R help - Jan 2008 - permutates and/or samples a matrix

Hi,

sample(x) only permutates and/or samples from a vector, which I can't use
for a matrix. Please help.

Thanks
Stanley

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What exactly is the question? Selecting/permuting rows?

M[sample(length=nrow(M), count), ]

Selecting/permuting columns?

M[ , sample(length=ncol(M), count) ]

Permuting elements?

structure(sample(M), dim=dim(M))

Selecting elements?

sample(M, count)

Gabor

On Thu, Jan 31, 2008 at 09:10:11PM +0800, Ng Stanley
wrote:
> Hi,
> 
> sample(x) only permutates and/or samples from a vector, which I can't
use
> for a matrix. Please help.
> 
> Thanks
> Stanley
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Csardi Gabor <csardi at rmki.kfki.hu>    UNIL DGM

On 31 Jan 2008, you wrote in gmane.comp.lang.r.general:
> Hi,
> 
> sample(x) only permutates and/or samples from a vector, which I
> can't use for a matrix. Please help.
 
You just feed sample(.) a "redimensioned" object. If you need to do it
programmatically just multiply the dimensions of the matrix to create a 
length for the working vector.
> xm<-rnorm(25)
> xmtx<-matrix(xm,dim<-c(5,5))
> samp<-sample(as.matrix(xmtx,dim<-c(1,25)))
> samp
#output of 25 numbers elided
> samp<-sample(as.matrix(xmtx,dim<-c(1,25)),10)
> samp
 [1]  0.26421745  0.63888288  1.06176705 -1.56074510 -0.72471549 -
0.38743020
 [7] -0.68765683  1.18081648 -1.51566762  0.07560708

-- 
David Winsemius