[R] Hep with regex! - combination of ^, |, \\, _ and $

[Dimitri Liakhovitski]

Thank you very much, guys!
As always - great learnings for me! Esp. + vs. *

On Fri, Sep 18, 2015 at 8:48 AM, Upton, Stephen (Steve) (CIV)
<scupton at nps.edu> wrote:
> And unless I'm mistaken, escaping the underscore is superfluous (I'd be curious to know if it's a function of locale).
>
> x[grep("_", x)]
>
> x[grep("^q10.*_1$", x)]
>
> both work.
>
> steve
>
> Stephen C. Upton
> SEED (Simulation Experiments & Efficient Designs) Center
> Operations Research Department
> Naval Postgraduate School
> SEED Center web site: http://harvest.nps.edu
>
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Berend Hasselman
> Sent: Friday, September 18, 2015 1:30 AM
> To: Dimitri Liakhovitski
> Cc: r-help
> Subject: Re: [R] Hep with regex! - combination of ^, |, \\, _ and $
>
>
>> On 17 Sep 2015, at 23:11, Dimitri Liakhovitski <dimitri.liakhovitski at gmail.com> wrote:
>>
>> (x <- c("q10_1", "q10_2", "q10_11", "q12_1", "q12_2", "q13_1",
>> "q13_11"))
>>
>> # Which strings start with "q10" or "q12? - WORKS x[grep("^q10|q12",
>> x)]
>>
>> # Which strings end with "1"? - WORKS
>> x[grep("1$", x)]
>>
>> # Which strings end with "_1"? - WORKS x[grep("\\_1$", x)]
>>
>> # Which strings start with "q10" AND contain a "1"? - WORKS
>> x[grep("^q10.+1", x)]
>>
>
> For these last to this should “work”
>
>> # Which strings start with "q10" AND end with a "_1"? - DOES NOT WORK
>> x[grep("^q10.+\\_1$", x)]
>>
>
> x[grep("^q10.*\\_1$", x)]
>
>> # Which strings start with "q10" or "q12 AND end with "_1"? - WORKS
>> INCORRECTLY x[grep("^q10|q12.+\\_1$", x)]
>>
>
> x[grep("^q10|q12.*\\_1$", x)]
>
> It’s the .+ that’s the problem.
>
> Berend
>
>> Thank you!
>> Dimitri Liakhovitski
>>
>> ______________________________________________
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>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.



-- 
Dimitri Liakhovitski