Thanks for suggestions. I suspect the "regexpr" version will be better than my version, since I use it to find an string towards the end of a large (up to ~30Mb) test/XML file.
Thanks again. Jarek ====================================================\==== Jarek Tuszynski, PhD. o / \ Science Applications International Corporation <\__,| (703) 676-4192 "> \ [EMAIL PROTECTED] ` \ -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Prof Brian Ripley Sent: Thursday, September 15, 2005 10:43 AM To: Barry Rowlingson Cc: [email protected] Subject: Re: [R] Splitting the string at the last sub-string On Thu, 15 Sep 2005, Barry Rowlingson wrote: > Prof Brian Ripley wrote: > >>> substring(str, c(1, 26), c(25,length(str))) > > nchar(str) surely? Yes, or anything larger: I actually tested 10000. > regexps can be rather slow though. Here's two functions: But that's not the way to do this repeatedly for the same pattern. (It is normally compiling regexps that is slow, and regexpr is vectorized.) Not that I would call 300us `slow'. > byRipley = > function(str,sub){ > lp=attr(regexpr(paste(".*",sub,sep=""),str),'match.length') > return(substring(str, c(1, lp+1), c(lp,nchar(str)))) } > > byJarek = > function(str,sub){ > y = unlist(strsplit(str,sub)) > return(cbind(paste(y[-length(y)], sub, sep="", collapse = ""), > y[length(y)])) > } > > and a quick test: > > > system.time(for(i in 1:100000){byJarek(str,sub)}) > [1] 15.55 0.10 16.06 0.00 0.00 > > > system.time(for(i in 1:100000){byRipley(str,sub)}) > [1] 30.28 0.07 31.86 0.00 0.00 > > Baz > > ______________________________________________ > [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 > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [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 ______________________________________________ [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
