[R] Idiom for column operations?

[Sundar Dorai-Raj]

Rob Steele wrote:

> Is there a better way to express operations between matrices and column 
> vectors than transposing the matrix twice?
> 
> This is the kind of thing I'm talking about:
> 
> m = matrix(1:20, 3, 4)
> v = colSums(m)
> 
> t(t(m) / v)   ## <--  kinda ugly, ain't it?
> 
> I thought of converting the column vector to a matrix:
> 
> m / matrix(v, nrow = nrow(m), ncol = length(v), byrow = TRUE)
> 
> But that seems even worse.
> 
> Thanks!
> Rob Steele
> 

Rob,

Would ?sweep be sufficient for you?

m <- matrix(1:20, 5, 4)
sweep(m, 2, colSums(m), "/")

--sundar