On Mon, Oct 13, 2008 at 22:36, Collin Day <dcday137@gmail.com> wrote:

Hi all,

I have looked around, but can't seem to find an answer. I have been trying the following (according to the Getting started page - http://www.scipy.org/Getting_Started)

from scipy import * a=zeros(1000) a[:100]=1 b=fft(a)

plot(abs(b))

and I get what you would expect - the abs. value of a sinc function

rect(x) ->F-> sinc(Frequency)

now, if I try the Scipy.fftpack

import scipy.fftapck as S

c=S.fft(a)

figure()

plot(abs(c))

I get something I would expect if I did a FFT on a sine function (kind of like dual spikes equally spaced)

Can you show us the plots? I don't see a difference.

I do see there is a difference in the packing or how the fft output is represented. How do you plot the data from fftpack so that it looks correct? Should I even bother?

Typically, I will use fftfreq() to get the "X" values in packed form and then use fftshift() on both X and Y to "unpack" the arrays. -- Robert Kern "I have come to believe that the whole world is an enigma, a harmless enigma that is made terrible by our own mad attempt to interpret it as though it had an underlying truth." -- Umberto Eco