On Nov 3, 2005, at 7:44 AM, morphmet wrote: > Good morning morphometricians > > ... > c) Again when comparing groups within a sample, is there some way of > evaluating which are the landmarks that contribure more to the observed > differences?-
Antigoni et al., I will respond to question (c), which is of most interest to me. It is clearly a multivariate analysis-of-dispersion question which can be answered by analysis of the aligned data using an analysis-of-dispersion package. This would include developing a design matrix that would include how your groups within a sample are related. You would then analyze the Y matrix of aligned data using the design matrix producing a Sums of Squares and Crossproducts from that analysis which would have SS and Crossproduct matrices due to each design feature, plus a Residual Sums of Squares and Crossproducts. Then these would be submitted to the Test-for-Additional Information. For instance, one could ask the question: Does trait 1x,y provide any additional information above and beyond trait 2-10x,y? or Do traits 1-5x,y provide any additional information above and beyond traits 6-10x,y? This powerful Analysis of Dispersion approach is described in Rao (1965). Rao, C.R., Linear Statistical Inference and Its Applications. 1965, New York NY: John Wiley. 522pp. I have implemented a package that uses this approach over the years in each subsequent language that I have been using: Fortran, Pascal, APL, J and now R. I have abandoned most of the prior language implementations and now only have sure access to the R version. I provide a set of scripts which work in the J environment that were completely functional under the J computing environment current in 2002 but I have not maintained it . This J version script is reasonably annotated with what it will do: http://www.bio.umass.edu/biology/kunkel/pub/j_scripts/ I use the R version of the Analysis of Dispersion part of it regularly but can not vouch for the Test-of-Additional-Info module yet. http://www.bio.umass.edu/biology/kunkel/pub/r_scripts/andy/ As with much personal software, it may not be friendly enough for general use by individuals unfamiliar with the math but people are welcome to play with it and modify it to their own needs. They are a simple implementation of the matrix algebra from Rao. I have never seen them implemented in another commercial package (I really have not looked) and would ask our present company of morphometricians if they have another approach or available implementation that would do the same trick? We should all not keep patting ourselves on the back for reinventing the wheel but it is a-good-thing that some of us keep checking that we can do the basic math -and- help others learn to do the relevant stuff also. This is not something that Jim's TPS suite will do and I know that he usually recommends that people take the aligned data and analyze it with available special packages. Should we urge some sort of matrix or tree of techniques be created that would allow us to direct new users to a protocol or key to be followed out from the basic alignment procedure ... what things can be done by the TPS or other suites and what needs require looking toward other packages? How about a concept map of the tools that can be used to answer morphometrics questions? Joe Kunkel [EMAIL PROTECTED] > --·. .· `·. .><((((º>`·. .· `·. .><((((º>`·. .· `·. .><((((º> > .··.· >=- =º}}}}}>< Joseph G. Kunkel, Professor Biology Department University of Massachusetts Amherst Amherst, MA 01003 http://www.bio.umass.edu/biology/kunkel/ -- Replies will be sent to the list. For more information visit http://www.morphometrics.org
