[Numpy-discussion] rfft different in numpy vs scipy
Andrew Jaffe
a.h.jaffe at gmail.com
Thu Sep 7 17:46:15 CDT 2006
Hi all,
It seems that scipy and numpy define rfft differently.
numpy returns n/2+1 complex numbers (so the first and last numbers are
actually real) with the frequencies equivalent to the positive part of
the fftfreq, whereas scipy returns n real numbers with the frequencies
as in rfftfreq (i.e., two real numbers at the same frequency, except for
the highest and lowest) [All of the above for even n; but the difference
between numpy and scipy remains for odd n.]
I think the numpy behavior makes more sense, as it doesn't require any
unpacking after the fact, at the expense of a tiny amount of wasted
space. But would this in fact require scipy doing extra work from
whatever the 'native' real_fft (fftw, I assume) produces?
Anyone else have an opinion?
Andrew
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