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Fast Fourier Transform in MATLAB
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[QUOTE="member 428835, post: 6217027"] Hi PF! I'm following a tutorial in MATLAB, shown here [code] t = 0:.001:.25; x = sin(2*pi*50*t) + sin(2*pi*120*t); y = x + 2*randn(size(t)); Y = fft(y,251); Pyy = Y.*conj(Y)/251; f = 1000/251*(0:127); plot(f,Pyy(1:128)) title('Power spectral density') xlabel('Frequency (Hz)') [/code] I read the documentation but a few things are still unclear, which I'll list for clarity: Line 4: why use the 251 part of the transform? Line 5: Why this rather than, say Norm(Y)? Line 6: so the 1000 is evidently from line 1, the time step? But where is the 251 coming from; looks like it's the time step * end time + 1. Thanks! [/QUOTE]
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Fast Fourier Transform in MATLAB
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