[Numpy-discussion] FFT usage / consistency

[Felix Richter]

I learned a few things in the meantime:

In my installation, NumPy uses fftpack_lite while SciPy uses FFTW3. There are 
more test cases in SciPy which all pass. So I am confirmed my problem is a 
pure usage problem.
One thing I was confused about is the fact that even if I calculate the 
function over a certain interval, I cannot tell FFT which interval this is, 
it will instead assume [0...n]. So actually I did not transform a Lorentz 
function centered at zero but rather centered at 500.
Unfortunately, this solves only half of my problem, because I still cannot 
reproduce the exact FT. I'll ask for that on the SciPy list, this now seems 
more appropriate.