[R] intersecting rows of a matrix

[Gabor Grothendieck]

Try this:

do.call(intersection, unname(as.data.frame(t(mat))))


On Wed, Feb 20, 2008 at 6:45 PM, dxc13 <dxc13 at health.state.ny.us> wrote:
>
> 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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