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?
-Greg
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