[R] find a sequence of characters in a vector

[Greg Snow]

Here is one approach (this could be wrapped into a function if you are applying it repeatedly):

> one <- c("a","z","e")
> two <- c("a","z","e","r","t","a","z","a","z","e","c")
> 
> which( sapply( 1:(length(two)-length(one)+1), 
+ function(i) isTRUE( all.equal( one, two[ i + 0:(length(one)-1) ] ) ) ) )
[1] 1 8
>

Hope this helps,

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Ptit_Bleu
> Sent: Friday, June 05, 2009 7:22 AM
> To: r-help at r-project.org
> Subject: [R] find a sequence of characters in a vector
> 
> 
> 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
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> 
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