1Polynomial(3)         User Contributed Perl Documentation        Polynomial(3)
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NAME

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

9       This module contains routines for doing simple polynomial fits to data
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SYNOPSIS

12           $yfit = fitpoly1d $data;
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FUNCTIONS

15       fitpoly1d
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17       Fit 1D polynomials to data using min chi^2 (least squares)
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19        Usage: ($yfit, [$coeffs]) = fitpoly1d [$xdata], $data, $order, [Options...]
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21       Signature: (x(n); y(n); [o]yfit(n); [o]coeffs(order))
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23       Uses a standard matrix inversion method to do a least squares/min chi^2
24       polynomial fit to data. Order=2 is a linear fit (two parameters).
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26       Returns the fitted data and optionally the coefficients.
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28       One can thread over extra dimensions to do multiple fits (except the
29       order can not be threaded over - i.e. it must be one fixed scalar num‐
30       ber like "4").
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32       The data is normalised internally to avoid overflows (using the mean of
33       the abs value) which are common in large polynomial series but the
34       returned fit, coeffs are in unnormalised units.
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36         $yfit = fitpoly1d $data,2; # Least-squares line fit
37         ($yfit, $coeffs) = fitpoly1d $x, $y, 4; # Fit a cubic
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39         $fitimage = fitpoly1d $image,2  # Fit a quadratic to each row of an image
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41         $myfit = fitpoly1d $line, 2, {Weights => $w}; # Weighted fit
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43         Options:
44            Weights    Weights to use in fit, e.g. 1/$sigma**2 (default=1)
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BUGS

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

50       "polyfit" in PDL::Slatec
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AUTHOR

53       This file copyright (C) 1999, Karl Glazebrook (kgb@aaoepp.aao.gov.au).
54       All rights reserved. There is no warranty. You are allowed to redis‐
55       tribute this software documentation under certain conditions. For
56       details, see the file COPYING in the PDL distribution. If this file is
57       separated from the PDL distribution, the copyright notice should be
58       included in the file.
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62perl v5.8.8                       2006-08-09                     Polynomial(3)