> -----Original Message----- > From: r-help-boun...@r-project.org > [mailto:r-help-boun...@r-project.org] On Behalf Of yjmha69 > Sent: Friday, June 04, 2010 12:28 PM > To: R-help@r-project.org > Subject: [R] subsetting a dataframe > > Hi there, > > a<-data.frame(c(1,2,2,5,9,9),c("A","B","C","D","E","F")) > > names(a)<-c("x1","x2") > > max(table(a$x1)) > [1] 2 > > > The above shows the max count for x1 is 2, which is correct. > But we can't tell > there are 2 groups that meet this criteria: 2,2 and 9,9. > I then want to extract the records that has the hightest count > > a[max(table(a$x1)),] > x1 x2 > 2 2 B > This is not working, since it is equvalent to a[2,] > What I want is > x1 x2 > 2 2 B > 3 2 C > 5 9 E > 5 9 F > > I think this should be very easy, but I'm a beginner :-)
One way is to use merge to combine your table with the original data.frame: > tmp <- merge(a, as.data.frame(table(a$x1)), by.x="x1", by.y="Var1") > tmp[tmp$Freq==max(tmp$Freq), ,drop=FALSE] Another way is to use ave: > tmp <- with(a, ave(x1, x1, FUN=length)) > a[tmp==max(tmp), , drop=FALSE] Another way is > a[as.character(a$x1) %in% names(tmp[tmp==max(tmp)]), , drop=FALSE] (This last one might have problems when some values in a$x1 are different but so close that as.character() makes the same string out of them.) Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > > Thanks > > YJM > > > > > > ______________________________________________ > 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.
