Dear Maciej,

are you perhaps looking for the aggregate function, such as in example
below?

#Generate matrix with duplicated row names
mat<-matrix(rnorm(60), nrow=12)
row.names(mat)<-rep(letters[1:c(nrow(mat)/3)], each=3)

# Merge rows in matrix using median
aggregate(mat, by=list(row.names(mat)), FUN=median)

Hope it helps!
Ales

2011/9/25 mjonczyk <mjonczyk@biol.uw.edu.pl>

> Dear List Members,
>
> I have problem with ExpressionSet object. I've constructed such an object
> with data with
> duplicated gene Ids (after assigment of probes IDs to genes).
> I know that ExpressionSet doesn't support such a situation, but I've
> thought that function
> poe.mcmc from metaArray package will handle it without problems -
> unfortunately,
> after few hours of computing I've had an error.
>
> So I'd like to ask how can I compute an average or -better- median for
> duplicated IDs in
> exprs() slot in ExpressionSet object. Or just for matrix, so I could set it
> as an exprs().
> I suspect it's basic function in R, but I've spent all day searching it and
> I haven't succeeded.
> I'd also prefer not to convert ExpressionSet to another data type (e.g.
> MAList, RGList)
> in order to perform such an operation.
>
> Any help will be valuable,
> Best Regards
>
> --
> Maciej Jonczyk,
> Department of Plant Molecular Ecophysiology
> Institute of Plant Experimental Biology
> Faculty of Biology, University of Warsaw
> 02-096 Warszawa, Miecznikowa 1
>
>
>
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-- 
Aleš Maver
Ales.Maver@gmail.com

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