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. > [[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.
