[SciPy-user] FFT speed ?
Samuel GARCIA
sgarcia at olfac.univ-lyon1.fr
Thu Feb 8 04:06:07 EST 2007
Thanks all,
for fast and efficient answers.
Zeros padding was really my solution.
Sam
Scott Ransom wrote:
> On Wed, Feb 07, 2007 at 04:39:21PM +0200, Stefan van der Walt wrote:
>
>> On Wed, Feb 07, 2007 at 03:18:19PM +0100, Samuel GARCIA wrote:
>>
>>> yes I was thinking of doing something like that but
>>> fft(a,pow(2,18)).shape is of course 262144 (2**18)
>>> and when I use ifft after that The length of my signal have changed I have an
>>> interpolated signal ... new problem for me ...
>>>
>> An interpolated signal?
>>
>
> Padding a time series gives you an interpolated (actually, the
> term often used is "oversampled" Fourier spectrum).
>
> Scott
>
>
>> In [19]: N.real(N.fft.ifft(N.fft.fft(N.arange(11),16)))
>> Out[19]:
>> array([ 0., 1., 2., 3., 4., 5., 6., 7., 8., 9., 10.,
>> -0., 0., 0., 0., 0.])
>>
>> Padding in the Fourier-domain, on the other hand:
>>
>> In [20]: N.real(N.fft.ifft(N.fft.fft(N.arange(11)),16))
>> Out[20]:
>> array([ 0. , 2.10035464, 3.04455839, 1.35780382, 3.23688237,
>> 3.12291155, 2.35790278, 4.12133152, 3.4375 , 3.29213721,
>> 5.00323313, 3.69035768, 4.32561763, 5.98165513, 3.3443057 ,
>> 6.58344845])
>>
>>
>> Cheers
>> Stéfan
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>>
>
>
--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Samuel Garcia
Universite Claude Bernard LYON 1
CNRS - UMR5020, Laboratoire des Neurosciences et Systemes Sensoriels
50, avenue Tony Garnier
69366 LYON Cedex 07
FRANCE
Tél : 04 37 28 74 64
Fax : 04 37 28 76 01
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