Find the frequency vector using pwelch function

Hi all,

I have a seismic signal recorded at 200 Hz. I want to use the pwelch (using a hanning window) to find the spectra but for some reason the frequency vector is wrong (or, altenratively, I don't intepert it correclty).

For example, with 200 Hz sampling frequency, I am supposed to observe frequency range from 0 to 100 Hz in the x axis using the command:

plot(f,10*log10(pxx))

I would appreciate your help!

(please se attached seismic vector)

Thanks!

Ron

Answer 1

[Hiro Yoshino]

Did you pay attention to the Normalized Frequency?

The Power Spectral Density is estimated on the frequency. Its unit is Rad/sample.