On Jul 16, 2009, at 6:41 PM, Ross Boylan wrote:
If m is a matrix and s is a logical matrix of the same dimensions, I'd
like to be able to update m with
m[s] <- 0
If m2 is another matrix, I'd also like to be able to do
m[s] <- m2
where elements of m for which s is TRUE get the corresponding
element of
m2.
However, this doesn't work in R 2.7.1. The best I've been able to
come
up with is
s
[,1] [,2] [,3]
[1,] TRUE FALSE FALSE
[2,] TRUE TRUE TRUE
[3,] TRUE FALSE TRUE
x
[,1] [,2] [,3]
[1,] 1 4 7
[2,] 2 5 8
[3,] 3 6 9
ifelse(s, x, 0) # x[s] <- 0
[,1] [,2] [,3]
[1,] 1 0 0
[2,] 2 5 8
[3,] 3 0 9
Is there a better way?
Upgrade? .... your hoped-for "better way" works in 2.9.1
> X <- matrix(1:9, ncol=3)
> s <- matrix(c(T,T,T,FALSE,T,FALSE,FALSE,T,T),nrow=3)
> X[s] <- 0
> X
[,1] [,2] [,3]
[1,] 0 4 7
[2,] 0 0 0
[3,] 0 6 0
You _are_ asked to upgrade before posting.
And the analogous method for "works" for substituting from a third
matrix:
> M2 <- matrix(21:29, nrow=3)
> X[s] <- M2[s]
> X
[,1] [,2] [,3]
[1,] 21 4 7
[2,] 22 25 28
[3,] 23 6 29
--
David Winsemius, MD
Heritage Laboratories
West Hartford, CT
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