Thanks Jonathan and Ista, that's really helpful. Got it running much better
now.

Ben

On 2 March 2011 17:33, Jonathan P Daily <jdaily@usgs.gov> wrote:

> Is this what you want? I don't know what your v looks like, but this won't
> work if there are cases in which v won't sum to exactly x.
>
> x <- 20
> v <- sample(0:1, 100, T)
>
> w <- v[1:which(cumsum(v)==x)]
> --------------------------------------
> Jonathan P. Daily
> Technician - USGS Leetown Science Center
> 11649 Leetown Road
> Kearneysville WV, 25430
> (304) 724-4480
> "Is the room still a room when its empty? Does the room,
>  the thing itself have purpose? Or do we, what's the word... imbue it."
>     - Jubal Early, Firefly
>
> r-help-bounces@r-project.org wrote on 03/02/2011 10:42:12 AM:
>
> > [image removed]
> >
> > [R] Vector manipulations
> >
> > Benjamin Hartley
> >
> > to:
> >
> > r-help
> >
> > 03/02/2011 11:08 AM
> >
> > Sent by:
> >
> > r-help-bounces@r-project.org
> >
> > I have a question regarding the most efficient way to select a substring
> of
> > a vector:
> >
> > I have a vector of value v, and I want to select a subspace of this
> vector
> > called w such that:
> >
> > w=v[1:n]
> >
> > where
> >
> > sum(w) = x
> >
> > I am interested in what you thing would be the most efficient way to do
> this
> > - I would like to avoid slowing down my simulations as much as possible.
> >
> > Thank you very much for any help that anyone is able to give.
> >
> >    [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
>

	[[alternative HTML version deleted]]

