[R] comparing two matrices

[Adrian Dusa]

On Sunday 21 January 2007 12:04, Dimitris Rizopoulos wrote:
> I think the following should work in your case:
>
> mat1 <- data.matrix(expand.grid(0:2, 0:2, 0:2))
> mat2 <- mat1[c(19, 16, 13, 24, 8), ]
> ############
> ind1 <- apply(mat1, 1, paste, collapse = "/")
> ind2 <- apply(mat2, 1, paste, collapse = "/")
> match(ind2, ind1)


Oh yes, I thought about that too.
It works fast enough for small matrices, but I deal with very large ones. 
Using paste() on such matrices decreases the speed dramatically.

Thanks again,
Adrian

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Adrian Dusa
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