[R] Discriminant Function Analysis
ligges at statistik.uni-dortmund.de
Thu Jul 7 11:05:48 CEST 2005
michael watson (IAH-C) wrote:
> 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?
No, obviously not "an ideal method", if used as is on the whole data.
Alternatives are certainly described in the literature - I am not
specialised in this field (I mean, this gene stuff), hence do not want
to specify misleading references here.
>>1) First problem, I got this error message:
>>>z <- lda(C0GRP_NA ~ ., dpi30)
>>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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