FFT Power units for a time series?
1 view (last 30 days)
Show older comments
Hello,
I have a time series of the concentration of a gas (in parts per million, or ppm) in the atmosphere with time over several years. The concentration with time approximates a sinusoid with frequency 2*pi/365 days, but it also has a 6-monthly term (first harmonic) of frequency 4*pi/365 days. I've run an fft of this time series, which comes out showing peaks at 1-year and 6-month frequencies. My only issue is that I'm not sure what the units on the y axis ("power") are. Can anyone help with this?
Thanks
0 Comments
Answers (1)
Jonathan LeSage
on 17 Oct 2013
Edited: Jonathan LeSage
on 17 Oct 2013
Commonly, you can express the y-axis units in terms of power/frequency. If you use the logarithmic decibel scale, the units of your y-axis would be dB/(Hz or 1/days... what ever your time scale is).
This documentation article might help clarify things: http://www.mathworks.com/help/signal/ug/psd-estimate-using-fft.html?BB=1
0 Comments
See Also
Categories
Find more on Fourier Analysis and Filtering in Help Center and File Exchange
Products
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!