[SciPy-user] Using fftpack.diff

Neilen Marais nmarais at sun.ac.za
Tue Dec 5 03:36:13 CST 2006


I'm trying to get the DFT of the derivative of a real valued periodic
signal. If I have the time domain
signal in ts (where one period is stored in ts), I do:

fs = scipy.fftpack.fft(ts)
dfs = scipy.fftpack.diff(fs)
dts = scipy.fftpack.ifft(dfs)

However dts seems to be almost purely imaginary whereas ts is purely real.
I haven't done DFT related stuff for a while, am I misunderstanding

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but we've lost the magic
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