Re: [R] Discriminant Function Analysis

From: Uwe Ligges <ligges_at_statistik.uni-dortmund.de>
Date: Thu 07 Jul 2005 - 19:05:48 EST

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.

Uwe Ligges

>

>>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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