[Rd] Feature Request: "matrix[1:10,1:10, block=F] <- 1:10"

Warnes, Gregory R gregory_r_warnes@groton.pfizer.com
Wed, 20 Feb 2002 16:15:12 -0500

Hi Guys,

I've again been surprised when something like

> m <- matrix("", nrow=3,ncol=3)
> index_i <- c(2,1,3)
> index_j <- c(1,3,2)
> vals    <- c("a","b","c")
> m[ index_i, index_j ] <- vals
> m

gives block-wise application of the assignment:

     [,1] [,2] [,3]
[1,] "b"  "b"  "b" 
[2,] "a"  "a"  "a" 
[3,] "c"  "c"  "c" 

when what I wanted was by-element assignment:

     [,1] [,2] [,3]
[1,]   ""   ""  "b"
[2,]  "a"   ""   ""
[3,]   ""  "c"   ""

I always end up writing the code:

> for( p in length(index_i) )
>    m[ index_i[p], index_j[p] ] <- vals[p]

to do what I want.

So, I'm thinking about creating a patch to the R source to add an optional
parameter, say "block",  to the "[<-" call for matrixes and data frames.  

When "block=T" (the default) the old behaviour is preserved.  When "block=F"
the behavior I want occures so that 

> m[ index_i, index_j, block=F ] <- vals

would do what I want.

Comments?  Cheers?  Jeers?  Silence?



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