R help - Oct 2006 - sorting elements of matrix by row

Dear R users,
I would like to sort elements of a matrix by row and use this ordering to 
also sort another matrix. I am trying to post-order the means of components 
for a mixture model and would also like to do the same for the component 
probabilities. This is what I have tried thus far, but I doubt whether its 
efficient given the number of replications I am using:

mean.data <- matrix(rnorm(20,0,1),10,2)
probs <- runif(10)
prob.data <- cbind(probs,1-probs)
sorted.mean <- sorted.prob <- array(0, dim=dim(mean.data))
for(i in 1:nrow(mean.data)){
    sorted.data[i,] <- mean.data[i,order(mean.data[i,])]
    sorted.prob[i,] <- prob.data[i,order(mean.data[i,])]
}

Thanks,
Vumani

Hi

maybe

swap<-function(x) x[,2:1]

can be of some help

sel<-which(mean.data[,1]>mean.data[,2])
dfm<-mean.data
dfm[sel,]<-swap(dfm[sel,])
all.equal(dfm, sorted.mean)

HTH
Petr



On 27 Oct 2006 at 10:10, Vumani Dlamini wrote:

From:           	"Vumani Dlamini" <dvumani at hotmail.com>
To:             	r-help at stat.math.ethz.ch
Date sent:      	Fri, 27 Oct 2006 10:10:27 +0000
Subject:        	[R] sorting elements of matrix by row
> Dear R users,
> I would like to sort elements of a matrix by row and use this ordering
> to also sort another matrix. I am trying to post-order the means of
> components for a mixture model and would also like to do the same for
> the component probabilities. This is what I have tried thus far, but I
> doubt whether its efficient given the number of replications I am
> using:
> 
> mean.data <- matrix(rnorm(20,0,1),10,2)
> probs <- runif(10)
> prob.data <- cbind(probs,1-probs)
> sorted.mean <- sorted.prob <- array(0, dim=dim(mean.data))
> for(i in 1:nrow(mean.data)){
>     sorted.data[i,] <- mean.data[i,order(mean.data[i,])]
>     sorted.prob[i,] <- prob.data[i,order(mean.data[i,])]
> }
> 
> Thanks,
> Vumani
> 
> ______________________________________________
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html and provide commented,
> minimal, self-contained, reproducible code.
Petr Pikal
petr.pikal at precheza.cz