[R] Setting matrix dimnames in a list

[Marc Schwartz]

on 05/08/2008 12:33 PM statmobile wrote:
> Hey All,
> 
> I was wondering if I could solicit a little input on what I'm trying
> to do here.  I have a list of matrices, and I want to set their
> dimnames, but all I can come up with is this:
> 
> x <- matrix(1:4,2) y <- matrix(5:8,2)
> 
> z <- list(x,y) nm <- c("a","b") nms <- list(nm,nm)
> 
> z <- lapply(z,function(x)dimnames(x)<-nms)
> 
> As you can see, this doesn't quite work.  Could anybody help me, and
>  bonus points if you can help me do this efficiently.  Please cc my
> email address, because I only get summaries of the list.
> 
> Thanks in advance!

The problem is that dimnames() does not return the matrix, so you need 
to explicitly return 'x':

 > lapply(z, function(x) {dimnames(x) <- nms; x})
[[1]]
   a b
a 1 3
b 2 4

[[2]]
   a b
a 5 7
b 6 8


HTH,

Marc Schwartz