If I compute the DFT using the definition given on Wikipedia, real components relate directly to cosine amplitudes and imaginary components relate directly to sine amplitudes.
I.e.
dft(sin(t))= [0, 0-0.5i, 0, 0, 0, 0, 0, 0+0.5i]
where
t=linspace(2*pi/8,2*pi,8);
but using the fft function:
fft(sin(t))/8= [0, 0.3536-0.3536i, 0, 0, 0, 0, 0, 0.3536+0.3536i]
The magnitudes are equal but I can no longer seperate sine and cosine components with FFT. Is there any way I can pre-treat my data so I can use FFT to give the same outputs as DFT?
Best Answer