idlastro / FITS ASCII & Binary Table I/O: FTAB_EXT

[Source code]

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,..,v50, 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,...,v50 - values for the columns.   Up to 50 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.    This keyword
        works for ASCII tables and binary tables where every column has
        the same number of elements, but not for variable length 
        binary tables.
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
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
Setting ROWS = -1 should work as documented, accept up to 50
        columns  W.L.  Oct 2013