urgent power spectacular density

[horizon12]

hello

I did my a Power spectral density and my sampling frequency is at 1000Hz so I suppose to get the range from 0 to 500Hz

but the thing my PSD is symmetric around 250 Hz


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**broken link removed**


so is that correct ?

if not can tell me what is the wrong ??

tanks a lot.

 

[JoannesPaulus]

you need to shift the spectrum and plot half the data. Try "help fftshift".