You suggested > lapply( lines, function(l) strsplit(l, " // ")[[1]][2] )
strsplit is vectorized so the following is equivalent but simpler and quicker: lapply(strsplit(lines, " // "), function(x)x[2]) The OP probably wants a character vector, not a list so use sapply or vapply (safer than sapply and a bit quicker). Any of the following would do: vapply(strsplit(lines, " // "), `[`, 2, FUN.VALUE="") vapply(strsplit(lines, " // "), function(x)x[2], FUN.VALUE="") sapply(strsplit(lines, " // "), `[`, 2) # wrong answer if length(lines)==0 Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of David Winsemius > Sent: Monday, May 20, 2013 5:17 PM > To: Hon Kit (Stephen) Wong > Cc: [email protected] > Subject: Re: [R] how to GREP out a string like this......THANKS. > > > On May 20, 2013, at 4:45 PM, Hon Kit (Stephen) Wong wrote: > > > Dear ALl, > > > > I hope you could help me out on this simple problem. I have many thousand > > lines like > this: > > NM_019397 // Egfl6 // EGF-like-domain, multiple 6 // X F5|X 71.5 cM // 54156 > > > > I want to extract the string inside the first // //, in this case is Egf16. > > > strsplit("NM_019397 // Egfl6 // EGF-like-domain, multiple 6 // X F5|X 71.5 > > cM // > 54156", split=" // ")[[1]][2] > [1] "Egfl6" > > You can use; > > lapply( lines, function(l) strsplit(l, " // ")[[1]][2] ) > > > > > > > > How do I apply grep function? > > Well, grep is only going to give you a test and you want a replacement or > extraction > function. sub or gsub would be possibilities but they are greedy so its a bit > more difficult > to constrain their targeting to only the first and second "//". > > -- > > David Winsemius > Alameda, CA, USA > > ______________________________________________ > [email protected] 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. ______________________________________________ [email protected] 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.
