FFT - Return vector and Frequency display

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Anmol Pardeshi
Anmol Pardeshi 2019-4-15
编辑： kholoud salameh 2019-5-31
fft function - it returns a vector, same length as the signal, but if we plot the abs(signalFFT), the x axis does not quite depict the exact frequency, although it is very close. I would want to know how does this fft function works, what it exacts returns & how and what do I do to fix this.

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kholoud salameh
kholoud salameh 2019-5-31
编辑：kholoud salameh 2019-5-31
hi , if you try this code :
f = abs(fft(y));
plot(f)
it will plot y by sample at x-axis which is the length of f ! to get y by the exact frequency try this one :
f = abs(fft(y)); % calculate the magnitude of fft
index = 1:length(f);
index = index ./length(f) ;
index = index * fs ;
figure
plot(index,f); % plot frequency spectrum

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