Try this:
> x <- 1:10
> pos <- c(1,4,7)
> pat <- rep(seq_along(pos), times=diff(c(pos, length(x) + 1)))
> split(x, pat)
$`1`
[1] 1 2 3
$`2`
[1] 4 5 6
$`3`
[1] 7 8 9 10
On Tue, May 4, 2010 at 11:29 AM, Joris Meys <jorism...@gmail.com> wrote:
> Dear all,
>
> I'm trying to optimize code and want to avoid for-loops as much as
> possible.
> I'm applying a calculation on subvectors from a big one, and I get the
> subvectors by using a vector of starting positions:
>
> x <- 1:10
> pos <- c(1,4,7)
> n <- length(x)
>
> I try to do something like this :
> pos2 <- c(pos, n+1)
>
> out <- c()
> for(i in 1:n){
> tmp <- x[pos2[i]:pos2[i+1]]
> out <- c(out, length(tmp))
> }
>
> Never mind the length function, I apply a far more complicated one. It's
> about the use of the indices in the for-loop. I didn't see any way of doing
> that with an apply, unless there is a very convenient way of splitting my
> vector in a list of the subvectors or so.
>
> Anybody an idea?
> Cheers
> --
> Joris Meys
> Statistical Consultant
>
> Ghent University
> Faculty of Bioscience Engineering
> Department of Applied mathematics, biometrics and process control
>
> Coupure Links 653
> B-9000 Gent
>
> tel : +32 9 264 59 87
> joris.m...@ugent.be
> -------------------------------
> Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
>
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>
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> PLEASE do read the posting guide
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>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem that you are trying to solve?
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