Dear Jacy,
If AT and TA always one after the other, you might consider the following as
an alternative:
res <- apply(a, 2, function(x) c(x[1], sum(x[2:3]), x[4] ))
rownames(res) <- rownames(a)[-3]
res
#[,1] [,2] [,3] [,4]
#AA 1 5 9 13
#AT 5 13 21 29
#TT 4 8 12 16
HTH,
Jorge
On Mon, May 11, 2009 at 4:53 PM, Crosby, Jacy R
<jacy.r.cro...@uth.tmc.edu>wrote:
> I'm working with genotype data in a frequency table:
>
> > a=matrix(1:16, nrow=4)
> > rownames(a)=c("AA","AT","TA","TT")
> > a
> [,1] [,2] [,3] [,4]
> AA 1 5 9 13
> AT 2 6 10 14
> TA 3 7 11 15
> TT 4 8 12 16
>
> 'AT' and 'TA' are essentially the same, and I'd like to combine (add) the
> rows to reflect this. The final matrix should be:
>
> [,1] [,2] [,3] [,4]
> AA 1 5 9 13
> AT 5 13 21 29
> TT 4 8 12 16
>
> Is there a fast way to do this?
>
> Thanks in advance!
>
> Jacy Crosby
> jacy.r.cro...@uth.tmc.edu
>
>
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>
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