Dear Brett, If the problem is separating size and shape, then, fortunately, in my edited book titled "Morphometrics- Applications in Biology and Paleontology" (Springer-Verlag, 2004) you will find a chapter that is written by Garcia-Rodriguez et al. They used the Sheared PCA analysis and could successfully separate size and shape as separate components. Although there are more recent techniques for doing that, however, I recommend you to read this chapter for knowing how they could separate size and shape using an excellent and easy manner. Best regards. Ashraf ---------------------------------------------------------------------------- --- Dr. Ashraf M. T. Elewa Associate Professor Geology Department Faculty of Science Minia University Egypt [EMAIL PROTECTED] http://myprofile.cos.com/aelewa ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, May 17, 2004 05:09 ? Subject: size correction & discriminant functions analyses
> Dear morphometrician, > > I have recently reviewed 3 genera of catsharks that display a great deal of morphological conservation within the genera, however, there is also prominent sexual dimorphism present (profoundly so in some species). There is quite a bit of shape variation between juveniles and adults, in one genus in particular, but I think that the shape variation is being obscured by the size component. > > I have a sizeable morphometric data set (# measures >> # taxa & specimens) and have used principal components analysis on the raw data to explore shape variation within each of the genera (not between). The first component was always a general component and accounted for more than 85-90% of the variation in most instances, therefore the bipolar components only contributed relatively little to the overall shape variation resulting in crowded PCA plots. > > The main reference I have used for the analyses to date has been 'Pimental. 1979. Morphometrics. The multivariate analysis of biological data' however, it doesn't deal with size correction. Can anyone suggest a review that deals with size correction, or can I convert my data to ratios and then log transform the data? > > I am also looking for reviews of canonical discriminant functions analysis and stepwise discriminant function analysis in an attempt to quantitate differences between species within a genus. > > Thanks for your help. > > Brett > > ************************************ > Brett Human > Shark Researcher > 27 Southern Ave > West Beach SA 5024 > Australia > 61 8 8356 6891 > [EMAIL PROTECTED] > ************************************ > > > > == > Replies will be sent to list. > For more information see http://life.bio.sunysb.edu/morph/morphmet.html. == Replies will be sent to list. For more information see http://life.bio.sunysb.edu/morph/morphmet.html.
