Re: [R] Variable Selection for data reduction and discriminant anlaysis

Hi Gareth, >> My data is transformed to the clr or alr under Aitchison geometry, so I >> am essentially working >> in Euclidean space. Great: glad to hear it. >> Has anyone had experience doing stepwise LDA?? I can't for the life of >> me find any help >> online about where to start. A bett

Re: [R] Variable Selection for data reduction and discriminant anlaysis

Thanks Mark, I failed to mention that i'm working within a compositional framework. I didn't want to confuse things. My data is transformed to the clr or alr under Aitchison geometry, so I am essentially working in Euclidean space. Has anyone had experience doing stepwise LDA?? I can't for t

Re: [R] Variable Selection for data reduction and discriminant anlaysis

There are some pointers to packages for variable selection in the task view for Chemometrics and Computational Physics at http://cran.r-project.org/web/views/ChemPhys.html On Sun, 21 Sep 2008, Gareth Campbell wrote: > Hello all, > > I'm dealing with geochemical analyses of some rocks. > > If I us

Re: [R] Variable Selection for data reduction and discriminant anlaysis

Hi Gareth, >> If I use the full composition (31 elements or variables), I can get >> reasonable separation of my 6 sources. A word of advice: You need to be exceptionally careful when analyzing compositional data. Taking compositions puts your data values into a constrained/bounded space (genera

[R] Variable Selection for data reduction and discriminant anlaysis

Hello all, I'm dealing with geochemical analyses of some rocks. If I use the full composition (31 elements or variables), I can get reasonable separation of my 6 sources. Then when I go onto do LDA with the 6 groups, I get excellent separation. I feel like I should be reducing the variables to