How do find the frequency from a FFT graph?

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Aidil AA 2018-10-9

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评论： Aidil AA 2018-10-10

IMG-20180930-WA0004.jpg

Hi guys, I have an audiowave file, I have gotten the time domain and the fft graph. My question what is the next step to find the frequency from the fft graph? Thanks.

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KALYAN ACHARJYA 2018-10-9

Check here it may be helpful.

KSSV 2018-10-9

YOu can click using datatips...or use findpeaks. Or +sort_ the x-axis and pick the respective required y-axes i.e frequencies.

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David Goodmanson 2018-10-9

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Hi Aidil,

if there are N points in the data array, then the frequency array consists of N points with spacing fs/N. The following example uses fftshift to put zero frequency at the center of the array. It's slightly different for N even or N odd.

data_fft = fftshift(fft(data))
N = length(data);
if rem(N,2) == 0
    f = (-N/2:N/2-1)      *(fs/N)         % N is even
else
    f = (-(N-1)/2:(N-1)/2)*(fs/N)
end
plot(f,abs(data_fft))