Try this:

matrix(apply(u, 1, tcrossprod), nr = nrow(u)*ncol(u), byrow = T)

On Mon, Jan 19, 2009 at 3:39 PM, Stephan Lindner <lindners@umich.edu> wrote:

> Dear all,
>
>
> I have a simple question which I unfortunately do not seem to be able
> to solve myself. I have a (NxK) matrix and want to generate a new
> matrix by multiplying each row with itself such that the new matrix
> has dimension ((N*K)xK) (or better, generate an array with dimension
> (K,K,N)). I tried apply, but that did not work. Any suggestions?
>
> Thanks!
>
>
>        Stephan
>
>
>
> ## Here is a simple example:
>
> u <- matrix(c(1,2,3,4,5,6,7,8,9,10),nrow=2)
>
> ## What I want to obtain
>
> u[1,]%*%t(u[1,])
> u[2,]%*%t(u[2,])
>
> ## stacked together --> 10x5 matrix
>
>
> ## This does not work
>
> sq <- function(x)x%*%t(x)
> apply(u,1,function(y)sq(y))
>
>
>
>
>
>
> --
> -----------------------
> Stephan Lindner
> University of Michigan
>
> ______________________________________________
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> 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.
>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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