If you can't find a module that does cross-correlation, you can always use one of the many FFT implementations - in pseudo-code:

# input arrays are @f and @g, this calculates @cc which is the cross-c
+orrelation of these.
@Ff = fft(@f);
@Fg = fft(@g);
@Fcc = complex_conjugate(@Ff) * @Fg;
@cc = inverse_fft(@Fcc);

[download]

This makes use of the fourth of the properties listed here. If your input arrays are purely real, I think it may be possible to optimise this further by performing their FFTs in a single FFT calculation, with a bit of clever maths.

I did calculation of a cross-correlation using this method some years ago, but it wasn't in Perl, unfortunately.

--

"Any sufficiently analyzed magic is indistinguishable from science" - Agatha Heterodyne

In reply to Re: Calculating cross-correlation by mykl
in thread Calculating cross-correlation by Anonymous Monk

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