Polynomial(3)						User Contributed Perl Documentation					     Polynomial(3)

NAME

       PDL::Fit::Polynomial - routines for fitting with polynomials

DESCRIPTION

       This module contains routines for doing simple polynomial fits to data

SYNOPSIS

	   $yfit = fitpoly1d $data;

FUNCTIONS

       fitpoly1d

       Fit 1D polynomials to data using min chi^2 (least squares)

	Usage: ($yfit, [$coeffs]) = fitpoly1d [$xdata], $data, $order, [Options...]

       Signature: (x(n); y(n); [o]yfit(n); [o]coeffs(order))

       Uses a standard matrix inversion method to do a least squares/min chi^2 polynomial fit to data. Order=2 is a linear fit (two parameters).

       Returns the fitted data and optionally the coefficients.

       One can thread over extra dimensions to do multiple fits (except the order can not be threaded over - i.e. it must be one fixed scalar num-
       ber like "4").

       The data is normalised internally to avoid overflows (using the mean of the abs value) which are common in large polynomial series but the
       returned fit, coeffs are in unnormalised units.

	 $yfit = fitpoly1d $data,2; # Least-squares line fit
	 ($yfit, $coeffs) = fitpoly1d $x, $y, 4; # Fit a cubic

	 $fitimage = fitpoly1d $image,2  # Fit a quadratic to each row of an image

	 $myfit = fitpoly1d $line, 2, {Weights => $w}; # Weighted fit

	 Options:
	    Weights    Weights to use in fit, e.g. 1/$sigma**2 (default=1)

BUGS

       May not work too well for data with large dynamic range.

SEE ALSO

       "polyfit" in PDL::Slatec

AUTHOR

       This file copyright (C) 1999, Karl Glazebrook (kgb@aaoepp.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.

perl v5.8.0							    2001-07-13							     Polynomial(3)