[Scipy-tickets] [SciPy] #1232: Support fft normalization once added to numpy
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Thu Jul 15 08:25:08 CDT 2010
#1232: Support fft normalization once added to numpy
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Reporter: dgoldsmith | Owner: somebody
Type: enhancement | Status: new
Priority: normal | Milestone: 0.9.0
Component: Other | Version: 0.7.0
Keywords: fft normalization keyword unitary |
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Comment(by charris):
Yes, the pair needs to be normalized, but the divide by N normalization is
often not the right one. I usually normalize the transforms by the spacing
of the samples, seconds or centimeters in the forward case, hz or 1/cm in
the reverse case. This deals properly with resampling and gives everything
useful units. The usual normalization corresponds to taking the spacing of
the original data set to be 1 and doesn't work properly if one wants to
interpolate the original data by extending the transform with zeros. This
normalization also preserves the sum of squares if one multiplies the sums
by the respective sample spacings so they look like integrals. So I don't
want numpy doing my normalization, numpy gets it wrong for many cases and
it is a hassle to undo the damage. Better would be to add a keyword for a
scaling factor. FFTW got this aspect right.
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Ticket URL: <http://projects.scipy.org/scipy/ticket/1232#comment:10>
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