Dear Morphometricians, I am preparing to do a discriminant analysis on a genus of sharks to see if I get species clustering. The first consideration is that most sharks are sexually dimorphic, and extremely so for the genus I am investigating, so I am expecting to see more groupings than there are species. There is also a considerable amount of ontogenetic change. I have a considerable data set in terms of variables (about 100 measurements for each individual), however for most species (which are extremely rare) I have a sample size of only 4 individuals and for a few species n=20+. Quite a number of the measurements are additive, however the majority of the measurements are non-additive.
First question: will the non-additive measurements 'swamp' the effects of the additive measurements? Secondly, if the additive measurements are not 'swamped' by the non-additive measurements, what is the best approach to removing measurements from the analysis? For example, if I have: total length (TL) = head length (HL) + body length (BL) + tail length (tL) then is removal of TL sufficient, or do I need to remove HL or BL or tL, or do I need to remove TL plus one of the other measurements, or can I retain TL and just remove one of the additive measurements?? Thirdly, how much information am I losing in removing a measurement besides TL, because any one of HL, BL or tL may be a major diagnostic feature between species, between sexes, or even between ontogenetic stages?? Any comments will be appreciated. Thanks, Brett *************************************************** Mr Brett Human (PhD candidate) Shark Research Center South African Museum PO Box 61 Cape Town 8000 South Africa ph: 27 21 481 3856 fax: 27 21 481 3993 or email: [EMAIL PROTECTED] ph: 27 21 406 6430 fax: 27 21 448 8350 **************************************************** Visit Iziko Museums of Cape Town on the web:- http://www.museums.org.za/iziko. ********************************************************************* This E-mail contains confidential information for the addressee only. If you are not the intended recipient, please notify the sender and delete it immediately. Any use, disclosure, distribution or copying of this communication, by persons or entities other than the recipient is prohibited. No binding contract will result from this e-mail until such time as a written document is signed on behalf of Iziko Museums of Cape Town. Iziko Museums of Cape Town cannot accept any responsibility for the completeness or accuracy of this message or guarantee that the communication is free of errors, virus, interception or interference. The views and opinions expressed in this e-mail are those of the sender unless clearly stated as being those of Iziko Museums of Cape Town. Thank You ********************************************************************* == Replies will be sent to list. For more information see http://life.bio.sunysb.edu/morph/morphmet.html.
