How does the command: real(ifft(fftshift(Y))*N) operate?
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Hello, I am interested in knowing how this form of the inverse FFT command which is
real(ifft(fftshift(Y))*N)
works and its complexity for a vector Y of N sample points, because I have seen some basic ifft commands as seen here but this one seems to involve ifft and fft together.
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Matt J
2021년 4월 20일
편집: Matt J
2021년 4월 20일
All of those oeprations are O(N) except for the IFFT which is O(Nlog(N)). So the chain of operations is O(Nlog(N)) overall.It would be slightly more efficient to re-implement it as,
N*real(ifft(fftshift(Y)))
since then the multiplication with N only needs to operate on real numbers.
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Matt J
2021년 4월 20일
but this one seems to involve ifft and fft together.
No, it doesn't. But the FFT is also O(log(N)), so including an FFT step wouldn't increase the complexity either.
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