[R] find a sequence of characters in a vector

[Gabor Grothendieck]

I think I would use Sundar's solution but here are a couple
more just in case:

> x <- c("a", "z", "e")
> y <- c("a", "z", "e", "r", "t", "a", "z", "a", "z", "e", "c")
>
> #1
> which(apply(embed(y, 3), 1, identical, rev(x)))
[1] 1 8

> #2
> library(zoo)
> which(rollapply(zoo(y), 3, identical, x, align = "left"))
[1] 1 8


On Fri, Jun 5, 2009 at 9:30 AM, Sundar Dorai-Raj<sdorairaj at gmail.com> wrote:
> use gregexpr and paste
>
>> aze <- paste(c("a", "z", "e"), collapse = "")
>> sequence <- paste(c("a","z","e","r","t","a","z","a","z","e","c"), collapse = "")
>> gregexpr(aze, sequence, fixed = TRUE)
> [[1]]
> [1] 1 8
> attr(,"match.length")
> [1] 3 3
>
> HTH,
>
> --sundar
>
> On Fri, Jun 5, 2009 at 6:22 AM, Ptit_Bleu<ptit_bleu at yahoo.fr> wrote:
>>
>> Hello,
>>
>> I'm just looking for an easy way to find the positions of a complete
>> sequence in a bigger vector.
>> For example :
>> c("a","z","e") in c("a","z","e","r","t","a","z","a","z","e","c")
>> and the result should be
>> 1 8
>> that is the positions of the beginning of the complete sequence.
>>
>> I tried with %in%, match, is.element but all I get is, for example
>> which(c("a","z","e") in c("a","z","e","r","t","a","z","a","z","e","c"))
>> 1 2 3
>> meaning that each character is in the bigger vector.
>>
>> It must be easy, except for me. Sorry.
>>
>> If you have a solution, thanks in advance to share it.
>> Have a good week-end,
>> Ptit Bleu.
>>
>> --
>> View this message in context: http://www.nabble.com/find-a-sequence-of-characters-in-a-vector-tp23888063p23888063.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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>
> ______________________________________________
> R-help at r-project.org mailing list
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>