[R] Regex: workaround for variable length negative lookbehind

[Gabor Grothendieck]

On Mon, Dec 1, 2008 at 12:20 AM, Wacek Kusnierczyk
<Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
> Gabor Grothendieck wrote:
>> Try this:
>>
>>
>>> vec <- c("aaaa", "baaa", "bbaa", "bbba", "baamm", "aa")
>>>
>>
>>
>>> grep("^(?!(.)\\1{1,}$).*(.)\\2{1,}$", vec, perl = TRUE)
>>>
>
> or even
>
> grep("^(?!(.)\\1+$).*(.)\\2+$", vec, perl = TRUE)
>

Or combining the previous simplification I posted with yours:

> grep("^(?!(.)\\1+$).*(.)\\2$", vec, perl = TRUE)
[1] 2 3 5