> -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of David.Epstein > Sent: Friday, April 09, 2010 1:36 PM > To: r-help@r-project.org > Subject: [R] perhaps regular expression bug with | sign ?? > > > Here is my interaction with R: > > sub(x='>|t|',pattern = '|t',replacement='zz') > [1] "zz>|t|" > > So I say to myself "Clearly the | signs need to be escaped, > so let's try > this" > > sub(x='>|t|',pattern = '\|t',replacement='zz') > [1] "zz>|t|" > Warning messages: > 1: '\|' is an unrecognized escape in a character string > 2: unrecognized escape removed from "\|t" > How can \| be an unrecognized escape? This flatly contradicts > help('regex'),
It would be a bit clearer if the warnings indicated that they were from the R parser (the function that converts your text input to R expressions which are later evaluated). The parser is trying to say that it is treating "\|" as "|". The backlash has special meaning in things like "\n" (newline), "\t" (tab), and "\123" (character number in octal), but not before a vertical bar. Because the parser removed the backslash sub() never saw it. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > or am I misunderstanding the help? > > The first pattern above works if one uses extended=F. > > What do R experts think? > > David > -- > View this message in context: > http://n4.nabble.com/perhaps-regular-expression-bug-with-sign- > tp1819872p1819872.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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.
