Automatic Complex Conjugate in ftt

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Ha Oe 2019-11-26

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https://ww2.mathworks.cn/matlabcentral/answers/493355-automatic-complex-conjugate-in-ftt

评论： Ha Oe 2019-11-26

So I am computing the fft of an array containing vectors. The documentation says that the fft treats each collumn as a vector and computes the fft of each collumn. This means that the following should be the same:

% F1 and F2 should be equal
data = rand(4,100)
F1 = fft(data')' ; % F1
F2 = zeros(size(data)) ;
for n = 1:4
    F2(n,:) = fft(data(n,:)) ;  % F2
end

But they are not equal. In fact, F2 is the complex conjugate of F1. Does anyone know why this is this happening?

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Answer 1

David Goodmanson 2019-11-26

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https://ww2.mathworks.cn/matlabcentral/answers/493355-automatic-complex-conjugate-in-ftt#answer_403498

Hello Ha Oe

the quote command is not just the transpose, it's the complex conjugate transpose (Hermetian conjugate). For the straight transpose, use .' (dot quote).