Hi,
You don't say what you want to do with the output, or whether you want
to do it with more than one value, but here's one of the many possible
ways to get your example:
R> A <- matrix(c(1,1,2,2,2,2,1,1), nrow=2, byrow=TRUE)
R> B <- matrix(c(3,4,2,1,1,1,2,2), nrow=2, byrow=TRUE)
R> A
[,1] [,2] [,3] [,4]
[1,] 1 1 2 2
[2,] 2 2 1 1
R> B
[,1] [,2] [,3] [,4]
[1,] 3 4 2 1
[2,] 1 1 2 2
R> ifelse(A == 1, B, 0)
[,1] [,2] [,3] [,4]
[1,] 3 4 0 0
[2,] 0 0 2 2
R> rowSums(ifelse(A == 1, B, 0))
[1] 7 4
Sarah
On Thu, Sep 26, 2013 at 5:51 PM, tobias schlager <tobebry...@me.com> wrote:
> Dear all,
>
> I have a big problem:
> - I got two matrices, A and B
> - A shows identifies the value of B, however the values of B must be summed
> - For instance,
> 1 1 2 2
> 2 2 1 1
> gives matrix a
> 3 4 2 1
> 1 1 2 2
> gives matrix b
>
> Now the result for the value 1 would be
> 7
> 4
> which are the rowsums of the values of matrix B given that matrix A has the
> value 1.
>
>
> How can I do this automatically? I am really puzzled here. Thanks for your
> help guys,
> Tobi
--
Sarah Goslee
http://www.functionaldiversity.org
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
