r - Find closest value in a vector with binary search

Question

As a silly toy example, suppose

x=4.5
w=c(1,2,4,6,7)

I wonder if there is a simple R function that finds the index of the closest match to x in w. So if foo is that function, foo(w,x) would return 3. The function match is the right idea, but seems to apply only for exact matches.

Solutions here (e.g. which.min(abs(w - x)), which(abs(w-x)==min(abs(w-x))), etc.) are all O(n) instead of log(n) (I'm assuming that w is already sorted).

Answer 1

R>findInterval(4.5, c(1,2,4,5,6))
[1] 3

will do that with price-is-right matching (closest without going over).