[Numpy-discussion] FFT of 2D array along last axis
Brad Buran
bburan at alum.mit.edu
Wed Nov 12 14:24:39 EST 2014
So it seems that the error only occurs in np.fft.rfft (not np.fft.fft).
The following code:
import numpy as np
r = np.random.RandomState(seed=0)
z = r.randn(2**14).reshape((2, -1))
print(np.abs(np.fft.rfft(z)[0])[:5])
print(np.abs(np.fft.rfft(z[0]))[:5])
Prints out on a Windows 7 with Anaconda 64-bit:
[ 94.22136166 149.3181169 145.77500588 177.39556729 172.05616019]
[ 128.55889109 77.35670747 69.63121452 109.06772033 66.22919485]
Prints out on a Ubuntu box:
[ 128.55889109 77.35670747 69.63121452 109.06772033 66.22919485]
[ 128.55889109 77.35670747 69.63121452 109.06772033 66.22919485]
On a Windows 7 with Python(x,y):
[ 128.55889109 77.35670747 69.63121452 109.06772033 66.22919485]
[ 128.55889109 77.35670747 69.63121452 109.06772033 66.22919485]
Brad
On Thu, Nov 6, 2014 at 3:28 PM, Stefan van der Walt <stefan at sun.ac.za>
wrote:
> Hi Brad
>
> On 2014-11-07 00:51:02, Brad Buran <bburan at alum.mit.edu> wrote:
> > On Windows 7 using Anaconda with numpy 1.9.1 I get False (indicating that
> > the FFT is not treating each row separately). When I test on a Ubuntu
> box
> > using numpy 1.9.1 I get True. Is this expected behavior? If I
> understand
> > the documentation correctly, the FFT on each row should be independent
> > (i.e. the result should not be influenced by the other rows).
>
> The results should be the same. As an additional test, can you check:
>
> np.testing.assert_array_almost_equal(np.fft.fft(z, axis=-1)[0],
> np.fft.fft(z[0]))
>
> Thanks
> Stéfan
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