[SciPy-Dev] fftpack.convolve.convolve
Clemens Novak
clemens@familie-novak....
Fri Aug 16 05:36:51 CDT 2013
Hi,
I've been working on extending the fftpack tutorial page (you can see
the current status here:
https://github.com/ClemensFMN/scipy/blob/tut_fft/doc/source/tutorial/fftpack.rst
) and I stumbled across the function fftpack.convolve.convolve .
Sorry the blunt question, but what does this function do? From the name
I'd assume that it calculates the convolution of two sequences (as
convolve in scipy.signal does) using the fft (since it is part of
fftpack), but appearently it doesn't:
import numpy as np
import scipy.fftpack.convolve as conv
import scipy as sp
import scipy.signal as sig
x = np.array([1.0, 0.0, 0.0])
h = np.array([1.0, 2.0, 3.0])
y1 = conv.convolve(x, h)
[ 5. -1. -1.]
y2 = sig.convolve(x, h)
[ 1. 2. 3. 0. 0.]
y3 = sp.ifft(sp.fft(x) * sp.fft(h))
[ 1.+0.j 2.+0.j 3.+0.j]
Does the function extend its first and/or second argument to a periodic
sequence and perform then the convolution (I tried some ideas but that
didn'twork either)? It would be great if someone could please provide
some insight...
Regards - Clemens
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