I am trying to predict time series. I have several samples which consist of measurement of 4 different variables over different time periods, and other measurements over subsequent time periods which I believe is predicted by the 4 variables. I am thinking of using cluster analysis, to confirm that there is a basis for my belief. I therefore need to compare samples of different lengths, to find the distance between them. I am asking for suggestions on how to compute a distance between my samples. I have thought of using the R time series function spectrum on each sample, and comparing the spectrum differences using the ks test function. I have also thought of using the dtw package to determine a difference. I could also interpolate so each sample is the same length, and use shape matching. I would also like to use either regression or a neural network to try to predict my measurements. Is anyone aware of prediction methods which would not require all my samples to be the same length or how I might deal with different length samples? Thank you, Dan [[alternative HTML version deleted]]