[R] Search for locations of subsequences?

[Duncan Murdoch]

On 12-08-28 5:32 PM, Marc Schwartz wrote:
> On Aug 28, 2012, at 4:05 PM, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>
>> Is there a function to efficiently search for a subsequence within a vector?
>>
>> For example, with
>>
>> x <- 1:100
>>
>> I'd like to search for the sequence c(49,50,51), and be told that it occurs exactly once, starting at location 49.  (The items in the vectors might be numeric or character, and there might be repetitions within the search pattern or within the vector I'm searching.)
>>
>> Duncan Murdoch
>
>
> There is a thread here:
>
>    http://tolstoy.newcastle.edu.au/R/e17/help/12/02/4201.html
>
> that has various solutions and towards the end has a post with some timings.

Thanks, that's helpful.  I wonder if we should have a function based on 
the fast solution in that thread (or something even faster written all 
in compiled code; I suspect Boyer-Moore could do well, but not coded in R).

Duncan Murdoch