How large is your dataframe? How much memory do you have on your system? Are you paging? Here is a test I ran with a data frame with 1,000,000 entries and it seems to be fast:
> n <- 1000000 > x <- data.frame(A=sample(LETTERS,n,TRUE), B=sample(letters[1:4],n,TRUE), + C=sample(LETTERS[1:4], n, TRUE), data=runif(n)) > system.time(x.agg <- aggregate(x$data, list(x$A, x$B, x$C), mean)) user system elapsed 2.65 0.34 3.00 > On Jan 26, 2008 6:45 PM, zhihuali <[EMAIL PROTECTED]> wrote: > > Hi, netters, > > First of all, thanks a lot for all the prompt replies to my earlier question > about "merging" data frames in R. > Actually that's an equivalence to the "join" clause in mysql. > > Now I have another question. Suppose I have a data frame X with lots of > columns/variables: > Name, Age,Group, Type, Salary. > I wanna do a subtotal of salaries: > aggregate(X$Salary, by=list(X$Group,X$Age,X$Type),Fun=mean) > > When the levels of Group and Type are huge, it took R forever to finish the > aggregation. > And I used gc to find that the memory usage was big too. > > However, in mysql, it took seconds to finish a similar job: > select Group,Age,Type ,avg(Salary) from X group by Group,Age,Type > > Is it because mysql is superior in doing such kind of things? Or my R command > is not efficient enough? Why did R have to consume huge memories to do the > aggregation? > > Thanks again! > > Zhihua Li > > _________________________________________________________________ > 天凉了，添衣了，心动了，"七件"了 > http://get.live.cn > [[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. > > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ 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.
