Well, that's why it was only provided when you insisted. This is not what regexp's are good at.
On Sun, Jan 18, 2009 at 4:35 PM, Rau, Roland <r...@demogr.mpg.de> wrote: > Thanks! (I have to admit, though, that I expected something simple) > > Thanks, > Roland > > > > -----Original Message----- > From: Gabor Grothendieck [mailto:ggrothendi...@gmail.com] > Sent: Sun 1/18/2009 8:54 PM > To: Rau, Roland > Cc: r-help@r-project.org > Subject: Re: [R] regex -> negate a word > > Try this: > > grep("^([^a]|a[^b]|ab[^c])*.{0,2}$", x, perl = TRUE) > > > On Sun, Jan 18, 2009 at 2:37 PM, Rau, Roland <r...@demogr.mpg.de> wrote: >> Thank you very much to all of you for your fast and excellent help. >> Since the "-grep(...)" solution seems to be favored by most of the >> answers, >> I just wonder if there is really no regular expression which does the >> job?!? >> >> Thanks again, >> Roland >> >> >> >> -----Original Message----- >> From: Gabor Grothendieck [mailto:ggrothendi...@gmail.com] >> Sent: Sun 1/18/2009 8:28 PM >> To: Rau, Roland >> Cc: r-help@r-project.org >> Subject: Re: [R] regex -> negate a word >> >> Try this: >> >> # indexes >> setdiff(seq_along(x), grep("abc", x)) >> >> # values >> setdiff(x, grep("abc", x, value = TRUE)) >> >> Another possibility is: >> >> z <- "abc" >> x0 <- c(x, z) # to handle no match case >> x0[- grep(z, x0)] # values >> >> >> >> >> On Sun, Jan 18, 2009 at 1:35 PM, Rau, Roland <r...@demogr.mpg.de> wrote: >>> Dear all, >>> >>> let's assume I have a vector of character strings: >>> >>> x <- c("abcdef", "defabc", "qwerty") >>> >>> What I would like to find is the following: all elements where the word >>> 'abc' does not appear (i.e. 3 in this case of 'x'). >>> >>> Since I am not really experienced with regular expressions, I started >>> slowly and thought I find all word were 'abc' actually does appear: >>> >>>> grep(pattern="abc", x=x) >>> [1] 1 2 >>> >>> So far, so good. Now I read that ^ is the negation operator. But it can >>> also denote the beginning of a string as in: >>> >>>> grep(pattern="^abc", x=x) >>> [1] 1 >>> >>> Of course, we need to put it inside square brackets to negate the >>> expression [1] >>>> grep(pattern="[^abc]", x=x) >>> [1] 1 2 3 >>> >>> But this is not what I want either. >>> >>> I'd appreciate any help. I assume this is rather easy and >>> straightforward. >>> >>> Thanks, >>> Roland >>> >>> >>> [1] http://www.zytrax.com/tech/web/regex.htm: The ^ (circumflex or >>> caret) inside square brackets negates the expression.... >>> >>> ---------- >>> This mail has been sent through the MPI for Demographic Research. Should >>> you receive a mail that is apparently from a MPI user without this text >>> displayed, then the address has most likely been faked. If you are >>> uncertain >>> about the validity of this message, please check the mail header or ask >>> your >>> system administrator for assistance. >>> >>> ______________________________________________ >>> 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.
