How to set sampling frequency as cycle per year??

How to set sampling frequency as cycle per year??

[Azzi Abdelmalek]

Frequency of what?

Answer 1

[Wayne King]

It depends on the time between your data samples. What is the sampling interval? Were your data acquired at a rate of 1 sample per year, then you just set Fs = 1. If the time interval between samples is 6 months, then you set the sampling rate to 2 (for 2 samples per year).

For example, the time between the sunspot number data is 1 year, so it's one sample per year

   load sunspot.dat
   relNums=sunspot(:,2);
   [pxx,f] = periodogram(relNums,[],[],1);
   plot(f,10*log10(pxx))
   xlabel('Cycles/Year'); ylabel('dB');
   title('Periodogram of Relative Sunspot Number Data');

So I just set the sampling frequency to be 1 and the output of periodogram is in cycles/year.

If the sampling interval is one month, one month between samples, then the sampling frequency would be 12 to yield cycles/year

[Chris Martin]

I also need to know the spectral index of the spectrum how can I get it please help me

[Wayne King]

I answered you in your other post.