title: Units of frequency when using FFT in NumPy
body: <p>I am using the FFT function in NumPy to do some signal processing. I have array called <code>signal</code>
  which has one data point for each hour and has a total of 576 data points. I use the following code on <code>signal</code> to look at its fourier transform.</p>
  
  <pre><code>t = len(signal)
  ft = fft(signal,n=t)
  mgft=abs(ft)
  plot(mgft[0:t/2+1])
  </code></pre>
  
  <p>I see two peaks but I am unsure as to what the units of the x axis are i.e., how they map onto hours? Any help would be appreciated.</p>