[SciPy-user] Numpy/Scipy rfft transformations do not match?

Michael Cohen mcohen@caltech....
Sat Feb 28 22:53:40 CST 2009


Hi all,
Relatively new Scipy/numpy user.
I have been trying to switch from numpy.fft.rfft calls to 
scipy.fftpack.rfft calls in order to make use of fftw3, but I find that 
the array sizes are different.

With numpy, the size of the resulting array is n/2+1 where n is the size 
of the original array.  With scipy, the array has length n.
Additionally, scipy takes twice as long to compute the fft as numpy, 
presumably because it is computing twice as many values.
Is there a reason for this discrepancy?  What do I need to call from 
scipy to make the calls match?

Additionally, how do I check in a compiled & installed copy of scipy 
whether it is using fftw or its own fftpack routines?

Regards,
Michael


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