[Rd] Fastest non-overlapping binning mean function out there?

[Henrik Bengtsson]

Hi,

I'm looking for a super-duper fast mean/sum binning implementation
available in R, and before implementing z = binnedMeans(x y) in native
code myself, does any one know of an existing function/package for
this?  I'm sure it already exists.  So, given data (x,y) and B bins
bx[1] < bx[2] < ... < bx[B] < bx[B+1], I'd like to calculate the
binned means (or sums) 'z' such that z[1] = mean(x[bx[1] <= x & x <
bx[2]]), z[2] = mean(x[bx[2] <= x & x < bx[3]]), .... z[B].  Let's
assume there are no missing values and 'x' and 'bx' is already
ordered.  The length of 'x' is in the order of 10,000-millions.  The
number of elements in each bin vary.

Thanks,

Henrik