title: When should I use fftshift(fft(fftshift(x))) and when fft(x)?
body: <p>I am trying to implement an algorithm in python, but I am not sure when I should use <code>fftshift(fft(fftshift(x)))</code> and when only <code>fft(x)</code> (from numpy). Is there a rule of thumb based on the shape of input data?<br>
   I am using <code>fftshift</code> instead of <code>ifftshift</code> due to the even number of values in the vector <code>x</code>.</p>