title: Fast Fourier Transform for radial forces in Python
body: <p>First of all I want to say that I am very new in this and some help it would be welcome. I want to calculate fft for radial forces and something I'm missing. Until now I have something like this:</p>
  
  <pre><code>t=np.arange(145)
  sp=np.fft.fft(radial_force)
  freq=np.fft.fftfreq(t.shape[-1])
  pl.plot(freq, radial_force.real, freq,radial_force.imag)
  pl.show()
  </code></pre>
  
  <p>I get really big values and I don't know why. Any hint would be helpful.
  Thank you in advance !</p>