NAME

PDL::Fit::Gaussian - routines for fitting gaussians

DESCRIPTION

This module contains some custom gaussian fitting routines. These were developed in collaboration with Alison Offer, they do a reasonably robust job and are quite useful.

Gaussian fitting is something I do a lot of, so I figured it was worth putting in my special code.

Note it is not clear to me that this code is fully debugged. The reason I say that is because I tried using the internal linear eqn solving C routines called elsewhere and they were giving erroneous results. So steal from this code with caution! However it does give good fits to reasonable looking gaussians and tests show correct parameters.

             KGB 29/Oct/2002

SYNOPSIS

        use PDL;
        use PDL::Fit::Gaussian;
        ($cen, $pk, $fwhm, $back, $err, $fit) = fitgauss1d($x, $data);
        ($pk, $fwhm, $back, $err, $fit) = fitgauss1dr($r, $data);

FUNCTIONS

fitgauss1d

Fit 1D Gassian to data piddle

  ($cen, $pk, $fwhm, $back, $err, $fit) = fitgauss1d($x, $data);

  ($cen, $pk, $fwhm, $back, $err, $fit) = fitgauss1d($x, $data);

  xval(n); data(n); [o]xcentre();[o]peak_ht(); [o]fwhm(); 
  [o]background();int [o]err(); [o]datafit(n); 
  [t]sig(n);  [t]xtmp(n); [t]ytmp(n); [t]yytmp(n); [t]rtmp(n);

Fits a 1D Gaussian robustly free parameters are the centre, peak height, FWHM. The background is NOT fit, because I find this is generally unreliable, rather a median is determined in the 'outer' 10% of pixels (i.e. those at the start/end of the data piddle). The initial estimate of the FWHM is the length of the piddle/3, so it might fail if the piddle is too long. (This is non-robust anyway). Most data does just fine and this is a good default gaussian fitter.

SEE ALSO: fitgauss1dr() for fitting radial gaussians

fitgauss1dr

Fit 1D Gassian to radial data piddle

  ($pk, $fwhm2, $back, $err, $fit) = fitgauss1dr($r, $data);

  ($pk, $fwhm2, $back, $err, $fit) = fitgauss1dr($r, $data);

  xval(n); data(n); [o]peak_ht(); [o]fwhm(); 
  [o]background();int [o]err(); [o]datafit(n); 
  [t]sig(n);  [t]xtmp(n); [t]ytmp(n); [t]yytmp(n); [t]rtmp(n);

Fits a 1D radial Gaussian robustly free parameters are the peak height, FWHM. Centre is assumed to be X=0 (i.e. start of piddle). The background is NOT fit, because I find this is generally unreliable, rather a median is determined in the 'outer' 10% of pixels (i.e. those at the end of the data piddle). The initial estimate of the FWHM is the length of the piddle/3, so it might fail if the piddle is too long. (This is non-robust anyway). Most data does just fine and this is a good default gaussian fitter.

SEE ALSO: fitgauss1d() to fit centre as well.

BUGS

May not converge for weird data, still pretty good!

AUTHOR

This file copyright (C) 1999, Karl Glazebrook (kgb@aaoepp.aao.gov.au), Gaussian fitting code by Alison Offer (aro@aaocbn.aao.gov.au). All rights reserved. There is no warranty. You are allowed to redistribute this software / documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribution, the copyright notice should be included in the file.