[R] splitting a vector

[William Dunlap]

The following 'f' counts the number of times the sequence x
does not increase.  Is this what you want?

> f <- function(x) split(x, cumsum(c(TRUE, x[-1] <= x[-length(x)])))
> f(numbers)
$`1`
[1] 1 2

$`2`
[1] 1 2 3 4 5

> f(c(1,1,2,3,4,5,1,2,3,2,3,4,5,6,4,5))
$`1`
[1] 1

$`2`
[1] 1 2 3 4 5

$`3`
[1] 1 2 3

$`4`
[1] 2 3 4 5 6

$`5`
[1] 4 5


Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of capy_bara
> Sent: Wednesday, August 01, 2012 6:30 AM
> To: r-help at r-project.org
> Subject: [R] splitting a vector
> 
> Hello,
> 
> I have a vector with positive integer numbers, e.g.
> 
> > numbers <- c(1,2,1,2,3,4,5)
> 
> and want to split the vector whenever an element in the vector is smaller or
> equal to its predecessor.
> Hence I want to obtain two vectors: c(1,2) and c(1,2,3,4,5).
> I tried with which(), but it is not so elegant:
> 
> > numbers[1:(which(numbers<=numbers[1])[2]-1)]
> > numbers[which(numbers<=numbers[1])[2]:length(numbers)]
> 
> Sure I can do it with a for-loop, but that seems a bit tedious for that
> small problem.
> Does maybe anyone know a simple and elegant solution for this? I'm searching
> for a general solution, since
> my vector may change and maybe be split into more than two vectors, e.g.
> give five vectors for c(1,1,2,3,4,5,1,2,3,2,3,4,5,6,4,5).
> 
> Many thanks in advance,
> 
> Hannes
> 
> 
> 
> 
> 
> 
> 
> --
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