[R] regular exprs

[David Winsemius]

On Nov 7, 2010, at 10:15 AM, Dimitris Rizopoulos 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.

 > x[ grepl("Ass", x) & !grepl("Ass\\.s", x) ]
[1] "Ass1" "Ass2"

HTH;
-- 
David

>
> 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

David Winsemius, MD
West Hartford, CT