SeigePerlous has asked for the wisdom of the Perl Monks concerning the following question:

Maybe I'm just so new to Perl, or I'm not looking in the right place, but I can't find anything that states the organization of the fitted values returned from fitpoly1d in this module. I figured it was an array (vector) but pp tells me otherwise... 
pp($yFit);
yFit:
bless(do{\(my $o = 100732500)}, "PDL")
Argument "[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0..."
+ isn't numeric in multiplication (*) at Y:\GUI\..\
CommonModules/UnitConverter.pm line 185, <GEN1> line 1617.

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What exactly does fitpoly1d return and how do I simply get the fitted values? Thanks!

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Re: PDL::Fit::Polynomial return values
by zentara (Cardinal) on Oct 14, 2011 at 18:25 UTC
    Your example code dosn't show much, here is an example pulled from the PDL maillist. See also output from fitpoly1d 
    #!/usr/bin/perl
use PDL;
use PDL::MATH;
use PDL::Fit::Polynomial;

my $xdata = sequence float, 16;
my $ydata = sequence float, 16;

my $i = 0;
 while ($i < 16) {
    $xdata[$i] = $i;
    $ydata[$i] = $i * $i;
    
   print "i ", $i, " x ", $xdata[$i], " y ", $ydata[$i], "\n";
    $i++;
 }

 ($yfit, $coeffs) = fitpoly1d $xdata, $ydata, 3;

 print "Fit complete with coeffs ", $coeffs, "\n";

 print "Fitted values ", $yfit, "\n";

 $i = 0;
 while ($i < 16) {
    print "i ", $i, " yfit ", $yfit[$i], "\n";
    $i++;
 }

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