[R] sum portions of a vector

[Sam Steingold]

How do I sum portions of a vector into another vector?
E.g., for
--8<---------------cut here---------------start------------->8---
> vec <- 1:10
> breaks <- c(3,8,10)
--8<---------------cut here---------------end--------------->8---
I want to get a vector of length 3 with content
--8<---------------cut here---------------start------------->8---
6 = 1+2+3
30 = 4+5+6+7+8
19 = 9+10
--8<---------------cut here---------------end--------------->8---
Obviously, I could write a loop, but I would rather have a vectorized
version.
Thanks!

-- 
Sam Steingold (http://sds.podval.org/) on Ubuntu 12.04 (precise) X 11.0.11103000
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