[R] Regular expression problem

[jim holtman]

CHeck out this site:

http://www.quanetic.com/Regex

you can google 'regular expression tester' and find it.  R uses the
standard (whatever that is) expressions so check out tutorials you
might find via google.

On Tue, Sep 15, 2009 at 8:16 PM,  <Sebastien.Bihorel at cognigencorp.com> wrote:
> Thanks Jim and Rolf,
>
> grep("n.*mytype",mystr) will do.
>
> I thought that * only applies on group of characters defined in a []
> sequence. Would you be aware of any documentation/tutorial that would give
> slightly more detail and examples that the ?regexp?
> Also, would you be aware of any (online) tool to test "R-style" regular
> expression against some text or strings?
>
>
>>
>> On 16/09/2009, at 9:58 AM, jim holtman wrote:
>>
>>> try:
>>>
>>>> grep("n.*mytype",mystr)
>>> [1] 1
>>>
>>>
>>> with the [.] it is a class with a period.  '.*' match zero, or
>>> more, characters.
>>
>> Perhaps the OP wants
>>
>>       grep("n[.].*mytype",mystr)
>>
>> to insist that ``mystr'' contain the string ``n.'' (literal ``.'')
>> somewhere before the string ``mytype''.
>>
>>       cheers,
>>
>>               Rolf Turner
>>>
>>> On Tue, Sep 15, 2009 at 5:52 PM, Sebastien Bihorel
>>> <sebastien.bihorel at cognigencorp.com> wrote:
>>>> Dear R-users,
>>>>
>>>> I am trying to use the grep function to test whether a particular
>>>> string is
>>>> of the form "n.../mydir/myfile.mytype.myext". Anything between n
>>>> and mytype
>>>> could vary, and anything after mytype could vary. I tried to
>>>> proceed by
>>>> steps to build my regular expression... but I do not really
>>>> understand why
>>>> the last call of the following code do not work.
>>>>
>>>> Any help would be greatly appreciated.
>>>>
>>>> mystr <- "n.../mydir/myfile.mytype.myext"
>>>>
>>>> grep("mytype",mystr)
>>>> # returns 1
>>>>
>>>> grep("[.]*mytype",mystr)
>>>> # returns 1
>>>>
>>>> grep("n[.]*mytype",mystr)
>>>> # returns integer(0)
>>>>
>>>>
>>>> Sebastien
>>>>
>>>> ______________________________________________
>>>> 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.
>>>>
>>>
>>>
>>>
>>> --
>>> Jim Holtman
>>> Cincinnati, OH
>>> +1 513 646 9390
>>>
>>> What is the problem that you are trying to solve?
>>>
>>> ______________________________________________
>>> 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.
>>
>>
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>
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?