# Double definite integral (Fourier transform)

#### secret2

I don't know if this question should be posted here, but I'll give it a shot anyways.

I am trying to find f(x,y), which can be obtain by doing the backward Fourier integral to F(\omega_x, \omega_y). I have 2 questions.

1. Is there any Fortran code that could evaluate the (numerical) Fourier integral?

2. Since the function f(x,y) is 2-dimensional, we have to do a double integral. Suppose that we evaluate first the x-integral. I have a polynimial in the denominator, but the roots of the polynomial will be functions of y. Then, how can I tell if the (simple) poles are in the upper half plane or not?

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#### DrClaude

Mentor
For the FFT, I generally recommend FFTW.

Alternatively, GSL includes FFT routines.

Another very good implementation (including a version in Fortran), which may be easier to use, is the one by Ooura.

"Double definite integral (Fourier transform)"

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