I have two columns and I want to count hwo many pairs I have of the same
element. For example. If I have
a = c(1,2,3,4,5)
b= c(12, 1, 34, 2, 5, 0, 10, 100, 11)
It should return 3 (since 1, 2 and 5 occur in both columns).
Columns need not be of the same length.

-- 
Thanks,
Jim.

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