[R] Union of columns of two matrices

[Charles C. Berry]

On Thu, 7 Aug 2008, Dan Davison wrote:

> 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)]
> }
>
> ?


Or just

union.matrices <- function(a, b) unique( cbind( a , b ), MARGIN=2 )

Chuck


>
> (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 ::
>> Skype :: gappy3000 :: Gtalk: paleologo :: Mobile: 917.331.3497
>> fact: 2^32,582,657-1 is a prime
>>
>> 	[[alternative HTML version deleted]]
>>
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>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901