Hi all, and thank you for reading/responding to my thread.I have a problem which involves time series and its power spectra. Some background: I have an 10.000xN matrix(called matr) whose columns are individual time series with real data values and I want to plot their power spectra against frequency.These time series where generated by an iterative map which involved a sin function with omega=0.1. Plotting freq versus power I might be able to see if any harmonics are present. Below are the steps I take in Matlab: y=fft(matr) % get the fourier transform of the matrix y=(abs(y)).^2 %this is the power spectra Is the above right? Also I'm puzzled as to what frequency range I should use. Does freq=(0:10000-1)/10000 seems right? Any suggestions? Thank you all