On Fri, Jan 9, 2009 at 4:28 PM, Wacek Kusnierczyk <waclaw.marcin.kusnierc...@idi.ntnu.no> wrote: > Rau, Roland wrote: >> >> P.S. Any suggestions how to become more proficient with regular >> expressions? The O'Reilly book ("Mastering...")? Whenever I tried >> anything more complicated than basic usage (things like ^ $ * . ) in R, >> I was way faster to write a new function (like above) instead of finding >> a regex solution. >> > > the book you mention is good. > you may also consider http://www.regular-expressions.info/ > > regexes are usually well explained with lots of examples in perl books. > >> By the way: it might be still possible to *write* regular expressions, >> but what about code re-use? Are there people who can easily *read* >> complicated regular expressions? >> > > > in some cases it is possible to write regular expressions in a way that > facilitates reading them by a human. in perl, for example, you can use > so-called readable regexes: > > / > (.+) # match and remember at least one arbitrary character > [.] # match a dot > [^.]+ # match at least one non-dot character > $ # end of string anchor > /x; > > you can also use within regex comments: > > /(.+)(?# one or more chars)[.](?# a dot)[^.]+(?# one or more > non-dots)$(?# end of string)/ > > > nothing of the sorts in r, however.
Supports that if you begin the regular expression with (?x) and use perl = TRUE. See ?regexp ______________________________________________ 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.