This is more of a data analysis question than a mathematics question so feel free to move it to wherever you think it is most likely to be answered. I have some time series data that looks (just by eye) like it should have several peaks in its power spectrum. However, when I compute the power spectrum, the function I get is nearly identically zero. It has a very large power value for the first frequency point and then 0 everywhere else. Has anyone else encountered this problem? Any ideas what could be happening? I'm pretty sure that the method I am using to calculate the power spectrum is (nearly) good since I can get good results on sine waves and the like. It just doesn't seem to work on any actual data.