[R] Computting statistics on a matrix with 2 factor column
Chuck Cleland
ccleland at optonline.net
Tue Jun 8 15:44:02 CEST 2004
?tapply
?aggregate
You probably have a data frame, not a matrix.
Marc Mamin wrote:
> I suppose this is a basic question but couldn't find a solution.:
>
> I have a large matrix with let say 3 columns:
>
> V1 V2 V3
> a x 2
> a x 4
> a y 8
> b z 16
>
> and I want to compute some statistics based on
> the levels resulting form the combination of the two first columns
>
> e.g.:
>
> SUM->
>
> V1 V2 V3
> a x 6
> a y 8
> b z 16
--
Chuck Cleland, Ph.D.
NDRI, Inc.
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