[R] Question to regular expressions

[Prof Brian Ripley]

Antje wrote:
> Hi Gabor,
> 
> it works! Thank you very much! But I still don't understand the 
> difference between [0-9] and [:digit:]...

If all else fails, read the help, here ?regex.  Both [0-9] and 
[[:digit:]] are character classes of digits, but the first contains only 
arabic numerals.  In some locales the second may contain other numerals 
(e.g. Japanese has other characters representing digits): however I 
believe that in the current R implementations that no other numerals are 
included in any locale.



> Ciao,
> Antje
> 
> 
> Gabor Grothendieck schrieb:
>> Try this:
>>
>>> folders <- c("folder1", "f2", "F234562", "12345678", "234567", 
>>> "912345", "333")
>>> grep("^[0-9]{6}$", folders, value = TRUE)
>> [1] "234567" "912345"
>>
>>
>> On Tue, Dec 2, 2008 at 10:32 AM, Antje <niederlein-rstat at yahoo.de> wrote:
>>> Hi there,
>>>
>>> I know, this question is not directly an R-help question but probably
>>> someone can give me a hint how to deal with the following problem.
>>>
>>> I have a vector with file/folder names and want to filter for all 
>>> entries
>>> which  have 6 numbers in a row and nothing else.
>>>
>>> folders <- c("folder1", "f2", "F234562", "12345678", "234567", "912345",
>>> "333")
>>>
>>> I'd like to get only "234567" and "912345".
>>> Can anybody help me creating a regex for this???
>>>
>>> For example this regex:
>>>
>>> regexpr("[^:digit:$]{6}", folders)
>>>
>>> would match "F234562", "12345678", "234567", "912345"
>>>
>>>
>>> Antje
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide 
>>> http://www.R-project.org/posting-guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>>>
>>
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.


-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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