;+
; Fit a baseline to the contents of the dc argument with various options.
;
; <p> This fits a set of orthogonal polynomials with a maximum order given by 
; the nfit argument to the data values in dc.  The range of
; channels to use is given by the regions and
; nregion arguments. The parameters of the fit are
; placed in the value of the polyfit argument and the rms values of the fits are
; placed in the polyrms argument.  If there is a problem, the return
; value is 0, otherwise the return value is 1.
;
; @param dc {in}{required}{type=data container} The data container to
; use.  The values to fit come from *dc.data_ptr.
; @param nfit {in}{required}{type=integer} The order of polynomial
; to fit.
; @param regions {in}{required}{type=2D array} Array describing the
; regions to use in the fit, along with nregion.  This has the same
; properties as the !g.region field in the guide structure.
; @param nregion {in}{required}{type=integer} The number of regions in
; regions to actually use.
; @param polyfit {out}{type=double array} Parameters describing the
; polynomials.  Array with (nfit+1) elements.  See <a
; href="ortho_fit.html">ortho_fit<a> for more details.
; @param polyrms {out}{type=double array} RMS values, one for each
; polynomial (nfit+1).
;
; @returns 1 on success, 0 on failure.
;
; @examples
; <pre>
;   ok = dcbaseline(!g.s[0], 2, !g.regions, !g.nregion, polyfit, polyrms)
; </pre>
;
; @uses <a href="data_valid.html">data_valid</a>
; @uses <a href="get_chans.html">get_chans</a>
; @uses <a href="ortho_fit.html">ortho_fit</a>
;
; @version $Id: dcbaseline.pro,v 1.1 2004/12/08 03:50:36 bgarwood Exp $
;-
function dcbaseline, dc, nfit, regions, nregion, polyfit, polyrms
   compile_opt idl2

   if (data_valid(dc) lt 1) then begin
       message, 'The data container to be fit has no valid data in it.', /info
       return, 0
   endif

   if (nfit < 0) then begin
       message, 'nfit must be >= 0', /info
       return, 0
   endif

   chans = get_chans(dc, nregion, regions)
   if (chans[0] < 0) then begin
       message, 'The nregions are invalid',/info
       return, 0
   endif
   polyfit = ortho_fit(chans,(*dc.data_ptr)[chans], nfit, cfit, polyrms)
   return, 1
end