[R] intersecting rows of a matrix

dxc13 dxc13 at health.state.ny.us
Thu Feb 21 00:45:29 CET 2008


useR's,

First, I would like to say thanks to John Fox for providing this segment of
code to perform intersection for multiple sets:
intersection <- function(x, y, ...){
 	if (missing(...)) intersect(x, y)
	else intersect(x, intersection(y, ...))
}

I want to execute this function on the rows of a matrix I have:
Ik.mat.test <- matrix(c(2,3,6,1,2,6,6,1,2),byrow=T,nrow=3)
> Ik.mat.test
     [,1] [,2] [,3]
[1,]    2    3    6
[2,]    1    2    6
[3,]    6    1    2

I need to find a way to run the intersection function on the rows of this
matrix.  The result should be a vector containing 2, 6.  
This works, but I want to find a way to do this for any size matrix.
intersection(Ik.mat.test[1,],Ik.mat.test[2,], Ik.mat.test[3,])
So, if the user supplied a matrix with any number of rows, I would like to
be able to run this function.  Any ideas?
I have tried something like
do.call(intersection, list(Ik.mat.test[1,]: Ik.mat.test[3,]))
but this doesnt work

Thanks in advance.
Derek



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