y<-ts(x, frequency=1/15) spec.pgram(y, log="no") There is high power in the very low frequency range for the data set of continuous dissolved oxygen on which I am preforming this analysis. This is the seasonal trend due to temperature (and all things that are associated- photosynthesis, respiration, and anything else on which the doubling of a reaction rate ever ten degrees celcius would act). I would like to make this low frequency spike zero and then inverse fourier transform to get the "filtered" signal. spec.pgram spits out a matrix z<-spec.pgram(y, log="no") print(z) spec, frequency, and phase are returned. They are not matched up and I would like to take out the frequency and its associated spectrum in the range of 0-6.53*10^6. Any suggestions? thanks Stephen -- Let's not spend our time and resources thinking about things that are so little or so large that all they really do for us is puff us up and make us feel like gods. We are mammals, and have not exhausted the annoying little problems of being mammals. -K. Mullis