Problem with ifftn and ifftshift??
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Hi there I was wondering if someone could help me. I am using the fftn fftshift functions as part of my alogrithm;
tmp = fftn(MAT); Adash = fftshift(tmp);
Adashup=ifftshift(Adash);
Adashup2new = ifftn(Adashup);
However, When I took everything else out and left these in as a tester I noticed that instead of the above taking me back to the original MAT, it alters the numbers quite a lot. What am I doing wrong?? Example original file MAT has a min of 0 and a max of 1.0856, however the file Adashup2new has a min of -6.792 and a max of 1.0856
2 件のコメント
Mehri Mehrnia
2023 年 10 月 14 日
why we should use fftshit?when I dont use fftshit, scale is good and untouched
Walter Roberson
2023 年 10 月 14 日
fft() returns back the 2-sided fft. By convention, the order of frequency bins returns back from fft() of real input signals is like
0, 1, 2, 3, 4, ... n-1, n, conj(-n), conj(-(n-1)), ... conj(-(4)), conj(-(3)), conj(-(2)), conj(-1)
but people often prefer to visualize it in the order
conj(-(n-1)), ... conj(-(4)), conj(-(3)), conj(-(2)), conj(-1), 0, 1, 2, 3, 4, ... n-1, n
The change is not mathematically significant: it is just easier for people to look at the plots.
採用された回答
Nitin
2013 年 6 月 26 日
Sounds like Imaginary components are there due to round off errors, try extracting the real part
f = real(ifft2(F));
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