Judith: I believe that this is, indeed, tough; it might require PERL regex's to do entirely within the regular expression language. You might also wish to check out the gsubfn package to see if it could help.
However, a reasonably simple alternative approach that I think will work is to use strsplit(): 1. Split on "(" 2. lapply on the resulting list of vectors and remove all elements from each vector that contain a ")" using, e.g. grep(). 3. sapply paste() on the now "cleaned" list to get back the cleaned up strings. I leave it to you to work out details -- or point out why I'm wrong. Alternatively, wait for someone smarter to reply -- which I'm sure will occur given the clarity with which you posed your problem. Cheers, Bert Gunter Genentech Nonclinical Biostatisics -----Original Message----- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Judith Flores Sent: Tuesday, August 25, 2009 1:18 PM To: RHelp Subject: [R] Regular expression to define contents between parentheses Hello dear R-helpers, I haven't been able to figure out of find a solution in the R-help archives about how to delete all the characters contained in groups of parenthesis. I have a vector that looks more or less like this: myvector<-c("something (80 km/h, sd) & more (6 kg/L,sd)", "somethingelse (48 m/s, sd) & moretoo (50g/L , sd)") I want to extract all the strings that are not contained in parenthesis, the goal would be to obtain the following new vector: subvector<-c("something & more", "somethingelse & moretoo") I tried the following, but this pattern seems to enclose all that is included between the first opened parenthesis and the last closed parethesis, which makes sense, but it's not what I need: subvector<-gsub("\\((.*)\\)","",myvector Your help will be very appreciated. Thank you, Judith ______________________________________________ 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.