how to know the frequency on the fft plot
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if I'm doing fft of my signal, and ploting it
plot(abs(fft(x)).
Now how do I match an index on the graph to a specific frequency? I came to the formula of -
f = (FPS/N)*(i-1)
f - the frequency I am looking for
FPS - the Frames Per Second of the original signal in the time domain
N - total number to recorded frames in the time domain
i - index on x-axis on my abs(fft(x)) plot.
does that correct?
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Walter Roberson
2015-7-31
Yes, except that it only works for the first half of the fft.
See http://www.mathworks.com/help/matlab/ref/fft.html and notice how they only plot the first half with a formula for "f" that works out the same as the one you have.
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