Question on Discrete Cosine Transform FFT

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Matlab Student 2018-10-20

评论： Matlab Student 2018-10-20

Hello Team,

My Matlab code calculate a vector signal. When I plot the signal, it looks like the attached signal1.

After I apply fft, the signal becomes like signal2. It does look correct. Am I right?

Thanks

Bruno Luong 2018-10-20

It seems the graph is

abs(fft(data))

because fft returns complex data when when you plot it without ABS, you get the points in complex plane, and not amplitude vs frequency.

Take a look at the documents of functions PLOT, FFT, FFTSHIFT

Matlab Student 2018-10-20

Thank you Bruno, that was really helpful. Also thanks for the documents you have advised.

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