[Numpy-discussion] Bug in numpy.correlate documentation

Nathaniel Smith njs at pobox.com
Wed Oct 9 16:54:07 EDT 2013

On Wed, Oct 9, 2013 at 7:48 PM, Bernhard Spinnler
<Bernhard.Spinnler at gmx.net> wrote:
> Hi Richard,
> Ah, I searched the list but didn't find those posts before…
> I can easily imagine that correlation is defined differently in different
> disciplines. Both ways are correct and it's just a convention or definition.
> In my field (Digital Communications, Digital Signal Processing) the vast
> majority uses the convention implemented by the code. Here are a few
> examples of prominent text books:
> - Papoulis, "Probaility, Random Variables, and Stochastic Processes",
> McGraw-Hill, 2nd ed.
> - Benvenuto, Cherubini, "Algorithms for Communications Systems and their
> Applications", Wiley.
> - Carlson, "Communication Systems" 4th ed. 2002, McGraw-Hill.
> Last not least, Matlab's xcorr() function behaves exactly like correlate()
> does right now, see
> - http://www.mathworks.de/de/help/signal/ref/xcorr.html
> But, as you say, the most important aspect might be, that most people will
> probably prefer changing the docs instead of changing the code.

Yeah, unless the current behaviour is actually broken or redundant in
some way, we're not going to switch from one perfectly good convention
to another perfectly good convention and break everyone's code in the

The most helpful thing would be if you could file a pull request that
just changes the docstring to what you think it should be. Extra bonus
points if it points out that there is another definition some people
might be expecting instead, and explains how those people can use the
existing functions to get what they want. :-)


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