Zero mean values but still dominant frequency is zero
5 vues (au cours des 30 derniers jours)
Afficher commentaires plus anciens
Hello,
I have a series of numbers and I try to find the dominant frequency using FFT. I know that for the FFT to work properly my series should have a mean equal to zero. However even if I impose the mean to be zero, the dominant frequency still remains zero, which is of no interest. Here is my code(a is the array that consists of the series)
a=detrend(a,0);
Fs=67890;
T=1/Fs;
L=1000;
t=(0:L-1)*T;
Y=fft(a);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
b=P1/max(P1);
When I plot(f,b) I take this image
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/164904/image.jpeg)
which means that zero frequency is still dominant. What am I doing wrong? Or is it impossible to do anything?
0 commentaires
Réponses (1)
Walter Roberson
le 6 Juin 2017
You appear to be plotting on a truncated log scale. 0 does not appear on your x axis. Your peak is somewhere in the range 0 to 70 Hz.
0 commentaires
Voir également
Catégories
En savoir plus sur Fourier Analysis and Filtering dans Help Center et File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!