pairs

m <- matrix(c(2,1,3,9,5,7,7,8,1,8,6,5,6,2,2,7),4,4)
p <- c(2, 6)

apply(m == p[1], 1, any) & apply(m == p[2], 1, any)

sum(apply(m == p[1], 1, any) & apply(m == p[2], 1, any))

Hi, All,

I have an n by m matrix with each entry between 1 and 15000. I want to know
the frequency of each pair in 1:15000 that occur together in rows. So for
example, if the matrix is
2 5 1 6
1 7 8 2
3 7 6 2
9 8 5 7
Pair (2,6) (un-ordered) occurs together in rows 1 and 3. I want to return
the value 2 for this pair as well as that for all pairs. Is there a fast way
to do this avoiding loops? Loops take too long.

Thank you,

Cindy

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