Asked by Alex Vasin
on 11 Apr 2019

I have all the |C_n|^2 and need to plot bars which represent the energy at intervals of w (angular frequency).

I guess this would be a bar graph but I want lines instead (which I can label if possible).

Something like this but only need labels for the x axis:

https://www.oreilly.com/library/view/elegant-scipy/9781491922927/assets/elsp_0402.png

Thanks

Answer by Clay Swackhamer
on 11 Apr 2019

Accepted Answer

This might have what you are looking for https://www.mathworks.com/help/matlab/ref/fft.html

You could transform the data from output space (voltage vs time or similar) into a frequency spectrum (power vs frequency or similar) and then plot that.

Alex Vasin
on 11 Apr 2019

dpb
on 11 Apr 2019

Alex...use the "COMMENT" button for clarifications, comments...they're answers to questions about the original question, yes, but not an Answer to your original question -- dpb

C_n is the complex Fourier coefficient. I need to do a complex power spectrum. So the x-axis is w (angular fequency) at intervals of pi, since w_0=pi. And at each of those frequencies I want a line going up that represents the energy of the freqrency (calculated as |C_n|^2). As I said, I only need to know how to plot the graph. I do not need help with computations.

dpb
on 11 Apr 2019

Look at the example of computing PSD at

doc fft

It shows how to compute the frequency against which to plot the PSD and plots it with plot which is the normal thing.

You would simply call one of the other routines in place of plot to try something different. I've never done a PSD by either, so no idea how well it will actually work to display the information in a useful format, but you can give it a go... :)

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