simple fft code problem

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ayman osama
ayman osama 2012-12-3
x=rand(1,8);
for k=1:8
for m=1:8
l(m)=x(m)*exp(-i*2*pi*k*m/8);
end
X(k)=sum(l);
end
X=X
I used this code to implement the fast Fourier transform but it didn't work. Is there any help?
  2 个评论
Matt J
Matt J 2012-12-3
This is closer to the DFT than the FFT.
Azzi Abdelmalek
Azzi Abdelmalek 2012-12-3
It's right, this is 'nt FFT algorithm, but the FFT is just a faster way to calculate a DFT. the result will be the same

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Azzi Abdelmalek
Azzi Abdelmalek 2012-12-3
编辑：Azzi Abdelmalek 2012-12-3
%k and m start at 0
x=rand(1,8);
for k=0:7
for m=0:7
l(m+1)=x(m+1)*exp(-i*k*m*pi/4);
end
X(k+1)=sum(l);
end
%or
R=exp(-i*2*pi/8)
k=0:7;
XX=exp(-i*pi/4).^(k'*k)*x'
Remark: for big array, you must use FFT algorithm
  2 个评论
Azzi Abdelmalek
Azzi Abdelmalek 2012-12-3
compare the result with fft(x), it's the same
ayman osama
ayman osama 2012-12-3
thank u for help

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