# calculate normalised frequency of the below plot

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Venkatkumar M on 12 Aug 2019
Commented: Star Strider on 13 Aug 2019
How to calulate frequency from above graph?
convert normalised frequency(0.03) into frequncy(hz)?
how to do this?

Star Strider on 12 Aug 2019
convert normalised frequency(0.03) into frequncy(hz)?
Multiply the normalised frequency by the Nyquist frequency.
The sampling frequency is 1/(sampling interval). The Nyquist frequency is one-half of the sampling frequency.
Star Strider on 13 Aug 2019
You need to understand the argument list order for the pwelch function.
Try this:
[pxx,f] = pwelch(D2,[],[],[],Fs);
figure
subplot(3,1,1)
plot(f, pxx(:,1))
grid
xlabel('Frequency (Hz)')
ylabel('PSD')
title('Column 1')
subplot(3,1,2)
plot(f, pxx(:,2))
grid
xlabel('Frequency (Hz)')
ylabel('PSD')
title('Column 2')
subplot(3,1,3)
plot(f, pxx(:,3))
grid
xlabel('Frequency (Hz)')
ylabel('PSD')
title('Column 3')
That worked when I ran it.

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