Polynomial(l)  User Contributed Perl Documentation  Polynomial(l)



NAME
       PDL::Fit::Polynomial - routines for fitting with polynomi-
       als

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(x); y(y); [o]yfit(t); [o]coeffs(s))

       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 number 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 v5.6.1                 2001-07-14              Polynomial(l)