[Numpy-discussion] calcul of phase (dividing by 0)

Jean-Luc Menut jeanluc.menut at free.fr
Thu Feb 10 06:21:03 CST 2005


Hello,

I'm want to have the modulus and the phase of a fourier transform of 2D 
array, so I use the numarray FFT to compute the FT of the array (let's 
call it ff) and I use abs(ff) for the modulus and atan(ff.imag/ff.real) 
for the phase.

My problem comes when ff.real = 0, I have either inf or nan as result 
(which is perfectly good and useful). I looking for a function which 
replace atan(ff.imag/ff.real) by 0 when ff.real is 0.

I'm currently using a loop, and I think it's not very good (I call this 
function very often). Since the determination of the phase is something 
really useful and often used, I think there is probably a lot of people 
who had the same problem.

So what solutions do you use?

Thanks,

Jean-Luc Menut




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