[R] Chopping a vector up into smaller vectors

[Eik Vettorazzi]

Hi Stephen,
how about this:

chop<-function(x,counts){
 stopifnot(sum(counts)==length(x))
 split(9:1,unlist(mapply(rep,seq_along(counts),counts)))
}
chop(9:1,c(3,2,4))

cheers

Am 02.08.2012 12:29, schrieb Stephen Eglen:
> Anyone got a neat way to chop a vector up into smaller subvectors?
> This is what I have now, which seems inelegant:
> 
> chop <- function(v, counts) {
>   stopifnot(sum(counts)==length(v))
>   end <- cumsum(counts)
>   beg <- c(1, 1+end[-length(end)])
>   begend <- cbind(beg, end)
>   apply(begend, 1, function(x) v[x[1]:x[2]])
> }
>   
> 
>> chop(9:1, c(3,2,4))
> [[1]]
> [1] 9 8 7
> 
> [[2]]
> [1] 6 5
> 
> [[3]]
> [1] 4 3 2 1
> 
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Eik Vettorazzi

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