[R] Regular expression problem

[Sebastien.Bihorel at cognigencorp.com]

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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