# RedHat 9 (Linux i386) - man page for pdl::fit::gaussian (redhat section 3)

```Gaussian(3)						User Contributed Perl Documentation					       Gaussian(3)

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 this code is also used in the Karma package.

SYNOPSIS
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, \$fwhm2, \$back, \$err, \$fit) = fitgauss1d(\$x, \$data);

(\$cen, \$pk, \$fwhm2, \$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);

Fit's 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 esti-
mate 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.

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);

Fit's 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.