From gregory_r_warnes@groton.pfizer.com  Wed Feb 20 22:44:24 2002
From: gregory_r_warnes@groton.pfizer.com (Warnes, Gregory R)
Date: Wed, 20 Feb 2002 17:44:24 -0500
Subject: [Rd] Bug in "[<-.matrix"?   (Was: Feature Request: "matrix[1:10,1:10,
 block=F] <- 1:10")
Message-ID: <5429125E11E4D411AF7300805FE603A8040DE6CF@groexmbcr02.pfizer.com>



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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[Rd] Bug in "[<-.matrix"? (Was: Feature Request: "matrix[1:10,1:10, block=F] <- 1:10")
Warnes, Gregory R