[R] regular exprs

[David Winsemius]

On Nov 7, 2010, at 10:30 AM, David Winsemius wrote:

>
> 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"

Or if locations were needed the:

 > setdiff( grep("Ass", x) , grep("Ass\\.s", x) )
[1] 1 3

>
> 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
>
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David Winsemius, MD
West Hartford, CT