Re: ascii files from isis

    Saku> Once I have a fit that I like in Isis how do I write the model onto an
    Saku> ascii file?  E.g. in Sherpa one says 

    Saku> sherpa:  write model filename.ascii

    Saku> (I like to do all my plots in sm)


Hi Saku - 

There isn't a canned routine, but it isn't hard to define one.
Here's a snippet from an  example I wrote:


  (w_lo, w_hi) = linear_grid( 1.0, 8192*0.005 + 1.0, 8192 ); % MEG grid
  y = eval_fun( w_lo, w_hi );       % evaluate the model on the grid

  e_lo = HC / w_hi ;             % make an energy grid
  e_hi = HC / w_lo ;

  variable egrid, s;

  egrid = reverse( 0.5*(e_lo + e_hi) ) ;     % keV, ascending order,  for marx
  s = reverse (y / (e_hi-e_lo) );            % convert to phot/cm^2/s/keV

  %  print out the integrated photon flux; useful for marx flux param
  () = printf("Integrated flux = %g [phot/cm^s/s] (1-40A)\n",  sum(y) ); 

  variable i, fp=fopen( file, "w");

  () = fprintf(fp, "# APED model spectrum\n");
  () = fprintf(fp, "# Integrated flux = %g [phot/cm^s/s] (1-40A)\n",  sum(y) ); 
  () = fprintf(fp, "\n" ); 

  for (i=0; i<length(s); i++)
    ()=fprintf(fp, "%10.6f\t%S\n", egrid[i],   s[i] );

  () = fclose(fp);



-- Dave

David Huenemoerder (617-253-4283; fax: 253-8084)
MIT Center for Space Research/Chandra X-ray Center
70 Vassar St., NE80-6023,
Cambridge, MA  02139
[Admin. Asst.: Deborah Gage 617-253-0228, dgage_at_email.domain.hidden


For reference, here's the whole function:


%; Time-stamp: <2002-10-05 14:20:54 dph> 
%; Directory: ~dph/h3/CXC/Prop_Planning/
%; File: mk_marx_spectrum.sl
%; Author: D. Huenemoerder
%; Original version: 2002.10.04
%;====================================================================
% version: 1
%
% PURPOSE:
%
%    simple demonstration of how to make a model multi-temperature
%    thermal plasma spectrum with non-cosmic abundances, written to
%    and ascii table for marx input.  
%
% REQUIRES: isis version 1.0.25 or greater for the create_aped_fun function.
%           aped plasma database must be loaded.
%
% NOTE: there is no error checking done here!
%
%%%%%%%%%

define mk_marx_spectrum( file, LogT, Norm, Elem, Abund )
{

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% example usage: 
%
% isis> plasma(aped);
% isis> evalfile("mk_marx_spectrum.sl");
% isis> mk_marx_spectrum( "Mdl_1.tbl", [6.5, 6.8, 7.1], [0.001, 0.01, 0.005], [Fe,Ne], [0.1, 2.0]);

% creates model spectrum with  3 temperature components
%          at LogT= 6.5, 6.8, 7.1, 
%          in 1:10:5 relative weights emission measure
%          1/10 Cosmic Fe abundance, 2*Ne abundance.
%
% (Note: emission measure normalization are DEM * 1.e-14 / (4*PI*d^2) )
%
% input arrays can be any length.
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

  variable p, w_lo, w_hi, e_lo, e_hi, y;
  variable HC = 12.3984185734;
  
  p = default_plasma_state;   % retrieve plasma structure variable

  p.norm = Norm ;               % set appropriate fields of the structure
	                        % NO checking! inputs must be meaningful.
  p.temperature = 10.^LogT ; 
  p.elem = Elem ;
  p.elem_abund = Abund ;

  create_aped_fun("xaped", p);   %  create the function
  fit_fun("xaped(1)");           %  use the function as the spectral model.

  (w_lo, w_hi) = linear_grid( 1.0, 8192*0.005 + 1.0, 8192 ); % MEG grid

  y = eval_fun( w_lo, w_hi );       % evaluate the model on the grid

  e_lo = HC / w_hi ;             % make an energy grid
  e_hi = HC / w_lo ;

  variable egrid, s;

  egrid = reverse( 0.5*(e_lo + e_hi) ) ;     % keV, ascending order,  for marx
  s = reverse (y / (e_hi-e_lo) );            % convert to phot/cm^2/s/keV

  %  print out the integrated photon flux; useful for marx flux param
  () = printf("Integrated flux = %g [phot/cm^s/s] (1-40A)\n",  sum(y) ); 

  variable i, fp=fopen( file, "w");

  () = fprintf(fp, "# APED model spectrum\n");
  () = fprintf(fp, "# Integrated flux = %g [phot/cm^s/s] (1-40A)\n",  sum(y) ); 
  () = fprintf(fp, "\n" ); 

  for (i=0; i<length(s); i++)
    ()=fprintf(fp, "%10.6f\t%S\n", egrid[i],   s[i] );

  () = fclose(fp);
        
  return w_lo, w_hi, y;

}
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