Try this:

grep("Ass[^\\.]", x)


On Sun, Nov 7, 2010 at 1:15 PM, Dimitris Rizopoulos <
d.rizopoulos@erasmusmc.nl> wrote:

> Dear All,
>
> I would appreciate any help with the following: given the vector 'x'
>
> x <- c("Ass1", "Ass.s1", "Ass2", "Ass.s2")
>
> I would like to pick up the positions where the character string contains
> "Ass" but does not contain "Ass.s", so for 'x' that would be positions 1 and
> 3.
>
> I guess this could be programmed around grep() using a suitable regular
> expression, but I haven't managed to succeed.
>
> Thanks in advance.
>
> Best,
> Dimitris
>
> --
> Dimitris Rizopoulos
> Assistant Professor
> Department of Biostatistics
> Erasmus University Medical Center
>
> Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
> Tel: +31/(0)10/7043478
> Fax: +31/(0)10/7043014
> Web: http://www.erasmusmc.nl/biostatistiek/
>
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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