I’m ‘not in’ right now…
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Checking whether an item is in a vector or not in a vector is a common task. The notation in R is a little inelegant when expressing the “not in” condition since the negation operator (!
) is separated from the comparison operator (%in%
):
5 %in% c(1, 2, 3, 4, 5) # TRUE
!5 %in% c(1, 2, 3, 4, 5) # FALSE
R is a language where you can easily extend the set of built in operators:
`%!in%` <-
function(needle, haystack) {
!(needle %in% haystack)
}
Now, I can express my intentions reasonably clearly with my new, compact, infix operator %!in%
:
5 %in% c(1, 2, 3, 4, 5) # TRUE
5 %!in% c(1, 2, 3, 4, 5) # FALSE
Moral: bend your tools to your will, not the other way ’round.
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