vector containing standard system coordinates (the
               longitude and latitude) of the reference point
       CRXY - 2 element vector giving the x and y coordinates of the
               reference point, if this is not set the offset is [0,0]
               This is not a FITS standard -- it is similar to CRPIX but in
               angular X,Y coordinates (degrees) rather than pixel coordinates
       LATPOLE -  native latitude of the standard system's North Pole
       LONGPOLE - native longitude of standard system's North Pole, default
               is 180 degrees for Zenithal systems
       NORTH_OFFSET - offset (radians) added to input points near north pole.
       SOUTH_OFFSET - offset (radians) added to input points near south pole.
       BADINDEX     - vector, list of transformed points too close to poles.


 OUTPUT PARAMETERS:

       x - x coordinate of data, same number of elements as longitude, in
               degrees; if CRXY is set, then x will be returned offset by
               crxy(0).  NOTE: x in all map projections increases to the
               left, not the right.
       y - y coordinate of data, same number of elements as longitude, in
               degrees; if CRXY is set, y will be returned offset by crxy[1]
       bad - vector returning index to transformed points close to pole.

 OPTIONAL OUTPUT KEYWORD PARAMETERS:
       FACE - a output variable used for spherical cube projections to
               designate the face of the cube on which the x and y
               coordinates lie.   Will contain the same number of elements as
               X and Y.    Must contain at least 1 arbitrary element on input
               If FACE is NOT defined on input, it is assumed that the
               spherical cube projection is laid out over the whole sky
               in the "sideways T" configuration.
 NOTES:
       The conventions followed here are described in more detail in
       "Representations of Celestial Coordinates in FITS" by Calabretta
       and  Greisen (2002, A&A, 395, 1077; also see
       http://fits.gsfc.nasa.gov/fits_wcs.html).  The general
       scheme outlined in that article is to first use WCS_ROTATE to convert
       coordinates in one of three standard systems (celestial, galactic,
       or ecliptic) into a "native system" of latitude and longitude.  The
       latitude and longitude are then converted into x and y coordinates
       which depend on the map projection which is performed.   The rotation
       from standard to native coordinates can be skipped if one so desires.
       This procedure necessitates two basic sections.  The first converts
       "standard" coordinates to "native" coordinates while the second converts
       "native" coordinates to x and y coordinates.  The first section is
       simply a call to WCS_ROTATE, while the second contains the guts of
       the code in which all of the map projection is done.  This procedure
       can be called in a form similar to AITOFF, EQPOLE, or QDCB by calling
       wcssph2xy with a fifth parameter specifying the map projection by
       number and by not using any of the keywords related to the map
       projection type (e.g. CTYPE).

 PROCEDURE:

       The first task of the procedure is to do general error-checking to
       make sure the procedure was called correctly and none of the
       parameters or keywords conflict.  This is particularly important
       because the procedure can be called in two ways (either using
       FITS-type keywords or using a number corresponding to a map projection
       type).  All variables are converted into double precision values and
       angular measurements are converted from degrees into radians.
       If necessary, longitude values are converted into the range -pi to pi.
       Any latitude points close to the  of the poles are mapped to a specific
       latitude of  from the pole so that the map transformations become
       completely invertible.  The magnitude of this correction is given by
       the keywords NORTH_OFFSET and SOUTH_OFFSET and a list of affected
       points is optionally returned in the "badindex" output parameter.
       The next task of the procedure is to convert the "standard"
       coordinates to "native" coordinates by rotating the coordinate system.
       This rotation is performed by the procedure WCS_ROTATE and is governed
       by the keywords CRVAL and LONGPOLE.   The final task of the WCSSPH2XY
       is to take "native" latitude and longitude coordinates and convert
       them into x and y coordinates.  Any map specific error-checking is
       done at this time.  All of the equations were obtained from
       "Representations of Celestial Coordinates in FITS" and cases needing
       special attention are handled appropriately (see the comments with
       individual map projections for more information on special cases).

       Note that a further transformation (using the CD matrix) is required
       to convert the (x,y) coordinates to pixel coordinates.
 COMMON BLOCKS:

       none

 PROCEDURES CALLED:
       WCS_ROTATE


 AUTHOR:

       Rick Balsano

 MODIFICATIONS/REVISION LEVEL:

       1.1     8/31/93
       2.3     9/15/93  W. Landsman (HSTX) Update quad cube coords, vectorize
                        keywords
       2.4     12/29/93 I. Freedman (HSTX) Eliminated LU decomposition
       2.5     1/5/93   I. Freedman (HSTX) Offset keywords / bad point index
       2.6     Dec 94   Compute pole for transformations where the reference
                       pixel is at the native origin    W. Landsman (HSTX)
       2.7     May 95  Change internal variable BETA for V4.0 compatibility
       2.8     June 95 Change loop indices from integer to long
       2.9     3/18/96 Change FACE usage for cube projections to match WCSLIB
                       C/FORTRAN software library.
       2.10    02/18/99 Fixed implementation of ARC algorithm
       2.11    June 2003 Update conic projections, add LATPOLE keyword
	2.12	Aug 2003, N.Rich - Fix pre-V5.5 bug from previous update
       2.13    Sep 2003, W. Landsman CTYPE keywords need not be 8 characters
       2.14    Jan 2004, W. Landsman don't modify scalars, fix PARabolic code
       2.15    Feb 2004, W. Landsman Fix AZP and AIR algorithms
       3.0    May 2004  W. Landsman Support extended SIN (=NCP), slant zenithal
                  (SZP), and zenithal polynomail (ZPN) projections, use
                   PV2 keyword vector instead of PROJP1, PROJP2
       3.1     Jul 2005 W.Landsman/C. Markwardt Set unprojectable points in
                   tangent projection to NaN
       3.1.1   Jul 2005 Fixed 3.1 mod to work for scalars
       3.2     Dec 2005 Fixed Airy projection for latitude centered at 90 deg
       3.3     Aug 2007 R. Munoz, W.Landsman Correct treatment of PV1_2 and
                        PV2_2 parameters
       3.4    Oct 2007  Sergey Koposov Support HEALPIX projection
       3.4.1  June 2009 Check for range of validity of ZPN polynomial W.L.
       3.5    May 2012  Benjamin Alan Weaver, Add nonstandard HEALCART 
                        projection, Allow map_index to be > 25

(See $IDLUTILS_DIR/goddard/pro/astrom/wcssph2xy.pro)

WCSXY2SPH

 NAME:
      WCSXY2SPH

 PURPOSE:
      Convert x and y (map) coordinates to spherical coordinates
 EXPLANATION:
      To convert x and y (map) coordinates to spherical (longitude and
      latitude or sky) coordinates.    This procedure is the inverse of
      WCSSPH2XY.

     This is a lower level procedure -- given a FITS header, the user will
     usually use XYAD which will then call WCSXY2SPH with the appropriate
     parameters.
 CATEGORY:
      Mapping and Auxilary FITS Routine

 CALLING SEQUENCE:

      wcsxy2sph, x, y, longitude, latitude, [map_type], [ CTYPE = ,$
             FACE = ,PV2 = ,CRVAL =, CRXY =, LONGPOLE=, LATPOLE=]

 INPUT PARAMETERS:

       x - x coordinate of data, scalar or vector, in degrees, NOTE: x
               increases to the left, not the right
       y - y coordinate of data, same number of elements as x, in degrees
       map_type - optional positional parameter, scalar corresponding to a
               particular map projection.  This is not a FITS standard, it is
               simply put in to allow function similar to that of less general
               map projection procedures (eg AITOFF).  The following list gives
               the map projection types and their respective numbers.

  FITS  Number  Name                       Comments
  code   code
  ----  ------  -----------------------    -----------------------------------
   DEF     0    Default = Cartesian
   AZP     1    Zenithal perspective       pv2_1 required
   TAN     2    Gnomic                     AZP w/ pv2_1 = 0
   SIN     3    Orthographic               pv2_1, pv2_2 optional
   STG     4    Stereographic              AZP w/ pv2_1 = 1
   ARC     5    Zenithal Equidistant
   ZPN     6    Zenithal polynomial        PV2_0, PV2_1....PV2_20 possible
   ZEA     7    Zenithal equal area
   AIR     8    Airy                       pv2_1 required
   CYP     9    Cylindrical perspective    pv2_1 and pv2_2 required
   CAR    10    Cartesian
   MER    11    Mercator
   CEA    12    Cylindrical equal area     pv2_1 required
   COP    13    Conical perspective        pv2_1 and pv2_2 required
   COD    14    Conical equidistant        pv2_1 and pv2_2 required
   COE    15    Conical equal area         pv2_1 and pv2_2 required
   COO    16    Conical orthomorphic       pv2_1 and pv2_2 required
   BON    17    Bonne's equal area         pv2_1 required
   PCO    18    Polyconic
   SFL    19    Sanson-Flamsteed
   PAR    20    Parabolic
   AIT    21    Hammer-Aitoff
   MOL    22    Mollweide
   CSC    23    Cobe Quadrilateralized     inverse converges poorly
                Spherical Cube
   QCS    24    Quadrilateralized
                Spherical Cube
   TSC    25    Tangential Spherical Cube
   SZP    26    Slant Zenithal perspective  PV2_1,PV2_2, PV2_3 optional
   HPX    27    HealPix
   HCT    28    HealCart (Cartesian approximation of Healpix)

 OPTIONAL KEYWORD PARAMETERS:

       CTYPE - One, two, or three element vector containing 8 character
               strings corresponding to the CTYPE1, CTYPE2, and CTYPE3
               FITS keywords:

               CTYPE[0] - first four characters specify standard system
               ('RA--','GLON' or 'ELON' for right ascension, galactic
               longitude or ecliptic longitude respectively), second four
               letters specify the type of map projection (eg '-AIT' for
               Aitoff projection)
               CTYPE[1] - first four characters specify standard system
               ('DEC-','GLAT' or 'ELAT' for declination, galactic latitude
               or ecliptic latitude respectively; these must match
               the appropriate system of ctype1), second four letters of
               ctype2 must match second four letters of ctype1.
               CTYPE[2] - if present must be the 8 character string,'CUBEFACE',
                only used for spherical cube projections to identify an axis
               as containing the face on which each x and y pair of
               coordinates lie.
       FACE - a input variable used for spherical cube projections to
               designate the face of the cube on which the x and y
               coordinates lie.   Must contain the same number of elements
               as X and Y.
       CRVAL - 2 element vector containing standard system coordinates (the
               longitude and latitude) of the reference point
       CRXY - 2 element vector giving the x and y coordinates of the
               reference point, if this is not set the offset of the x
               coordinate is assumed to be 0.
       LATPOLE -  native latitude of the standard system's North Pole
       LONGPOLE - native longitude of standard system's North Pole, default
               is 180 degrees, numeric scalar
       PV2  - Vector of projection parameter associated with latitude axis
             PV2 will have up to 21 elements for the ZPN projection, up to 3
             for the SIN projection and no more than 2 for any other
             projection.   The first element corresponds to PV2_1, the
             second to PV2_2, etc.

 OUTPUT PARAMETERS:

       longitude - longitude of data, same number of elements as x, in degrees
       latitude - latitude of data, same number of elements as x, in degrees

       Longitude and latitude will be set to NaN, wherever elements of X,Y
       have no corresponding longitude, latitude values.
 NOTES:
       The conventions followed here are described in more detail in the paper
      "Representations of Celestial Coordinates in FITS" by Calabretta &
       Greisen (2002, A&A, 395, 1077, also see
       http://fits.gsfc.nasa.gov/fits_wcs.html).   The general scheme
       outlined in that article is to convert x and y coordinates into a
       "native" longitude and latitude and then rotate the system into one of
       three generally recognized systems (celestial, galactic or ecliptic).

       This procedure necessitates two basic sections.  The first converts
       x and y coordinates to "native" coordinates while the second converts
       "native" to "standard" coordinates.  The first section contains the
       guts of the code in which all of the map projection is done.  The
       second step is performed by WCS_ROTATE and only involves rotation of
       coordinate systems.  WCSXY2SPH can be called in a form similar to
       AITOFF, EQPOLE, or QDCB by calling wcsxy2sph with a fifth parameter
       specifying the map projection by number and by not using any of the
       keywords related to the map projection type (eg ctype1 and ctyp2).

 PROCEDURE:
       The first task of the procedure is to do general error-checking to
       make sure the procedure was called correctly and none of the
       parameters or keywords conflict.  This is particularly important
       because the procedure can be called in two ways (either using
       FITS-type keywords or using a number corresponding a map projection
       type).  All variables are converted into double precision values.

       The second task of the procedure is to take x and y coordinates and
       convert them into "native" latitude and longitude coordinates.
       Map-specific error-checking is done at this time.  All of the
       equations were obtained from "Representations of Celestial
       Coordinates in FITS" and cases needing special attention are handled
       appropriately (see the comments with individual map projections for
       more information on special cases).     WCS_ROTATE is then called to
       convert the "native" coordinates to "standard" coordinates by rotating
       the coordinate system.  This rotation is governed by the keywords
       CRVAL, and LONGPOLE.  The transformation is a straightforward
       application of euler angles.  Finally, longitude values are converted
       into the range from 0 to 360 degrees.

 COMMON BLOCKS:
       none
 PROCEDURES CALLED:
       WCS_ROTATE

 AUTHOR:

       Rick Balsano

 MODIFICATIONS/REVISION LEVEL:

 1.1    8/31/93
 1.2    9/12/93   W. Landsman Vectorized CRXY, CRVAL, CTYPE
 1.3    29/12/93  I. Freedman Eliminated LU decomposition
 1.4    22/09/94  W. Landsman If scalar input, then scalar output
 1.5    02/03/05  W. Landsman Change variable name BETA for V4.0 compatibility
 1.6    06/07/05  W. Landsman Change loop index from integer to long
 1.7    02/18/99  W. Landsman Fixed implementation of ARC algorithm
 1.8    June 2003 W. Landsman Update conic projections, add LATPOLE keyword
 1.81   Sep 2003 W. Landsman Avoid divide by zero
 1.82   Sep 2003 W. Landsman CTYPE keywords need not be 8 characters
 1.83   Sep 2003 W. Landsman Preserve input array sizes
 1.9    Jan 2004 W. Landsman don't modify scalars, fix PARabolic code
 2.0    Feb 2004 W. Landsman Fix AIR and AZP projections
 2.1    Feb 2004 W. Landsman Fix tangent projection for matrix input
 3.0    May 2004  W. Landsman Support extended SIN (=NCP), slant zenithal
                  (SZP), and zenithal polynomial (ZPN) projections, use
                   PV2 keyword vector instead of PROJP1, PROJP2
 3.1    May 2004 W. Landsman/J. Ballet Handle NaN values, flag invalid output
                   for AITOFF projection
 3.1.1  Dec 2005 W. Landsman/W. Thompson Fixed problem with Airy projection
                   centered on 90 degree latitude
 3.1.2  May 2006 W. Landsman/Y.Sato Fix problem selecting the correct root
                    for the ZPN projection
 3.2    Aug 2007  W. Landsman Correct treatment of PVi_j parameters
 3.3    Oct 2007  Sergey Koposov Support HEALPIX projection
 3.4    May 2012  Benjamin Alan Weaver, Add nonstandard HEALCART 
                        projection, Allow map_index to be > 25

(See $IDLUTILS_DIR/goddard/pro/astrom/wcsxy2sph.pro)

WCS_DEMO

 NAME:
       WCS_DEMO

 PURPOSE:
       Demonstrate the basic capabilities of procedures WCSSPH2XY & WCSXY2SPH

 CATEGORY:
       Mapping and Auxilary FITS Demo Routine

 CALLING SEQUENCE:

       .run wcs_demo: compiles wcs_demo and the supporting demo routines
       wcs_demo: run the demo

 INPUT PARAMETERS:

       none

 OUTPUT PARAMETERS:
       none

 PROCEDURE:

       This is a demo program which is meant to call the routines 
       wcssph2xy.pro and wcsxy2sph.pro.  Since the purpose of this
       routine is both to show what the routines can do and what the
       user has to do, a file is created with all of the commands 
       needed to complete the desired operation.  Wcs_demo actually 
       executes this command file, so the user can exactly duplicate
       the results by simply re-executing this file.  Also, this 
       allows a user to edit an already existing file which calls 
       wcssph2xy.pro and wcsxy2sph.pro properly and extend the file's
       usefulness.  This demo program allows several possible tests.
       The first option is to simply draw a grid of evenly spaced
       latitude and longitude lines in a particular map transformation.
       Another possibility is to do a full loop, creating a Cartesian
       grid of latitude and longitude lines and calling wcssph2xy.pro
       to convert them to a particular map.  Then, wcsxy2sph.pro is
       called to invert the process and the difference between the
       original and final latitudes and longitudes can be plotted.
       This allows one to assess the level of the numerical errors
       introduced by the mapping routines.  A third possible option is to
       look at some of the map transformations and include rotations of
       the reference points so that a different perspective is given.

 COMMON BLOCKS:
       none

 PROCEDURES CALLED:
       SPHDIST(), WCSXY2SPH, WCSSPH2XY
 COPYRIGHT NOTICE:

       Copyright 1991, The Regents of the University of California. This
       software was produced under U.S. Government contract (W-7405-ENG-36)
       by Los Alamos National Laboratory, which is operated by the
       University of California for the U.S. Department of Energy.
       The U.S. Government is licensed to use, reproduce, and distribute
       this software. Neither the Government nor the University makes
       any warranty, express or implied, or assumes any liability or
       responsibility for the use of this software.

 AUTHOR:

       Rick Balsano

 MODIFICATIONS/REVISION LEVEL:

       1.1     8/31/93
       1.2     3/19/96 - J. Bloch - LANL
                        - Made compatible with wcslib-2.2 by Calabretta.
       Converted to IDL V5.0   W. Landsman   September 1997
       Updated for conical projections W. Landsman  July 2003

(See $IDLUTILS_DIR/goddard/pro/astrom/wcs_demo.pro)

WCS_GETPOLE

 NAME:
       WCS_GETPOLE 

 PURPOSE:
       Compute the coordinates of the native pole for a non-polar projection
 EXPLANATION:
       For non-polar (cylindrical or conic) projections, the native pole is
       not at the reference point, and WCS_GETPOLE is used to determine the
       position of the native pole.    See section 2.4 of the paper 
       "Representation of Celestial Coordinates in FITS" by Calabretta 
       Greisen (2002, A&A, 395, 1077, also available at  
       http://fits.gsfc.nasa.gov/fits_wcs.html    Called by WCS_ROTATE

 CALLING SEQUENCE:
       WCS_GETPOLE,  crval, lonpole, theta0, alpha_p, delta_p, LATPOLE= ]

 INPUT PARAMETERS:
       crval - 2 element vector containing standard system coordinates (the 
               longitude and latitude) of the reference point in degrees
       lonpole - native longitude of the celestial North Pole (degrees)
       theta0 - native latitude of the fiducial point
 OUTPUT PARAMETERS:
       alpha_p, delta_p - celestial longitude and latitude of the native pole
               (Radians)
 OPTIONAL KEYWORD INPUT PARAMETERS:
       LATPOLE - native latitude of the celestial North Pole (degrees)
 REVISION HISTORY:
       Written    W. Landsman               June, 2003
       Fix calculation when theta0 is not 0 or 90     February 2004
       E. Hivon: alpha_p, delta_p consistenly in Radians May 2010

(See $IDLUTILS_DIR/goddard/pro/astrom/wcs_getpole.pro)

WCS_ROTATE

 NAME:
       WCS_ROTATE 

 PURPOSE:
       Rotate between standard (e.g. celestial) and native coordinates
 EXPLANATION:
       Computes a spherical coordinate rotation between native coordinates 
       and  standard celestial coordinate system (celestial, Galactic, or
       ecliptic).   Applies the equations in Appendix B of the paper 
       "Representation of Celestial Coordinates in FITS" by Calabretta 
       Greisen (2002, A&A, 395, 1077).    Also see 
       http://fits.gsfc.nasa.gov/fits_wcs.html

 CATEGORY:
       Mapping and Auxiliary FITS Routine

 CALLING SEQUENCE:
       WCS_ROTATE, longitude, latitude, phi, theta, crval, 
               [LONGPOLE = , LATPOLE = , /REVERSE, /ORIGIN ]

 INPUT PARAMETERS:
       crval - 2 element vector containing standard system coordinates (the 
               longitude and latitude) of the reference point

 INPUT OR OUTPUT PARAMETERS
       longitude - longitude of data, scalar or vector, in degrees, in the
               standard celestial coordinate system
       latitude - latitude of data, same number of elements as longitude, 
               in degrees
       phi - longitude of data in the native system, in degrees, scalar or
               vector
       theta - latitude of data in the native system, in degrees, scalar or
               vector

       If the keyword(REVERSE) is set then phi and theta are input parameters
       and longitude and latitude are computed.    Otherwise, longitude and
       latitude are input parameters and phi and theta are computed.

 OPTIONAL KEYWORD INPUT PARAMETERS:

      ORIGIN - If this keyword is set and non-zero, then the reference point
               given by CRVAL in the native system is assumed to be at the
               origin of the coordinates, rather than at the North Pole.
               ORIGIN should be set for cylindrical projections (Cylindrical
               perspective-CYP, Cartesian - CAR, Mercator - MER, Cylindrical
               Equal area - CEA) and conventional projections (Bonne's equal
               area - BON, Polyconic - PCO, Sinusoidal - GLS, Parabolic - PAR,
               Aitoff - AIT, Mollweide - MOL, COBE quadrilateralized sphere -
               CSC, Quadrilateralized Spherical Cube - QSC, and Tangential
               Spherical Cube - TSC)

       LONGPOLE - native longitude of standard system's North Pole, default
               for a Zenithal system is 180 degrees
       LATPOLE -  native latitude of the standard system's North Pole
       /REVERSE - if set then phi and theta are input parameters and longitude
                  and latitude are computed.    By default, longitude and
                  latitude are input parameters and phi and theta are computed.
 REVISION HISTORY:
       Written    W. Landsman               December, 1994
       Fixed error in finding North Pole if /ORIGIN and LONGPOLE NE 180
       Xiaoyi Wu and W. Landsman,   March, 1996
       Fixed implementation of March 96 error, J. Thieler,  April 1996
       Updated to IDL V5.0   W. Landsman    December 1997
       Fixed determination of alpha_p if /ORIGIN and LONGPOLE EQ 180
               W. Landsman    May 1998
       Ensure argument of ASIN() is -1<x<-1 after roundoff 
               W. Landsman/R. Arendt  June 2002
       Call WCS_GETPOLE, accept LATPOLE keyword, update cylindrical coords
               W. Landsman  June 2003 
       Don't attempt to rotate NaN values   W. Landsman  May 2004

(See $IDLUTILS_DIR/goddard/pro/astrom/wcs_rotate.pro)

WEBGET()

 NAME: 
    WEBGET()

 PURPOSE: 
    Use the IDL SOCKET procedure to get data from http servers

 EXPLANATION: 
     WEBGET() can access http servers - even from behind a firewall - 
     and perform simple downloads. Currently, text and FITS files can be 
     accessed.    

 CALLING SEQUENCE: 
      a=webget(URL)

 INPUTS: 
      URL - scalar string giving a fully qualified url of the form
          'http://server.eso.org/path/file.html'.    WEBGET() can
          also use other valid URLs that contain 'GET' or 'POST' codes.

 OPTIONAL INPUT KEYWORD PARAMETERS: 
       COPYFILE - if set to a valid filename (file must have write permission),
            the data contents of the web server's answer is copied to that 
            file.
       HTTP10 - If set, then use the HTTP 1.0 
       POST - if set to a structure, the structure tags and values
              will be used as post variables and POST'ed to the URL.
              If POST is not set, the normal HTTP GET is used to
              retrieve the URL.
       /SILENT - If set, the information error messages are suppressed
       TIMEOUT - Integer scalar giving number of seconds to wait to connect 
                or for data to arrive before giving up and issuing an error.
                Default=15 seconds 
 OUTPUTS: A structure with the following fields:

            .Header - the HTTP header sent by the server

            .Text   - The text part of the downloaded file. If the
                     content type of the file was not of class
                     'text',  this will be an empty string.

            .ImageHeader - Header file of a FITS-image. FITS images
                          are read when the content type is
                          'image/fits' or 'application/octet-stream'
                          (for dss-access). If the file is not a FITS
                          image,  this will be an empty string.

            .Image - The FITS image read from the server. If the file
                    did not contain a FITS image,  this will be zero.


 RESTRICTIONS: 
     The mime-type recognition is extremely limited. Only the content-type is 
     determined. Any text-file  will be stored in out.Text. The only other 
     category which can be fetched is FITS files,  which will be stored in 
     out.Image and out.ImageHeader.

     PROXY: If you are behind a firewall and have to access the net through a 
         Web proxy,  set the environment variable 'http_proxy' to point to 
         your proxy server and port, e.g. 
         'setenv http_proxy=http://web-proxy.mpia-hd.mpg.de:3128'

               The URL *MUST* begin with "http://".

 PROCEDURE: 
     Open a socket to the webserver and download the header. After deciding 
     whether it is text or binary, either store the text or try to read a 
     FITS file.

 EXAMPLE: 
      IDL> a=webget('http://www.mpia.de/index.html')
      IDL> print,a.Text
      or

          > PointingRA=0.0
          > PointingDE=30.0
          > QueryURL = strcompress("http://archive.eso.org/dss/dss/image?ra="+$
          >                          string(PointingRA)+$
          >                          "&dec="+$
          >                          string(PointingDE)+$
          >                          "&x=10&y=10&Sky-Survey=DSS1&mime-type=download-fits", $
          >                          /remove)
          > a=webget(QueryURL)
          > tvscl,a.Image
          > print,a.ImageHead


 MODIFICATION HISTORY: 
     Written by M. Feldt, Heidelberg, Oct 2001 <mfeldt@mpia.de>
     Use /swap_if_little_endian keyword to SOCKET  W. Landsman August 2002
     Less restrictive search on Content-Type   W. Landsman   April 2003
     Modified to work with FIRST image server-  A. Barth, Nov 2006
     Better recovery from errors  W. Landsman  April 2007
     Add support for POST access               J.D. Smith    June 2007
     Recognize "fits" image type used by SKYVIEW   W. Landsman  June 2007
     Upgraded, partially, to HTTP 1.1				M. Perrin, July 2007
       The HTTP 1.1 support is presently INCOMPLETE: virtual servers are
       supported, but chunked transfer encoding is not yet supported, so
       technically this is not fully HTTP 1.1 compliant.
     Added http10 keyword  W. Landsman   August 2007
     Assume since V5.6, sockets always available  W. Landsman Nov 2007
     Fix problem when using proxy server   W. Landsman July 2008
     Fix problem with /SILENT keyword  W. Landsman  Jan 2009
     Added check for missing Mime TYPE in CLASSANDTYPE, Zarro, December 2011
     Timeout applies to connecting as well as reading, default is now 15
               seconds  W Landsman January 2012

(See $IDLUTILS_DIR/goddard/pro/sockets/webget.pro)

WFPC2_METRIC

 NAME:
   WFPC2_METRIC
 PURPOSE:
   Compute the distortion in a WFPC2 image and optionally return coordinates
 EPLANATION:
   Uses the distortion solution of Anderson & King (2003, PASP, 115, 113)
   Pixel 424, 424 on each chip remains fixed, and other pixel positions are
   mapped to remove nonlinearities.   If /GLOBAL is set, then all chips are
   put on the same reference frame where pixel 424, 424 in the WF3 chip 
   remains fixed. 
 CALLING SEQUENCE:
      WFPC2_METRIC, xin, yin, xout, yout, [ChipNum, HEADER=, /GLOBAL
                                           YEAR =, FILTER=
                            or
      WFPC2_METRIC, xin, yin, a, d, HEADER=, /RAdec, /GLOBAL ]
 INPUTS:
     XIN, YIN - X,Y positions (0-799) on a WFPC2 chip in 
               IDL convention (first pixel is 0,0), scalar or vectors
 OUTPUTS:
     XOUT, YOUT - X,Y positions in the undistorted frame, same number of 
                  elements as XIN, YIN
                          or if /RADEC is set
     AA, DD  - Right ascension and declination (in degrees) corresponding 
               to the input coordinates after distortion correction.
 OPTIONAL INPUT:
     ChipNum - Integer  1, 2, 3, or 4  specifying the WFPC2 chip number
             1-PC, 2-WF2, 3-WF3, 4-WF4.   If not supplied, then WFPC2_METRIC
             will try to read the value from the DETECTOR in the FITS header.
 OPTIONAL INPUTS:
     /GLOBAL - If set, then positions are returned in a master reference 
              frame with pixel 424,424 of WF3 remaining fixed.   Thus, 
              information  concerning the  interchip separation and 
              orientation (with a weak dependence on time and filter) is 
              incorporated. 
     Header - FITS header with astrometry for a particular chip.
             If both /RADec and /Global are set, then the header must be
             from the WF3 chip. 
     /RADec - If set, then astrometry information in the FITS header (which
             must be supplied as a keyword) is used to convert the output
             to Right Ascension and declination (both in degrees).
     FILTER - Filter name needed if /GLOBAL is set, must be either 'F300W'
             'F336W', 'F439W', 'F555W' or 'F814W'; otherwise the plate scale
             for F555W is assumed.   WFPC2_METRIC will try to read this 
             value from the FITS header if not supplied as a keyword.
     YEAR -  Observation year including fraction (e.g. 1998.56) needed if
             /GLOBAL is set.  WFPC2_METRIC will try to read this value from 
             the FITS header if not supplied as a keyword.  The time 
             correction is currently applied through the year 2002; later 
             dates will use the year 2002 correction.              
 EXAMPLES:
     (1) Find the undistorted X,Y coordinates of position 682.3,234.2 on chip 1 
         (the PC chip).
          IDL> WFPC2_METRIC, 682.3, 234.2, xout, yout, 1 
             ==> xout = 681.13   yout = 235.05

     (2) Determine the RA and Dec of position 682.3, 234.2 on chip 1 on the 
         WFPC2 image U2Z30201T
         IDL> WFPC2_READ, 'u2z30201t.c0h', im,h   ;Get header for chip 1
         IDL> WFPC2_METRIC, 682.3, 234.2, aa, dd, header= h,/RADec
         IDL> print, adstring(aa,dd,2)
         05 20 53.572  -69 35 18.17

         Note that a chip number did not need to be specified since its value
         is in the FITS header

     (3) As above, but now compute coordinates in the global frame, needed
         for example, to compute the distance between stars on two different
         chips. 

        First get headers for chips 1 and 3
        IDL> WFPC2_READ, 'u2z30201t.c0h', im1,h1, im3,h3,num=[1,3]   
        IDL> WFPC2_METRIC, 682.3, 234.2, aa, dd, 1, header=h3,/RADec,/GLOBAL
        IDL> print, adstring(aa,dd,2)
         05 20 53.513  -69 35 17.98

        Note that with /GLOBAL set, that the header must be for WF3, even
        though coordinates are being computed for chip 1.   Also note that
        the time and filter will be read from the FITS header.   Finally,
        note that the coordinates given in examples (2) and (3) differ
        slightly, because the chip separations incorporated in the FITS 
        headers differ slightly from those in the Anderson & King solution.   
 PROCEDURES USED:
     LINTERP, SXPAR(), XYAD, YMD2DN()
 REVISION HISTORY:
     Written     W. Landsman         March 2003

(See $IDLUTILS_DIR/goddard/pro/astrom/wfpc2_metric.pro)

WFPC2_READ

 NAME:
    WFPC2_READ

 PURPOSE:
   Read WFPC2 images in either FITS or STSDAS format into IDL variables.

 EXPLANATION:
   This a versatile procedure for reading Wide Field Planetary Camera 2 
   (WFPC2) images.   One can read either multi-extension FITS or  STSDAS or
   STSDAS converted to FITS format, and specific 
   chip or chips.    One can also read all four chips into a "batwing" mosaic--
   so-called because the PC chip (chip 1) has a plate scale of 0.045", while
   the other three WF chips have a plate scale of 0.1"
 
 CALLING SEQUENCE:
    WFPC2_READ,filename,chip1,hdr1,chip2,hdr2,chip3,hdr3,chip4,hdr4
                   or
    WFPC2_READ,filename,chip,hdr, NUM_CHIP = [1,2,3,4], [/TRIM, PATH = ]
                   or
    WFPC2_READ,filename,image,hdr,/BATWING

 INPUTS:
    filename - Name of FITS or STSDAS file with a stack of images from
            the four WF/PC-2 chips, followed by a FITS ASCII
            table with header parameters for each chip.    If the file
            name extension ends in 'h' then it is assumed to be an
            STSDAS file.   If no extension is supplied, and the file is
            is not found, then WFPC2_READ first tries appending a '.fits'
            extension, and then tries appending a '.c0h' extension.  

            The file may als be gzip compressed (with a .gz extension) 
 INPUT KEYWORD PARAMETERS:
    NUM_CHIP - Integer scalar or vector, subset of 1, 2, 3, 4, specifying 
               particular chip numbers to read.    Outputs will be in same 
               order as specification of subset.   (See Example 2.)
    /TRIM   - If set, trim off areas with no image and re-orient so that
              all  the chips have a common orientation suitable for insertion 
               into "bat-wing" mosaic (no image distortion removal, however).
    PATH   -   scalar string specifying a !PATH-like list of directories
               in which to search for the file.   Default is to look only
               in the current directory.
    /BATWING -  Return a 1600 x 1600 array containing all four chips in a
               "bat wing" mosaic formation.     This image is mainly for 
               display  purposes, since the PC chip is compressed to match the plate 
               scale of the WF chips.    In addition, a small astrometry error
               is introduced since chips do not have the same rotation, nor    
               are they aligned at the integer pixel level.
 OUTPUTS:
    chipN    - 800 X 800 image from chip N.   If /TRIM is set then the output
               size is somewhat smaller (e.g. 756 x 757)
    headerN  - Individual FITS header for chip N with correct astrometry.

 PROCEDURES USED:
     For FITS I/O: FITS_CLOSE, FITS_OPEN, FITS_READ
     For STSDAS I/O: EXTGRP, FTGET(), SXOPEN, SXREAD()
     Other procedures:  CHECK_FITS, FDECOMP, FIND_WITH_DEF(), FREBIN, HEXTRACT, 
           HROTATE, SXADDHIST, SXADDPAR, SXPAR()
 EXAMPLE: 
    (1) Read all four chips of the FITS file u2ou0201t_c0f.fits
 
    IDL> wfpc2_read,'u2ou0201t_c0f',c1,h1,c2,h2,c3,h3,c4,h4

     (2) Note that supplying the .fits extension is optional.   Now read only
     chips 1 (the PC chip) and 3.   Trim off portions of the arrays where
     there is no image.   

    IDL> wfpc2_read,'u2ou0201t_c0f',c1,h1,c3,h3,num=[1,3],/trim

      (3) Note that with the /TRIM option the output chip sizes are no longer
          800 x 800 but odd sizes such as 770 by 753.    Now read all 4 chips
          into a 1600 x 1600 "batwing" mosaic

    IDL> wfpc2_read,'u2ou0201t_c0f',im,h,/batwing

 MODIFICATION HISTORY:
     Written by W. Landsman, Raytheon STX, for IDL V5.0     June 1998
     Based on code by Robert Hill, Raytheon STX
     Better astrometry of PC image in "batwing" configuration, W. Landsman
                August 1999
     Use vector call to SXADDHIST  W. Landsman   March 2003
     Don't use EXECUTE() for V6.1 or later W. Landsman Dec 2006
     Assume since V6.1  W. Landsman  June 2009
     Ability to read multi-extension format FITS  W. Landsman May 2010
     Correct header in MEF form when only reading PC chip.  W.L. July 2010

(See $IDLUTILS_DIR/goddard/pro/disk_io/wfpc2_read.pro)

WHERENAN()

 NAME:
      WHERENAN()
 PURPOSE:
      Find the indices of all big-endian NaN values in an array.  OBSOLETE
 EXPLANATION: 
      Find the positions of all values within an array that correspond to the
      big-endian NaN (not-a-number) special values.    

      THIS PROCEDURE ONLY IDENTIFIES BIG_ENDIAN NaN VALUES.  DO NOT USE IT 
      TO IDENTIFY NaN VALUES IN GENERAL.   Instead, to identify NaN values on 
      the host machine use the FINITE() function 

      IDL>     result = where( finite(array,/NAN) )
       
      The main purpose of this routine is to catch  NaN special values 
      written in big_endian format (e.g. FITS data) on a little endian 
      machine prior to conversion with e.g. IEEE_TO_HOST.    It was needed
      many years ago because VMS machines could not handle big-endian 
      special values, but this routine is now kept only for backwards 
      compatibility.

 CALLING SEQUENCE:
      Result = WHERENAN( ARRAY [, COUNT ] )

 INPUT PARAMETERS:
      ARRAY   = Array to test against the IEEE NaN special values.  Must be
                of either floating point, double-precision, or complex type.

 OUTPUTS:
      The result of the function is the indices of all values of ARRAY
      corresponding to the IEEE NaN specification, similar to the IDL WHERE
      function.

 OPTIONAL OUTPUT PARAMETERS:
      COUNT   = Number of values found corresponding to IEEE NaN.

 SIDE EFFECTS:
      If no NaN values are found, or if ARRAY is not of type float, double
      precision, or complex, then -1 is returned, and COUNT is set to 0.

 RESTRICTIONS:
      ARRAY must be of type float, double-precision, or complex.

 PROCEDURE:
      The bit patterns of the numbers being tested are compared against the
      IEEE NaN standard.

 MODIFICATION HISTORY:
      William Thompson, Feb. 1992.
      William Thompson, Oct. 1992, fixed bug regarding order of bytes on VAX
              machines.
      Converted to IDL V5.0   W. Landsman   September 1997

(See $IDLUTILS_DIR/goddard/pro/misc/wherenan.pro)

WHERE_TAG

 NAME:
	WHERE_TAG
 PURPOSE:
	Like WHERE but works on structure tag names
 EXPLANATION:
	Obtain subscripts of elements in structure array for which
	a particular Tag has values in a range or matching specified values.
	Like the WHERE function but for use with structures
 CATEGORY:
			Structures
 CALLING SEQUENCE:
	 w = where_tag( struct, [ Nfound,  TAG_NAME=, TAG_NUMBER = , RANGE =, 
				VALUES =, RANGE =, ISELECT =, /NOPRINT ]

 INPUTS:
	Struct = structure array to search.

 INPUT KEYWORDS:
	User *must* specify (1) TAG_NAME or TAG_NUMBER to search, and (2)
		the VALUES or RANGE to search on

	TAG_NAME = Scalar string specifying Tag Name
	TAG_NUMBER = otherwise give the Tag Number,
	RANGE = [min,max] range to search for in Struct,
	VALUES = one or array of numbers to match for in Struct,
	ISELECT= specifies indices to select only part of structure array,
		(use it to recycle subscripts from previous searches).
	/NOPRINT = suppress informational messages about nothing found.

 OUTPUTS:
	Nfound = # of occurences found.

 RESULT:
	Function returns subscripts (indices) to desired elements.

 EXAMPLES:
	Suppose STR is a structure with tags CAT_NO:indgen(10), and 
		NAME:strarr(10).   Find the indices where STR.CAT_NO is
		between 3 and 5.

	IDL> print, WHERE_TAG( str, TAG_NAME = 'CAT_NO', VALUE = [3,4,5] )  ;or
	IDL> print, WHERE_TAG( str, TAG_NUM = 0, RANGE = [3,5]) 

 PROCEDURE:
	Get tag number and apply the WHERE function appropriately.

 MODIFICATION HISTORY:
	written 1990 Frank Varosi STX @ NASA/GSFC
	Stop printing "Tag <xxx> not found" with /NOPRINT, CD Pike 8-Jun-93
       Use STRJOIN for display  W.L. July 2009

(See $IDLUTILS_DIR/goddard/pro/structure/where_tag.pro)

WINDOWAVAILABLE

 NAME:
       WindowAvailable

 PURPOSE:

       This function returns a 1 if the specified window index number is
       currently open or available. It returns a 0 if the window is currently
       closed or unavailable.

 AUTHOR:

       FANNING SOFTWARE CONSULTING
       David Fanning, Ph.D.
       1645 Sheely Drive
       Fort Collins, CO 80526 USA
       Phone: 970-221-0438
       E-mail: david@idlcoyote.com
       Coyote's Guide to IDL Programming: http://www.idlcoyote.com

 CATEGORY:

       Utilities

 CALLING SEQUENCE:

       available = WindowAvaiable(windowIndexNumber)

 INPUTS:

       windowIndexNumber:   The window index number of the window you wish to
                            know is available or not.

 KEYWORDS:

       None.

 NOTES:

       The window vector obtained from the DEVICE command is not always the same length. It
       is normally (on my machine) 65 elements long, but can be much longer if you have lots
       of IDL windows open (by calling PickColorName, for example). But if no windows with 
       index numbers greater than 65 are open, IDL shinks the larger vector to the smaller one
       as part of its housekeeping operations, which means it happens on their timetable, not yours.
       This can result in the user having "stale" index numbers greater than 65, but no larger vector
       to check them against. I have modified the code to return a 0 in this case, assuming that
       whatever window your index number points to is long gone. I have not experience any ill effects
       by doing this, but I STRONGLY advice you to ALWAYS know what window you are drawing into
       when you issue a graphics command.

 MODIFICATION HISTORY:

       Written by David W. Fanning, June 2005.
       Modified to return 0 if the window index number is larger than the number of elements
             in the WINDOW_STATE array. 25 June 2008. DWF.

(See $IDLUTILS_DIR/goddard/pro/coyote/windowavailable.pro)

WRITEFITS

 NAME:
       WRITEFITS
 PURPOSE:
       Write IDL array and header variables to a disk FITS file.    

 EXPLANATION:
       A minimal FITS header is created if not supplied.
       WRITEFITS works for all types of FITS files except random groups

 CALLING SEQUENCE:
       WRITEFITS, filename, data [, header, /APPEND, /COMPRESS, /CHECKSUM] 

 INPUTS:
       FILENAME = String containing the name of the file to be written.

       DATA = Image array to be written to FITS file.    If DATA is 
              undefined or a scalar, then only the FITS header (which
              must have NAXIS = 0) will be written to disk

 OPTIONAL INPUT:
       HEADER = String array containing the header for the FITS file.
                If variable HEADER is not given, the program will generate
                a minimal FITS header.
       HEAP -   A byte array giving the heap area following, e.g. a variable
                length binary table

 OPTIONAL INPUT KEYWORD:
       /APPEND - If this keyword is set then the supplied header and data
                array are assumed to be an extension and are appended onto
                the end of an existing FITS file.    If the file does not 
                exist, then WRITEFITS will create one with a minimal primary
                header (and /EXTEND keyword) and then append the supplied
                extension header and array.     Note that the primary
                header in an existing file must already have an EXTEND
                keyword to indicate the presence of an FITS extension.
       /COMPRESS - If this keyword is set, then the FITS file is written as
                a gzip compressed file.   An extension '.gz' is appended to
                to the file name if it does not already exist.   The /COMPRESS
                option is incompatible with the /APPEND option.
      /Checksum - If set, then the CHECKSUM keywords to monitor data integrity
                 will be included in the FITS header.    For more info, see
                  http://heasarc.gsfc.nasa.gov/docs/heasarc/fits/checksum.html
                 By default, checksum keywords will updated if they are already
                 in the FITS header.
       NaNvalue - Value in the data array which represents missing pixels.
		 This keyword is only used when missing pixels are not
		 represented by NaN values in the input array.
 OUTPUTS:
       None

 RESTRICTIONS:
       (1) It recommended that BSCALE and BZERO not be used (or set equal
           to 1. and 0) except with integer data
       (2) WRITEFITS will remove any group parameters from the FITS header
       (3) As of Feb 2008, WRITEFITS no longer requires the primary header of a
           FITS file with extension contain the EXTEND keyword, consistent with 
           the draft revised FITS standard.    A warning is still given.
           http://fits.gsfc.nasa.gov/fits_draft.html

 EXAMPLE:
       Write a randomn 50 x 50 array as a FITS file creating a minimal header.

       IDL> im = randomn(seed, 50, 50)        ;Create array
       IDL> writefits, 'test', im             ;Write to a FITS file "test"

 PROCEDURES USED:
       CHECK_FITS, FITS_ADD_CHECKSUM, MKHDR, MRD_HREAD, SXDELPAR, SXADDPAR, 
       SXPAR()

 MODIFICATION HISTORY:
       WRITTEN, Jim Wofford, January, 29 1989
       Added call to IS_IEEE_BIG()  W. Landsman  Apr 96
       Make sure SIMPLE is written in first line of header  W. Landsman Jun 97
       Use SYSTIME() instead of !STIME    W. Landsman  July 97
       Create a default image extension header if needed W. Landsman June 98
       Write unsigned data types W. Landsman       December 1999
       Update for IDL V5.3, add /COMPRESS keyword W. Landsman  February 2000
       Correct BZERO value for unsigned data  W. Landsman   July 2000
       Eliminate duplication of input array if possible W. Landsman April 2001
       Use FILE_SEARCH for V5.5 or later     W. Landsman    April 2002
       Create the file if not already present and /APPEND is set
                                             W. Landsman    September 2002
       Proper call to MRD_HREAD if /APPEND is set  W. Landsman December 2002 
       Added /CHECKSUM keyword              W. Landsman     December 2002
	Restored NANvalue keyword, William Thompson,	     October 2003
       Write BZERO in beginning of header for unsigned integers WL April 2004
       Added ability to write heap array       WL             October 2004
       Correct checksum if writing heap array   WL           November 2004
       Assume since V5.5, no VMS support, use file_search() WL   September 2006
       Set nbytes variable to LONG64 for very large files WL  May 2007
       Update CHECKSUM keywords if already present  WL   Oct 2007
       EXTEND keyword no longer required in FITS files with extensions WL Feb 2008
       Bug fix when filename ends with '.gz' and COMPRESS is used,
            the output file must be compressed          S. Koposov June 2008 
      Use V6.0 notation  WL  Feb 2011

(See $IDLUTILS_DIR/goddard/pro/fits/writefits.pro)

XDISPSTR

  NAME:      
     XDISPSTR

  PURPOSE:   
     Display a string array in a text widget with a simple search capability.

 EXPLANATION:
     Similar to the IDL XDISPLAYFILE procedure but includes a search capbility.
 CALLING SEQUENCE:    
                 
     xdispstr, array, [/BLOCK, WIDTH= , HEIGHT=, TITLE=, GROUP_LEADER=, FONT=
                       TOP_LINE = ]

 INPUT PARAMETER:

     array  - String array (.e.g. FITS header) to be displayed

  OPTIONAL INPUT KEYWORD PARAMETERS:

    block -  Set to 1 to make widget blocking.  Default = block=0
          
    width, height  - Scalars giving number of characters per line, number
                           of lines.  Default = 80x24

    title  - Scalar Title for outermost base widget.

    group_leader  -    Group leader for top level base.

    top_line - first line in the string array to display (default is 0)

    font  -     Display font for text.

  MODIFICATION HISTORY:
     Written by R. S. Hill, RITSS, 17 Nov 2000
     Use cumulative keyword to TOTAL   W. Landsman   May 2006

(See $IDLUTILS_DIR/goddard/pro/misc/xdispstr.pro)

XMEDSKY

 NAME:
       XMEDSKY

 PURPOSE:
       Subtract sky from an image as a 1-D function of X
 EXPLANATION:
       This procedure is designed to remove the sky from slitless spectra.
       The sky is assumed to vary with wavelength (along a row) but not with
       position (along a column).    The sky is computed as the 
       column-by-column median of pixels within 3 sigma of the image global 
       median.   This procedure is called by the cosmic ray rejection routine
       CR_REJECT

 CALLING SEQUENCE:
       XMEDSKY, Image, Bkg, [ CLIP=[x0, x1, y0, y1], NSIG= ]

 INPUTS:
       Image:  Input image for which sky vector is to be computed.
       
 INPUT KEYWORD PARAMETERS:
       CLIP:   [x0, x1, y0, y1]: region of image to be used for all
               statistical computations.    Default is to use the entire
               image.   For STIS 1024 x 512 slitless spectra, the suggested
               value is CLIP = [32,1023,12,499]
       NSIG:   Positive scalar giving the number of sigma a pixel must be above
               the global median to be reject.   Default is 3 sigma.
 OUTPUT PARAMETER:
       Bkg:    Vector of sky values.
;
 MODIFICATION HISTORY:
       Written by:     R. S. Hill, Hughes STX, 20 Oct. 1997
       Converted to V5.0, use STDDEV()   W. Landsman   June 1998
       Check for valid WHERE, added NSIG keyword  W. Landsman   December 2000 
       Assume since V5.1 so always use STDDEV  W. Landsman Feb 2004 
       Assume since V5.6 use DIMEN keyword to MEDIAN W. Landsman Jan 2008

(See $IDLUTILS_DIR/goddard/pro/image/xmedsky.pro)

XY2AD

 NAME:
     XY2AD

 PURPOSE:
     Compute R.A. and Dec from X and Y and a FITS astrometry structure
 EXPLANATION:
     The astrometry structure must first be extracted by EXTAST from a FITS
     header.   The offset from the reference pixel is computed and the CD 
     matrix is applied.     If distortion is present then this is corrected.
     If a WCS projection (Calabretta & Greisen 2002, A&A, 395, 1077) is 
     present, then the procedure WCSXY2SPH is used to compute astronomical
     coordinates.    Angles are returned in  degrees.
   
     XY2AD is meant to be used internal to other procedures.  
     For interactive purposes use XYAD.

 CALLING SEQUENCE:
     XY2AD, x, y, astr, a, d   

 INPUTS:
     X     - row position in pixels, scalar or vector
     Y     - column position in pixels, scalar or vector
           X and Y should be in the standard IDL convention (first pixel is
           0), and not the FITS convention (first pixel is 1). 
     ASTR - astrometry structure, output from EXTAST procedure containing:
        .CD   -  2 x 2 array containing the astrometry parameters CD1_1 CD1_2
               in DEGREES/PIXEL                                   CD2_1 CD2_2
        .CDELT - 2 element vector giving physical increment at reference pixel
        .CRPIX - 2 element vector giving X and Y coordinates of reference pixel
               (def = NAXIS/2)
        .CRVAL - 2 element vector giving R.A. and DEC of reference pixel 
               in DEGREES
        .CTYPE - 2 element vector giving projection types 
        .LONGPOLE - scalar longitude of north pole
        .LATPOLE - scalar giving native latitude of the celestial pole
        .PV2 - Vector of projection parameter associated with latitude axis
             PV2 will have up to 21 elements for the ZPN projection, up to 3
             for the SIN projection and no more than 2 for any other
             projection
        .DISTORT - Optional substructure specifying distortion parameters
                  

 OUTPUT:
     A - R.A. in DEGREES, same number of elements as X and Y
     D - Dec. in DEGREES, same number of elements as X and Y

 RESTRICTIONS:
       Note that all angles are in degrees, including CD and CRVAL
       Also note that the CRPIX keyword assumes an FORTRAN type
       array beginning at (1,1), while X and Y give the IDL position
       beginning at (0,0).   No parameter checking is performed.

 NOTES:
      AD2XY tests for presence of WCS coordinates by the presence of a dash 
      in the 5th character position in the value of CTYPE (e.g 'DEC--SIN').       
 PROCEDURES USED:
       TAG_EXIST(), WCSXY2SPH
 REVISION HISTORY:
       Written by R. Cornett, SASC Tech., 4/7/86
       Converted to IDL by B. Boothman, SASC Tech., 4/21/86
       Perform CD  multiplication in degrees  W. Landsman   Dec 1994
       Understand reversed X,Y (X-Dec, Y-RA) axes,   W. Landsman  October 1998
       Consistent conversion between CROTA and CD matrix W. Landsman Oct. 2000
       No special case for tangent projection W. Landsman June 2003
       Work for non-WCS coordinate transformations W. Landsman Oct 2004
       Use CRVAL reference point for non-WCS transformation  W.L. March 2007
       Use post V6.0 notation   W.L. July 2009

(See $IDLUTILS_DIR/goddard/pro/astrom/xy2ad.pro)

XYAD

 NAME:
       XYAD
 PURPOSE:
       Use a FITS header to convert pixel (X,Y) to world coordinates
 EXPLANATION: 
       Use astrometry in a FITS image header to compute world
       coordinates in decimal degrees from X and Y.    

       If spherical coordinates (Calabretta & Greisen 2002, A&A, 395, 1077) are 
       not present, then XYAD will still perform the transformation specified
       by the CD, CRVAL, and CRPIX keywords.
 CALLING SEQUENCE:
       XYAD, HDR               ;Prompt for X and Y positions
       XYAD, HDR, X, Y, A, D, [ /PRINT, /Galactic, /Celestial, /Ecliptic, 
                                ALT =, PRECISION=]
 INPUTS:
       HDR - FITS Image header containing astrometry info

 OPTIONAL INPUTS:
       X     - row position in pixels, scalar or vector
       Y     - column position in pixels, scalar or vector

       X and Y should be in IDL convention, (first pixel is (0,0) where
       the integral value corresponds to the center of the pixel.)

 OPTIONAL OUTPUT:
       A - Output longitude in decimal DEGREES (for spherical coordinates), 
               same number of elements as X and Y.    For celestial 
               coordinates, this is the Right ascension.
       D - Output latitude in decimal DEGREES.   For celestial coordinates,
               this is the declination.
 OPTIONAL KEYWORD INPUT:
       ALT -  single character 'A' through 'Z' or ' ' specifying an alternate 
             astrometry system present in the FITS header.    The default is
             to use the primary astrometry or ALT = ' '.   If /ALT is set, 
             then this is equivalent to ALT = 'A'.   See Section 3.3 of 
             Greisen & Calabretta (2002, A&A, 395, 1061) for information about
             alternate astrometry keywords.
       PRECISION - Integer scalar (0-4) specifying the number of digits 
             displayed after the decimal of declination.   The RA is
             automatically one digit more.   See ADSTRING() for more info.
             Default value is 1, and the keyword is ignored if results are not 
             displayed at the terminal 
       /PRINT - If this keyword is set and non-zero, then results are displayed
               at the terminal.in both decimal and sexigesimal notation.

       The default for XYAD is to return the coordinate system present in
       in the FITS header.    However, the following mutually exclusive 
       keywords can be used to convert to a particular coordinate system:

       /CELESTIAL - Output is Right Ascension and declination
       /ECLIPTIC - Output is Ecliptic longitude and latitude
       /GALACTIC - Output is Galactic longitude and latitude
    
 OPERATIONAL NOTES:
       If less than 5 parameters are supplied, or if the /PRINT keyword is
       set, then the computed astronomical coordinates are displayed at the 
       terminal.

       If this procedure is to be used repeatedly with the same header,
       then it would be faster to use XY2AD.

 EXAMPLE:
       A FITS header, hdr, contains astrometric information in celestial
       coordinates.   Find the RA and Dec corresponding to position X=23.3
        Y = 100.2 on an image
        IDL> xyad, hdr, 23.3, 100.2      ;Displays results at the terminal
       To display the results in Galactic coordinates
        IDL> xyad, hdr, 23.3, 100.2, /GALACTIC

 PROCEDURES CALLED
       ADSTRING(), EULER, EXTAST, GSSSXYAD, REPCHR(),  XY2AD

 REVISION HISTORY:
       W. Landsman                 STX          Jan, 1988
       Use astrometry structure  W. Landsman    Jan, 1994
       Recognize GSSS header  W. Landsman       June, 1994
       Changed ADSTRING output format   W. Landsman    September 1995
       Converted to IDL V5.0   W. Landsman   September 1997
       Use vector call to ADSTRING() W. Landsman February 2000
       Added ALT input keyword  W. Landsman June 2003
       Add precision keyword  W. Landsman February 2004
       Fix display if 'RA','DEC' reversed in CTYPE  W. Landsman Feb. 2004
       Handle display of NaN values W. Landsman May 2004
       Work for non-spherical coordinate transformations W. Landsman Oct 2004
       Fix output display units if ALT keyword used W. Landsman March 2005
       More informative error message if no astrometry present W.L Nov 2007
       Fix display when no equinox in header W.L. Dec 2007
       Fix header display for noncelestial coords W.L. Jan 2008

(See $IDLUTILS_DIR/goddard/pro/astrom/xyad.pro)

XYXY

 NAME:
	XYXY
 PURPOSE:
	To use a pair of headers to convert X/Y positions from one frame
	to another.
 CALLING SEQUENCE:
	XYXY, hdra, hdrb, xa, ya, [ xb, yb ]
 INPUTS:
	hdra - The header containing the plate solution describing the
	       frame of reference being converted FROM.
	hdra - The header containing the plate solution describing the
	       frame of reference being converted TO.
	xa   - A scalar or vector containing the x coordinate(s) to convert.
	ya   - A scalar or vector containing the y coordinate(s) to convert.
	       Must have the same number of elements as 'xa'.
 OUTPUTS:
	xb   - The converted x coordinate(s).  If this parameter is not
	       specified, it is returned through 'xa'.
	yb   - The converted y coordinate(s).  If this parameter is not
	       specified, it is returned through 'ya'.
 PROCEDURE:
	The procedures 'xyad' and 'adxy' are used to perform the 
       conversion.     The equinoxes of each header are checked with
       "get_equinox" to make sure that they are identical, and "precess"
       is used if they are not.   HEULER used if the headers have a different
       coordinate system (e.g. Celestial, Galactic, Ecliptic)

       Note that all X,Y coordinates are in the IDL convention (starting with
       0,0) and not the FITS convention (first pixel is 1,1)
 PROCEDURES USED:
	GET_EQUINOX(), EXTAST, XYAD, ADXY, PRECESS, HEULER
 MODIFICATION HISTORY:
	Written by Michael R. Greason, Hughes-STX, 13 April 1992.
	Updated to use ASTROMETRY structures.  J.D.Offenberg, HSTX, Jan 1993
	Converted to IDL V5.0   W. Landsman   September 1997
       Check coordinate system   J. Ballet/ W. Landsman  April 2004

(See $IDLUTILS_DIR/goddard/pro/astrom/xyxy.pro)

XYZ

 NAME:
       XYZ
 PURPOSE:
       Calculate geocentric X,Y, and Z  and velocity coordinates of the Sun
 EXPLANATION:
       Calculates geocentric X,Y, and Z vectors and velocity coordinates 
       (dx, dy and dz) of the Sun.   (The positive X axis is directed towards 
       the equinox, the y-axis, towards the point on the equator at right 
       ascension 6h, and the z axis toward the north pole of the equator).
       Typical position accuracy is <1e-4 AU (15000 km).

 CALLING SEQUENCE:
       XYZ, date, x, y, z, [ xvel, yvel, zvel, EQUINOX = ]

 INPUT:
       date: reduced julian date (=JD - 2400000), scalar or vector

 OUTPUT:
       x,y,z: scalars or vectors giving heliocentric rectangular coordinates
                 (in A.U) for each date supplied.    Note that sqrt(x^2 + y^2
                 + z^2) gives the Earth-Sun distance for the given date.
       xvel, yvel, zvel: velocity vectors corresponding to X, Y and Z.

 OPTIONAL KEYWORD INPUT:
       EQUINOX: equinox of output. Default is 1950.

 EXAMPLE:
       What were the rectangular coordinates and velocities of the Sun on 
       Jan 22, 1999 0h UT (= JD 2451200.5) in J2000 coords? NOTE:
       Astronomical Almanac (AA) is in TDT, so add 64 seconds to 
       UT to convert.

       IDL> xyz,51200.5+64.d/86400.d,x,y,z,xv,yv,zv,equinox = 2000

       Compare to Astronomical Almanac (1999 page C20)
                   X  (AU)        Y  (AU)     Z (AU)
       XYZ:      0.51456871   -0.76963263  -0.33376880
       AA:       0.51453130   -0.7697110   -0.3337152
       abs(err): 0.00003739    0.00007839   0.00005360
       abs(err)
           (km):   5609          11759         8040 

       NOTE: Velocities in AA are for Earth/Moon barycenter
             (a very minor offset) see AA 1999 page E3
                  X VEL (AU/DAY) YVEL (AU/DAY)   Z VEL (AU/DAY)
       XYZ:      -0.014947268   -0.0083148382    -0.0036068577
       AA:       -0.01494574    -0.00831185      -0.00360365
       abs(err):  0.000001583    0.0000029886     0.0000032077
       abs(err)
        (km/sec): 0.00265        0.00519          0.00557

 PROCEDURE CALLS:
       PRECESS_XYZ
 REVISION HISTORY
       Original algorithm from Almanac for Computers, Doggett et al. USNO 1978
       Adapted from the book Astronomical Photometry by A. Henden
       Written  W. Landsman   STX       June 1989
       Correct error in X coefficient   W. Landsman HSTX  January 1995
       Added velocities, more terms to positions and EQUINOX keyword,
          some minor adjustments to calculations 
          P. Plait/ACC March 24, 1999

(See $IDLUTILS_DIR/goddard/pro/astro/xyz.pro)

YDN2MD

 NAME:
       YDN2MD
 PURPOSE:
       Convert from year and day number of year to month and day of month.       
 CALLING SEQUENCE:
       YDN2MD,yr,dy,m,d
 INPUTS:
       yr = 4 digit year (like 1988), integer scalar
       dy = day number in year (like 310), integer scalar or vector

 OUTPUTS:
       m = month number (1-12, e.g. 11 = Nov)   
       d = day of month (like 5).          
       Note: On error returns m = d = -1.

 EXAMPLE:
       Find the month/day of days 155 and 255 in the year 2001

       IDL> ydn2md, 2001, [155,255], m, d
         ==> m = [6,9]   & d = [4,12]        ; = June 4 and September 12 
       
 MODIFICATION HISTORY:
       Adapted from Johns Hopkins University/Applied Physics Laboratory
       Update to use VALUE_LOCATE,   W. Landsman    January 2001

(See $IDLUTILS_DIR/goddard/pro/astro/ydn2md.pro)

YMD2DN

 NAME:
       YMD2DN
 PURPOSE:
       Convert from year, month, day to day number of year.
 CATEGORY:
 CALLING SEQUENCE:
       dy = ymd2dn(yr,m,d)
 INPUTS:
       yr = year (like 1988).      scalar or vector
       m = month number (like 11 = Nov).   scalar or vector
       d = day of month (like 5).        scalar or vector
 KEYWORD PARAMETERS:
 OUTPUTS:
       dy = day number in year (like 310).  out
 COMMON BLOCKS:
 NOTES:
 MODIFICATION HISTORY:
       Written by R. Sterner, 20 June, 1985.
       Johns Hopkins University Applied Physics Laboratory.
       RES 18 Sep, 1989 --- converted to SUN
       R. Sterner, 1997 Feb 3 --- Made work for arrays.

 Copyright (C) 1985, Johns Hopkins University/Applied Physics Laboratory
 This software may be used, copied, or redistributed as long as it is not
 sold and this copyright notice is reproduced on each copy made.  This
 routine is provided as is without any express or implied warranties
 whatsoever.  Other limitations apply as described in the file disclaimer.txt.
	Converted to IDL V5.0   W. Landsman  2-Jan-1998

(See $IDLUTILS_DIR/goddard/pro/jhuapl/ymd2dn.pro)

ZANG

 NAME:
       ZANG
 PURPOSE:
       Determine the angular size of an object as a function of redshift
 EXPLANATION:
       Requires an input size in kpc and returns an angular size in arc seconds
       Default cosmology has a Hubble constant of 70 km/s/Mpc, Omega (matter)
       =0.3 and a normalized cosmological constant Lambda = 0.7; however these
       values can be changed with appropriate keywords.

 CALLING SEQUENCE:
       angsiz = zang( dl, [ z, H0 =, Omega_m =, Lambda0 = , q0 = , k =, 
                               /SILENT] )

 INPUTS:
       dl - linear size of the object *in kpc*, non-negative scalar or vector
       z - redshift of object, postive  scalar or vector
           Either dl and z must have the same number of elements, or at least
           one of them must be a vector.
 OPTIONAL INPUT KEYWORDS
    H0 -  Hubble constant in km/s/Mpc, default is 70

        No more than two of the following four parameters should be
        specified.    None of them need be specified, default values are given
    k - curvature constant, normalized to the closure density.   Default is
        0, indicating a flat universe
    Omega_m -  Matter density, normalized to the closure density, default
        is 0.3.   Must be non-negative
    Lambda0 - Cosmological constant, normalized to the closure density,
        default is 0.7
    q0 - Deceleration parameter, numeric scalar = -R*(R'')/(R')^2, default
        is -0.55

    Note that Omega_m + lambda0 + k = 1 and q0 = 0.5*omega_m - lambda0
 OUTPUT:
       angsiz - Angular size of the object at the given redshift in 
               arc seconds 
 EXAMPLE:
  (1) What would be the angular size of galaxy of diameter 50 kpc at a redshift
      of 1.5 in an open universe with Lambda = 0 and Omega (matter) = 0.3.
      Assume the default Hubble constant value of 70 km/s/Mpc.
      
      IDL> print,zang(50,1.5, Lambda = 0,omega_m = 0.3)
             ====> 6.58 arc seconds

  (2) Now plot the angular size of a 50 kpc diameter galaxy as a function of 
      redshift for the default cosmology (Lambda = 0.7, Omega_m=0.3) up to 
      z = 0.5
      IDL> z = findgen(50)/10. + 0.1    ;Angular size undefined at z = 0
      IDL> plot,z,zang(50,z),xtit='z',ytit='Angular Size (")'
 NOTES:
      This procedure underwent a major revision in April 2000 to allow for a 
      cosmological constant, ***including a change of the calling sequence***

      Be sure to supply the input linear size dl in units of kpc.
 PROCEDURES CALLED:
      LUMDIST() -- Calculates the luminosity distance
 REVISION HISTORY:
      Written    J. Hill   STX           July, 1988
      Converted to IDL V5.0   W. Landsman   September 1997
      Major rewrite to call LUMDIST function  W. Landsman   April 2000

(See $IDLUTILS_DIR/goddard/pro/astro/zang.pro)

ZBRENT

 NAME:
     ZBRENT
 PURPOSE:
     Find the zero of a 1-D function up to specified tolerance.
 EXPLANTION:
     This routine assumes that the function is known to have a zero.
     Adapted from procedure of the same name in "Numerical Recipes" by
     Press et al. (1992), Section 9.3

 CALLING:
       x_zero = ZBRENT( x1, x2, FUNC_NAME="name", MaX_Iter=, Tolerance=, 
                                 _EXTRA =  )

 INPUTS:
       x1, x2 = scalars, 2 points which bracket location of function zero,
                                               that is, F(x1) < 0 < F(x2).
       Note: computations are performed with
       same precision (single/double) as the inputs and user supplied function.

 REQUIRED INPUT KEYWORD:
       FUNC_NAME = function name (string)
               Calling mechanism should be:  F = func_name( px )
               where:  px = scalar independent variable, input.
                       F = scalar value of function at px,
                           should be same precision (single/double) as input.

 OPTIONAL INPUT KEYWORDS:
       MAX_ITER = maximum allowed number iterations, default=100.
       TOLERANCE = desired accuracy of minimum location, default = 1.e-3.

       Any other keywords are passed directly to the user-supplied function
       via the _EXTRA facility.
 OUTPUTS:
       Returns the location of zero, with accuracy of specified tolerance.

 PROCEDURE:
       Brent's method to find zero of a function by using bracketing,
       bisection, and inverse quadratic interpolation,

 EXAMPLE:
       Find the root of the COSINE function between 1. and 2.  radians

        IDL> print, zbrent( 1, 2, FUNC = 'COS')

       and the result will be !PI/2 within the specified tolerance
 MODIFICATION HISTORY:
       Written, Frank Varosi NASA/GSFC 1992.
       FV.1994, mod to check for single/double prec. and set zeps accordingly.
       Use MACHAR() to define machine precision   W. Landsman September 2002
       Added _EXTRA keyword  W. Landsman  December 2011
       Need to check whether user function accepts keywords W.L. Jan 2012

(See $IDLUTILS_DIR/goddard/pro/math/zbrent.pro)

ZENPOS

 NAME:
       ZENPOS
 PURPOSE:
       Return the zenith RA and Dec in radians for a given Julian date.

 CALLING SEQUENCE:
       ZENPOS, Date, Ra, Dec

 INPUT:
       Date  The Julian date, in double precision, of the date and time
               for which the zenith position is desired, scalar or vector.

 OUTPUTS:
       Ra    The right ascension in RADIANS of the zenith.
       Dec   The declination in RADIANS of the zenith.

 PROCEDURE:
       The local sidereal time is computed; this is the RA of the zenith.
       It and the observatories latitude (corresponding to the Dec.) are
       converted to radians and returned as the zenith direction.

 PROMPTS:
       ZENPOS will prompt for the following 3 parameters if they are not
       defined in the common block SITE (see below)

       LAT,LNG - north latitude and east longitude of the desired location 
               in DEGREES
       TZONE - Time Zone (in hours) of the desired location (e.g. 4 = EDT,
               5 = EST)

 COMMON BLOCKS:
       SITE - This common block should contain the three scalars LAT, LNG
               and TZONE

 PROCEDURE CALLS:
       CT2LST - Convert to Local Mean Sidereal Time
 MODIFICATION HISTORY:
       Written by Michael R. Greason, STX, 14 October 1988.
       Converted to IDL V5.0   W. Landsman   September 1997
       Update documentation, longitude now *east* of Greenwich W.L. July 2000

(See $IDLUTILS_DIR/goddard/pro/astro/zenpos.pro)

ZOOM_XY

 NAME:
      ZOOM_XY
 PURPOSE:
       Converts X, Y position on the image array to the the X,Y position 
       in the current window.   (These  positions are identical 
       only for an unroamed, zoomed image with with pixel (0,0) of the 
       image placed at position (0,0) on the TV.)

 CALLING SEQUENCE:
      ZOOM_XY, Xim,Yim,Xtv,Ytv, [ OFFSET =, ZOOM = ]

 INPUTS:
      XIM - Scalar or vector giving X position(s) as read on the image
            display (e.g. with CURSOR,XIM,YIM,/DEVICE)
      YIM - Like XTV but giving Y position(s) as read on the image display.

      If only 2 parameters are supplied then XIM and YIM will be modfied
      on output to contain the converted coordinates.

 OPTIONAL KEYWORD INPUT:
      OFFSET - 2 element vector giving the location of the image pixel (0,0) 
               on the window display.   OFFSET can be positive (e.g if the 
               image is centered in a larger window) or negative (e.g. if the
               only the central region of an image much larger than the window
               is being displayed. 
               Default value is [0,0], or no offset.

       ZOOM - Scalar specifying the magnification of the window with respect
               to the image variable.
 OUTPUTS:
      XTV,YTV - REAL*4 X and Y coordinates of the image corresponding to the
            cursor position on the TV display.   Same number of elements as
            XIM, YIM.
 COMMON BLOCKS:
       If present, ZOOM_XY will use the TV and IMAGE common blocks which are
       defined in the MOUSSE software system (see 
        http://archive.stsci.edu/uit/analysis.html)   If the user is not using
       the MOUSSE software (which keeps track of the offset and zoom in each
       window) then the common blocks are ignored.
 NOTES:
       The integer value of a pixel is assumed to refer to the *center*
       of a pixel.
 REVISON HISTORY:
       Adapted from MOUSSE procedure of the same name W. Landsman HSTX Mar 1996
       Converted to IDL V5.0   W. Landsman   September 1997
       Properly include ZOOM keyword  W. Landsman   May 2000
       Put back common blocks for MOUSSE compatibility    September 2004

(See $IDLUTILS_DIR/goddard/pro/tv/zoom_xy.pro)

ZPARCHECK