matrix %in% matrix

Question

Suppose I have two matrices, each with two columns and differing numbers of row. I want to check and see which pairs of one matrix are in the other matrix. If these were one

Answer 1

Another approach would be:

> paste(a[,1], a[,2], sep="$$") %in% paste(x[,1], x[,2], sep="$$")
[1] FALSE  TRUE  TRUE FALSE

A more general version of this is:

> apply(a, 1, paste, collapse="$$") %in% apply(x, 1, paste, collapse="$$")
[1] FALSE  TRUE  TRUE FALSE