Wrong answer using " fft (ifft ( vector )) "

1 次查看（过去 30 天）
Ahmed
Ahmed 2014-12-6
回答： Andrew Newell 2014-12-6
For my following vector when I use fft (ifft ( vector )) the answer is almost same as vector but at 129th position its different whereas the answer should be same as vector. Please help.
vector=
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fft (ifft ( vector ))=
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回答（1 个）

Andrew Newell
Andrew Newell 2014-12-6
The FFT algorithm is a numeric algorithm, with the inevitable round-off errors (see Floating point numbers), so you can't expect exact agreement.
Try the command
max(abs(vector-fft(ifft(vector))))
You'll find the maximum difference is about 1.8e-10.

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