stem function and fft
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i used stem function to convert a continuous signal to discrete signal.
and then i want the discrete function to get the fast Fourier transform of it.
stem return a vertical lines only so what should i do with this vertical lines???
I hope that my question was clear.
Thanks,
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Wayne King
am 16 Dez. 2011
Hi Eman, stem() is not converting the continuous signal to discrete time. stem() just plots. If you have the sequence (vector) in MATLAB, then it is already a discrete-time sequence.
You want to operate on the vector with the function fft()
% an example
x = cos(pi/4*(0:95));
stem(x);
% now obtain the discrete Fourier transform
xdft = fft(x);
stem(abs(xdft));
2 Kommentare
Wayne King
am 16 Dez. 2011
The discrete Fourier transform of a vector is (in general) complex-valued, so you want to plot either the magnitudes (abs()), or the phases (angle() )
In the simple example I gave you, the imaginary parts are all zero, but that is not going to be the case with any real-world signal
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