I want to ask. I have my data after Fourier transformation in .mat file. I need to get a spectrogram of it.
What function I should to use in Matlab to do it?
spectrogram() function doesn't fit, because it uses signals before Fourier transformation.
Thank you a lot for any help.
Simply put, you can't. Having the Fourier Transform of the entire signal already performed does not allow you to find the spectrogram. Recall that the spectrogram finds the Fourier Transform of local windows whereas what you have found is the Fourier Transform of the entire signal. The spatial locality of the windows is already lost and so you simply can't do what you're asking.
If your data are FFT of entire the signal, you can't plot the spectrogram. In order to get spectrogram, you have to perform Short-time fourier transform of each frame then plot it to a map.
