Mercurial > repos > public > sbplib
comparison four.m @ 598:f6ada1719420 feature/grids
Add functions for calculating fourier transforms
| author | Jonatan Werpers <jonatan@werpers.com> |
|---|---|
| date | Thu, 14 Sep 2017 14:30:57 +0200 |
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| children |
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| 586:97b9a0023d38 | 598:f6ada1719420 |
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| 1 % four returns the fourier transform u_hat of the function u and the frequencies w | |
| 2 function [w, u_hat] = four(x, u) | |
| 3 u_hat = fft(u); | |
| 4 | |
| 5 N = length(x); | |
| 6 L = x(end) - x(1); | |
| 7 | |
| 8 k = shift_k(0:N-1); | |
| 9 | |
| 10 u_hat = fftshift(u_hat); | |
| 11 | |
| 12 dw = 2*pi/L; | |
| 13 w = dw*k; | |
| 14 end | |
| 15 | |
| 16 function k_shifted = shift_k(k) | |
| 17 N = length(k); | |
| 18 k_shifted = [-floor(N/2):-1, 0, 1:ceil(N/2)-1]; | |
| 19 end |