I am comparing the efficacy of two filtering techniques on a simulated time series that has random and systematic errors. As the data is simulated, I know the frequencies and amplitudes that generate the systematic noise. I'm looking for a way to compare the techniques in a simulation framework - i.e., I will generate many instances of the time series varying the parameters, perform the filtering, and test the filters against the input. I have started doing this by combining the filtered series and the systematic noise as a single time series using ts.union() and then running spectrum() and comparing the coherencies of the filters against the systematic noise at the right frequencies. This seems to work but it is simplistic. Can anybody think of a tidy method in R of comparing two time series against a known spectrum to test which one preserves that spectrum better? Best regards, Andy