Sorry,I miss a word:"If I wanna calculate each group's mean extra"
2011/8/16 Lao Meng <laomen...@gmail.com> > Hi all: > My data:data(sleep) > > If I wanna calculate each group's extra,what I can do is: > #method1 > attach(sleep) > mean(extra[group==1]) > mean(extra[group==1]) > > > #method2 > result<-matrix(,0,2) > g<-split(sleep,sleep$group) > for(i in 1:length(g)) > { > result<-rbind(result,data.frame(unique(g[[i]]$group),mean(g[[i]]$extra))) > } > colnames(result)<-c("name","mean") > > But the above 2 method is a little bit tedious.Is there a "short cut" > manner to get the same result? > > Thanks a lot! > > My best > [[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.