Scipy/Numpy FFT Frequency Analysis

Question

I\'m looking for how to turn the frequency axis in a fft (taken via scipy.fftpack.fftfreq) into a frequency in Hertz, rather than bins or fractional bins.

I tried to

Answer 1

Your equation is messed up.

fs = 33.33
df1 = 2*pi * (2.0/fs)
df2 = 2*pi * (5.0/fs)
x = [10*sin(n*df1) + 5*sin(n*df2) + 2*random.random() for n in range(4000)]

This gives you 4000 samples of your function, sampled at 33.33 Hz, representing 120 seconds of data.

Now take your FFT. Bin 0 will hold the DC result. Bin 1 will be 33.33, bin 2 will be 66.66, etc..

Edit: I forget to mention that, since your sampling rate is 33.33 Hz, the maximum frequency that can be represented will be fs/2, or 16.665 Hz.