[Rd] Bug in "[<-.matrix"? (Was: Feature Request: "matrix[1:10,1:10,
block=F] <- 1:10")
Warnes, Gregory R
gregory_r_warnes@groton.pfizer.com
Wed, 20 Feb 2002 17:44:24 -0500
Thanks to David Meyer [david.meyer@ci.tuwien.ac.at] and David Brahm
[brahm@alum.mit.edu] who suggested:
m[ cbind(index.i, index.j) ] <- vals
This works fine for the example I gave.
Unfortunately, this approach doesn't extend to using the row and column
names to make assignments:
> m <- matrix("",ncol=3,nrow=3)
> dimnames(m) <- list(c("a","b","c"), c("A","B","C"))
> m
A B C
a "" "" ""
b "" "" ""
c "" "" ""
>
> index.i <- c("b","a","c")
> index.j <- c("B","A","C")
> vals <- c("1","2","3")
>
> m[ cbind(index.i, index.j) ] <- vals
> m
b a c B A C
"" "" "" "" "" "" "" "" "" "1" "2" "3" "1" "2" "3"
This looks like a bug...
-Greg
> -----Original Message-----
> From: David Brahm [mailto:brahm@alum.mit.edu]
> Sent: Wednesday, February 20, 2002 5:21 PM
> To: gregory_r_warnes@groton.pfizer.com
> Cc: r-devel@hypatia.math.ethz.ch
> Subject: [Rd] Feature Request: "matrix[1:10,1:10, block=F] <- 1:10"
>
>
> Gregory R Warnes <gregory_r_warnes@groton.pfizer.com> wrote:
> R> m <- matrix("", nrow=3,ncol=3)
> R> index_i <- c(2,1,3)
> R> index_j <- c(1,3,2)
> R> vals <- c("a","b","c")
> R> m[ index_i, index_j ] <- vals
>
> but what he wants to get is:
> > [,1] [,2] [,3]
> > [1,] "" "" "b"
> > [2,] "a" "" ""
> > [3,] "" "c" ""
>
> Just do this instead:
> R> m[ cbind(index_i, index_j) ] <- vals
>
> --
> -- David Brahm (brahm@alum.mit.edu)
>
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