MATLAB Answers

Info

This question is closed. Reopen it to edit or answer.

Graphical interpretation of magnitude (derived from fft)

1 view (last 30 days)
Pedro Mateus
Pedro Mateus on 4 Mar 2014
Closed: MATLAB Answer Bot on 20 Aug 2021 at 16:49
Hello to all users of Matlab.
I have 20 years of temperature measurements. Twice a day (max and min) with 12 hours between measurements. To understand which frequencies are more pronounced, I applied the following code:
x = detrend(x);
n = length(x);
nfft = 2^nextpow2(n);
Fs = 1/(12*60*60);
f = 0 : Fs/(nfft-1) : Fs/2;
Y = fft(x, nfft);
Y = Y(1:((nfft+1)/2));
Y = Y/(nfft/2);
Ya = abs(Y);
figure(100)
plot(f, Ya); xlabel('Frequency (Hz)'); ylabel('|Y(f)|'); grid on
I get:
The energy is concentrated in the last frequency (Nyquist, if I'm not mistaken). Is there any error in the code? Not the first time I do this, but never for this type of data and with a sample rate (Fs) so small.
Thanks for the help

Answers (0)

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by