[SciPy-user] Difference between ffts? - plots of what i am getting.

Collin Day dcday137@gmail....
Tue Oct 14 22:38:30 CDT 2008


David Cournapeau <david <at> ar.media.kyoto-u.ac.jp> writes:

> 
> Collin Day wrote:
> > No problem.  Sorry for not replying directly - I get the digests so my
> > mail box remains uncluttered.  Anyway,  I have attached two files.
> > Following are the lines of code I used:
> >   
> 
> Hi Collin,
> 
>     Would it be possible to provide the exact script which produces the
> graph ? One graph looks like a log graph, the other linear, and I can't
> see how it would be possible for both graphs to be produced by the above
> script, even assuming bugs in scipy ?
> 
> Also, to know which fft was used, could you execute the following
> command and give us the result:
> 
> import scipy
> scipy.show_config()
> 
> thanks,
> 
> David
> 
Sure.  The following script will produce the plots:


#!/usr/bin/python

from pylab import *
import scipy as S
import scipy.fftpack as SF

a=zeros(1000)
a[:100]=1
b=S.fft(a)
c=SF.fft(a)
figure(1)
plot(abs(b))
show(1)
figure(2)
plot(abs(c))
show(2)

and scipy was compiled using the FFTW library.  The only thing I can thinkk of
would be to recompile not using it.

Hope that helps.  I really hope I have not done something stupid and missed it.
 Anyway, thanks again everyone!

-C





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