FFT woes
Brian Kelley
bkelley at wi.mit.edu
Thu Jan 2 17:29:15 CET 2003
Adding to what eric mentioned about taking the log of zero, perhaps it
would be better if you plotted the periodogram of that data. I expect
that your signal might just have a mean of zero. The fft-zero frequency
is the average of the signal.
Since the zero-frequency is dominating and equal to the average of the
signal, the periodogram simply removes this. The non-zero frequencies
show up a lot better.
You will need some way of computing the mean. I use the stats.py
package. You can just google search for this.
def periodogram(vector):
mean = stats.mean(vector)
a = FFT.fft(vector-mean)
N = len(a)
ab = abs(a)
return (ab*ab)/N
Enjoy.
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