So what is the special behavior of the ^ symbol when not at the beginning of the string that occurs when it is not escaped? --------------------------------------------------------------------------- Jeff Newmiller The ..... ..... Go Live... DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live Go... Live: OO#.. Dead: OO#.. Playing Research Engineer (Solar/Batteries O.O#. #.O#. with /Software/Embedded Controllers) .OO#. .OO#. rocks...1k --------------------------------------------------------------------------- Sent from my phone. Please excuse my brevity.
Duncan Murdoch <murdoch.dun...@gmail.com> wrote: >On 13-01-21 11:48 AM, Jeff Newmiller wrote: >> I am not sure I understand what worked perfectly, since it is my >understanding that ^ is only special at the beginning of the regex (to >anchor the pattern at the beginning of the target string) or as the >first character of a character set (to indicate exclusion of the listed >characters). In any other position the caret should behave like an >ordinary character. That is, your original pattern should have worked >as-is. This is supported by the help page documentation for regex in >the paragraph below the definition of [:xdigit:]. I think this is a bug >in R. > >It's a documentation error rather than a bug. The ^ character is >special anywhere in the extended RE syntax defined by the TRE library >or the Perl-compatible library that we use. This is inconsistent with >the POSIX standard, which might be what you were thinking of. > >Duncan Murdoch > > > >> >--------------------------------------------------------------------------- >> Jeff Newmiller The ..... ..... Go >Live... >> DCN:<jdnew...@dcn.davis.ca.us> Basics: ##.#. ##.#. Live >Go... >> Live: OO#.. Dead: OO#.. >Playing >> Research Engineer (Solar/Batteries O.O#. #.O#. with >> /Software/Embedded Controllers) .OO#. .OO#. >rocks...1k >> >--------------------------------------------------------------------------- >> Sent from my phone. Please excuse my brevity. >> >> mtb...@gmail.com wrote: >> >>> Hi Tsjerk, many thanks...that worked perfectly! >>> >>> Mark Na >>> >>> >>> >>> On Mon, Jan 21, 2013 at 9:36 AM, Tsjerk Wassenaar ><tsje...@gmail.com> >>> wrote: >>> >>>> Oh, I'm jetlagged. ^ is a control character for 'start of string'. >In >>> the >>>> context of a character set it means negation: [^a-z]. >>>> >>>> Ciao, >>>> >>>> Tsjerk >>>> >>>> >>>> On Mon, Jan 21, 2013 at 4:33 PM, Tsjerk Wassenaar >>> <tsje...@gmail.com>wrote: >>>> >>>>> Hi Mark Na, >>>>> >>>>> Try: >>>>> >>>>> grepl("latitude\\^2",temp) >>>>> >>>>> ^ is a control character for negation, so you have to escape it. >>>>> >>>>> Cheers, >>>>> >>>>> Tsjerk >>>>> >>>>> >>>>> On Mon, Jan 21, 2013 at 4:26 PM, <mtb...@gmail.com> wrote: >>>>> >>>>>> Hello R-helpers, >>>>>> >>>>>> I am trying to search for string that includes the caret symbol, >>> using >>>>>> the >>>>>> following code: >>>>>> >>>>>> grepl("latitude^2",temp) >>>>>> >>>>>> >>>>>> And R doesn't like that. It gives me: >>>>>> >>>>>>> temp<-c("latitude^2","latitude and >>> latitude^2","longitude^2","longitude >>>>>> and longitude^2") >>>>>>> temp >>>>>> [1] "latitude^2" "latitude and latitude^2" >>> "longitude^2" >>>>>> "longitude and longitude^2" >>>>>>> grepl("latitude^2",temp) >>>>>> [1] FALSE FALSE FALSE FALSE >>>>>> >>>>>> >>>>>> I think this must a regex problem, but I can't find out to >specify >>> the >>>>>> caret using regex. >>>>>> >>>>>> I would appreciate any help you could provide. >>>>>> >>>>>> Many thanks, >>>>>> >>>>>> Mark Na >>>>>> >>>>>> [[alternative HTML version deleted]] >>>>>> >>>>>> ______________________________________________ >>>>>> R-help@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. >>>>>> >>>>> >>>>> >>>>> >>>>> -- >>>>> Tsjerk A. Wassenaar, Ph.D. >>>>> >>>>> post-doctoral researcher >>>>> Biocomputing Group >>>>> Department of Biological Sciences >>>>> 2500 University Drive NW >>>>> Calgary, AB T2N 1N4 >>>>> Canada >>>>> >>>> >>>> >>>> >>>> -- >>>> Tsjerk A. Wassenaar, Ph.D. >>>> >>>> post-doctoral researcher >>>> Biocomputing Group >>>> Department of Biological Sciences >>>> 2500 University Drive NW >>>> Calgary, AB T2N 1N4 >>>> Canada >>>> >>> >>> [[alternative HTML version deleted]] >>> >>> ______________________________________________ >>> R-help@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@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@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.