# [SciPy-user] FFT indexes with zero-padding

Forrest Sheng Bao forrest.bao@gmail....
Mon Jan 19 22:18:56 CST 2009

```Hi,

I am thinking about a question regarding the indexes of FFT result with

Suppose there is no zero-padding that the length of signal is a power of 2,
like 4096. Then the index corresponding to frequency f should be f/fs*N,
where fs is the sampling rate and N is the number of points.

But, what if the length of signal is not a power of 2? Like 5000? How does
Scipy.signal module handle this?

For example, I have 5000 samples and am doing 5000-point FFT. The sampling
rate is 200Hz. Is the index for 2 Hz still 2 / 200* 5000 = 50?

Cheers,
Forrest

--
Forrest Sheng Bao, B.S. EE
Ph.D. student/Teaching Assistant, Dept. of Computer Science
M.Sc. student/Research Assistant, Dept. of Electrical & Computer Engineering
Rm 115, Experimental Sciences Building
Texas Tech University, Lubbock, Texas, USA
http://narnia.cs.ttu.edu
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