# [R] matrix manipulations

Liaw, Andy andy_liaw at merck.com
Tue Jul 15 19:21:21 CEST 2003

```I don't think for loop is so bad here, but if you insist on not using it,
try:

> x<-matrix(rnorm(25), 5, 5)
> sapply(1:5, function(i) cor(x[,i], rowSums(x[,-i])))
 -0.04179336 -0.08613796  0.48194936  0.38317629 -0.22081706

HTH,
Andy

> -----Original Message-----
> From: David Andel [mailto:andel at ifi.unizh.ch]
> Sent: Tuesday, July 15, 2003 12:52 PM
> To: r-help at stat.math.ethz.ch
> Subject: [R] matrix manipulations
>
>
> Hi
>
> cor(x,apply(x,1,sum)) gives me the correlations of each
> column with the sums of each row (correct me if I'm wrong, please).
>
> What I need are the correlations of each column with the sums
> of each row except the entry in the given column. It seems
> that for any one column i I get it by doing:
>
> cor(x[,i],apply(x[,-i],1,sum))
>
> But I struggle to get it for all the columns. I was trying
> things like:
>
> for(i in 1:ncol(x)) cor(x[,i],apply(x[,-i],1,sum))
>
> which doesn't generate any output at all, and
>
> > rbind(for(i in 1:ncol(x)) cor(x[,i],apply(x[,-i],1,sum)))
>           [,1]
> [1,] 0.1880237
>
> outputs just the result of the very last column.
>
> I know that it shouldn't be necessary to use for(), but I
> couldn't figure out a way how to do the task using e.g. apply().
>
> How do you get the results of all columns?
>
> Thank you,
> David
>
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> https://www.stat.math.ethz.ch/mailman/listinfo> /r-help
>

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