-------- Original Message -------- Subject: Re: Problem with relative warp Date: Fri, 9 Dec 2011 02:41:37 -0500 From: Carmelo Fruciano <[email protected]> To: [email protected] morphmet <[email protected]> ha scritto:
-------- Original Message -------- Subject: Problem with relative warp Date: Sat, 3 Dec 2011 16:42:23 -0500 From: kalpana das <[email protected]> To: [email protected] Dear All, I am facing problem with relative warp analysis.As i have mentioned earlier,I have been working on frogs.I have chosen different number of landmarks to capture snout shape of a frog but still i am not getting different clusters of species in Relative warp plot. I am going with the assumption that snout shape of same species should be similar and it should be cluster together but its not happening. I wanna know the techniques specifically the landmarks i have selected is correct or not.Because i struggled a lot to get results since it is the new technique. It would be a great help if you can tell me where i am going wrong? Waiting for your response.
Dear Kalpana, I think you're not necessarily doing something wrong. Differences between groups (if they ever exist in the first place) might span different directions in the multivariate space than the one you are looking to (I assume you're looking at scatterplot of the first few PC axes). Also, you don't mention if you did some sort of "allometric correction" which might partially explain why you don't see clusters in the first few RW (which, in turn, might represent allometric variation within species). Finally, depending on what you want to study, it might be that PCA is not necessarily the best tool for you (if are looking to discriminate groups other methods might be more suitable). Just my two cents... Carmelo -- Carmelo Fruciano Post-doc - University of Konstanz - Konstanz, Germany Honorary Fellow - University of Catania - Catania, Italy e-mail [email protected] http://www.fruciano.it/research/ ---------------------------------------------------------------- Universita' di Catania - A.P.Se.Ma. Servizio di Posta Elettronica
