I like v <- test[,1] c(TRUE, cumsum( v[-length(v)] != v[-1] )) (R's arithmetic on logicals treats TRUE as 1 and FALSE as 0.)
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 arun > Sent: Thursday, January 24, 2013 3:37 PM > To: Jeffrey Fuerte > Cc: R help > Subject: Re: [R] ifelse to speed up loop? > > HI, > > This might be better. > test$group<-cumsum(abs(c(1,diff(test[,1])))) > A.K. > > > > > ----- Original Message ----- > From: Jeffrey Fuerte <fuert...@vcu.edu> > To: r-help@r-project.org > Cc: > Sent: Thursday, January 24, 2013 4:20 PM > Subject: [R] ifelse to speed up loop? > > Hello, > > I'm not sure how to explain what I'm looking for but essentially I have a > test dataset that looks like this: > > test: > V1 > 1 1 > 2 1 > 3 1 > 4 2 > 5 2 > 6 2 > 7 1 > 8 1 > 9 1 > 10 2 > 11 2 > 12 2 > > And what I want to be able to do is create another column that captures a > "grouping" variable that looks like this: > > test > V1 group > 1 1 1 > 2 1 1 > 3 1 1 > 4 2 2 > 5 2 2 > 6 2 2 > 7 1 3 > 8 1 3 > 9 1 3 > 10 2 4 > 11 2 4 > 12 2 4 > > So, it's keeping track of the changes in V1, but even though V1 could be > the same in different instances, the group is treating it as a new group. > I have written a loop that does what I want, but this takes too long to > run, so I was hoping for either a faster approach or an ifelse statement. > Any ideas? > > By the loop I was using looks like this: > > groupings <- 1 > test$group[1] <- groupings > for (i in 2:length(test$V1)) > { > if (test$V1[i]==test$V1[i-1]) > { > test$group[i] <- groupings > } else { > groupings <- groupings+1 > test$group[i] <- groupings > } > } > > Thanks for the help. > > [[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. > > > ______________________________________________ > 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.
