;+
; This procedure is used to select data for later processing. 
;
; Data can be selected based on entries in the index file, such as source
; name, polarization type, IF number, etc.  For a complete list of eligible
; parameters use the procedure listcols, or see
; <a href="../toolbox/io/line_index__define.html#_LINE_INDEX::search_index">search parameters</a>.
;
; @keyword keep {in}{optional}{type=boolean} If set, the selection comes from
; the keep file.  If not set, the selection comes from the input file.
;
; @uses <a href="../toolbox/select_data.html">select_data</a>
;
; @version $Id: select.pro,v 1.5 2005/05/27 05:16:04 jbraatz Exp $
;-
PRO select, keep=keep, _EXTRA=ex
    compile_opt idl2
    if (keyword_set(keep)) then begin
        indx = select_data(!g.lineoutio,_EXTRA=ex)
    endif else begin
        indx = !g.line ? select_data(!g.lineio, _EXTRA=ex) : select_data(!g.contio, _EXTRA=ex)
    endelse
    
    if (indx[0] lt 0) then begin
        print,'No matching indices were found'
    endif else begin
        appendstack, indx
        print, 'Indices added to stack :', n_elements(indx)
    endelse
END