[R] Finding (Ordered Subvectors)

[Gustavo Carvalho]

This function might be helpful:

bleh <- function(a, b) {
  where <- list()
  matches <- 0
  first <- which(a == b[1])
  for (i in first) {
    seq.to.match <- seq(i, length = length(b))
    if (identical(a[seq.to.match], b)) {
      matches <- matches + 1
      where[[matches]] <- seq.to.match
    }
  }
  return(where)
}

a<-c(3,4,3,0,4,5,6,9,3,4)
b<-c(0,4,5)
c<-c(5,4,0)
d<-c(3,4)
bleh(a, b)
bleh(a, c)
bleh(a, d)

Cheers,

Gustavo.

On Tue, Sep 21, 2010 at 11:31 AM, Lorenzo Isella
<lorenzo.isella at gmail.com> wrote:
> Dear All,
> Consider a simple example
>
> a<-c(1,4,3,0,4,5,6,9,3,4)
> b<-c(0,4,5)
> c<-c(5,4,0)
>
> I would like to be able to tell whether a sequence is contained (the order
> of the elements does matter) in another one e.g. in the example above, b is
> a subsequence of a, whereas c is not. Since the order matters, I cannot
> treat the sequences above as sets (also, elements are repeated).
> Does anyone know a smart way of achieving that?
> Many thanks
>
> Lorenzo
>
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