I am in the midst of doing analysis for my dissertation and would really appreciate some help. I am exploring the relationships between stable carbon and nitrogen isotope ratios (continuous variables) and various predictors such as latitude, longitude, month, and year. I then want to use the relationships to see if the isotope ratios on their own can predict the location from which they came. So far I have done simple linear regression between each ratio and each predictor. I also did a series of ANOVAs. I followed these with discriminant function analyses and had fairly decent results. However, I have been advise to alter my approach and "test for non-linear relationships, either with polynomial regression or GAMs" and to classify using classification and regression trees rather than DFA. I am currently using the SPSS 15.0 grad pack and can't see to determine if these analyses are possible in my package. If they are, I don't know how to execute them. HELP! Thanks in advance!

-- Briana H. Witteveen Doctoral Candidate

University of Alaska Fairbanks University of Central Florida Physiological Ecology and Bioenergetics Lab 118 Trident Way Kodiak, AK 99615 Office: (907) 486-1514 Mobile: (907) 942-2733

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