And if you are extremely concerned with speed, do not compute a$b and a$c in every iteration of the loop. E.g., change lapply(seq_along(a$c),function(x) a$b[x]-a$c[[x]]) to something like with(a, lapply(seq_along(c), function(x)b[x] - c[[x]]))
Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On > Behalf > Of R. Michael Weylandt > Sent: Thursday, August 09, 2012 4:22 PM > To: arun > Cc: R help; jimi adams > Subject: Re: [R] indexing in data frames > > On Thu, Aug 9, 2012 at 5:30 PM, arun <smartpink...@yahoo.com> wrote: > > > > lapply(1:length(a$c),function(x) a$b[x]-a$c[[x]]) > > Arun, > > I've seen you use this idiom a few times lately and I'd just like to note that > > seq_along() > > is an (underutilized) primitive and a safer and faster alternative > (avoiding the pathological length(x) = 0 case). > > Cheers, > Michael > > ______________________________________________ > 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.
