[R] Discriminant Function Analysis

michael watson (IAH-C) michael.watson at bbsrc.ac.uk
Thu Jul 7 10:58:04 CEST 2005

Thanks for the answers Uwe!

So this is a common problem in biology - few number of cases and many,
many variables (genes, proteins, metabolites, etc etc)! 

Under these conditions, is discriminant function analysis not an ideal
method to use then?  Are there alternatives?

> 1) First problem, I got this error message:
>>z <- lda(C0GRP_NA ~ ., dpi30)
> Warning message:
> variables are collinear in: lda.default(x, grouping, ...) 
> I guess this is not a good thing, however, I *did* get a result and it

> discriminated perfectly between my groups.  Can anyone explain what 
> this means?  Does it invalidate my results?

Well, 14 cases and 37 variables mean that not that many degrees of 
freedom are left.... ;-)
Of course, you get a perfect fit - with arbitrary data.

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