[Numpy-discussion] Problem with correlate

[Charles R Harris]

On Tue, Jun 2, 2009 at 1:16 PM, rob steed <rjsteed at talk21.com> wrote:

>
> I also think that the conjugate should be taken. I spent the last few weeks
> using correlate to experiment with
> signal processing and I got strange results until I realised that I had to
> manually take the conjugate. It
> would also be good if the function did it since applying the conjugate to
> the wrong sequence yields the
> complex conjugate of the correlation.
>
> Who would want to use the correlation without the conjugate, if someone is
> only using real values it won't
> affect them, if they are using complex values they probably want to
> conjugate.
>
> One function that does depend on correlate though is convolution! Changes
> made to correlate will
> affect it! but I have understand that a new function acorrelate is being
> created instead of changing
> correlate?
>
> Otherwise I've never used matlab but it does seem like xcorr has some good
> features. The modes
> 'same' and 'valid' were initially quite confusing especially as the default
> is 'valid', meaning that autocorrelations
> lead to a single value by default!
>
> I also think that having weighting options would be good.  I now understand
> the complexities of the various
> weightings that can be applied to the correlation i.e. biased vs unbiased
> but I think that having correlate
> include these options might prompt users to investigate which one they
> really needed. Correlate seemed
> so simple when I first used it but it took me ages to realise that these
> are choices to be made.
>

I wonder if xcorrelate would be a better name than acorrelate?

Chuck
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