# [R] Finding and manipulation clusters of numbers in a sequence of numbers

William Dunlap wdunlap at tibco.com
Mon Jul 16 21:51:59 CEST 2012

```Is f() what you want?  It wastes some time doing things that don't
have to be done but is pretty easy to understand.
> input <- c(0, 0, 0, 2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0,
+ 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 0, 2, 0, 0, 2)
> out <- c(0, 0, 0, 3, 3, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0,
+ 0, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 0, 2, 0, 2, 0, 0, 2)
> f <- function (x)  {
firstInRun <- function(x) c(TRUE, x[-1] != x[-length(x)])
group <- cumsum(firstInRun(x == 0))
ave(x, group, FUN = sum)
}
> all.equal(out, f(input))
[1] TRUE

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 mdvaan
> Sent: Monday, July 16, 2012 9:18 AM
> To: r-help at r-project.org
> Subject: [R] Finding and manipulation clusters of numbers in a sequence of numbers
>
> Hi,
>
> I have the following sequence:
> in <- c(0, 0, 0, 2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0,
> 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 0, 2, 0, 0, 2)
>
> >From this sequence I would like to get to the following sequence:
> out <- c(0, 0, 0, 3, 3, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0,
> 0, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 0, 2, 0, 2, 0, 0, 2)
>
> Basically, what I would like to do for each number greater than 0,  is to
> until one of those numbers is equal to 0.
>
> I could manually repeat the loops below until "sequence" stops changing but
> there must be a smarter way. Any suggestions? Thanks!
>
> sequence <- c(0, 0, 0, 2, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0,
> 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 2, 0, 2, 0, 0, 2)
>     for (h in 2:(length(sequence) - 1))
>       {
>       sequence[h] <- ifelse(sequence[h] > 0, sequence[h-1] + sequence[h], 0)
>       }
>
>     for (h in 1:(length(sequence) - 1))
>       {
>       sequence[h] <- ifelse(sequence[h] > 0 & sequence[h+1] > sequence[h],
> sequence[h+1], sequence[h])
>       }
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Finding-and-
> manipulation-clusters-of-numbers-in-a-sequence-of-numbers-tp4636661.html
> Sent from the R help mailing list archive at Nabble.com.
>
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