[SciPy-dev] Fixing correlate: handling api breakage ?

David Cournapeau david@ar.media.kyoto-u.ac...
Sun May 24 05:16:05 CDT 2009


Hi,

    I have taken a look at the correlate function in scipy.signal. There
are several problems with it. First, it is wrong on several accounts:
       - It assumes that the correlation of complex numbers corresponds
to complex multiplication, but this is not the definition followed by
most textbooks, at least as far as signal processing is concerned.
       - More significantly, it is wrong with respect to the ordering:
it assumes that correlate(a, b) == correlate(b, a), which is not true in
general.

It may be argued that the first problem is a matter of definition, but I
don't think the 2nd one is. I would expect some people depending on the
functionality, though. What should we do ? Adding a new function which
implements the usual definition, replacing the current one or something
else ?

cheers,

David


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