[R] Union of columns of two matrices

[Dan Davison]

On Wed, Aug 06, 2008 at 06:32:43PM -0400, Giuseppe Paleologo wrote:
> I was posed the following problem/teaser:
> 
> given two matrices, come up with an "elegant" (=fast & short) function that
> returns a matrix with all and only the non-duplicated columns of both
> matrices; the column order does not matter. In essence, a matrix equivalent
> of union(x,y), where x and y are vectors. I could not come with anything
> nice. Any ideas?

union.matrices <- function(a, b) {
    u <- cbind(a,b)
    u[,!duplicated(u, MARGIN=2)]
}

?

(Obviously not attempting to deal with issues of identity of columns containing real numbers)

Dan

> 
> Giuseppe
> 
> -- 
> Giuseppe A. Paleologo :: Email: paleologo at gmail.com :: AOL: gappy3000 ::
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