Hi, You could do this either: DF[unlist(with(DF,tapply(B,list(ID),FUN=function(x) x %in% max(x)))),] #or DF[unlist(with(DF,by(B,ID,FUN=function(x) x%in% max(x)))),]
#or library(plyr) DF[ddply(DF,.(ID),summarize,B %in% max(B))[,2],] A.K. Hi, I am struggling with this issue and need some helps. The data set 'DF' includes persons' IDs and other variables A, B, and C. Each Person has multiple values in A, B, and C. What I am trying to do is 1) selecting a maximum value of B within same ID, and 2) making a new data set (DF.2) that select rows aligning with the maximum value of B. DF and DF.2 are below. I've used functions combining which.max, subset, and loop, but it did not work. If you have ideas, please help. > DF ID A B C 1 12 36 2 1 15 30 2 2 56 11 2 2 33 30 2 3 83 23 2 3 58 7 2 4 75 2 2 4 82 36 2 5 77 35 2 5 75 23 2 6 73 10 2 6 76 35 2 7 75 14 2 7 21 30 2 8 14 11 2 8 46 11 2 8 75 11 2 8 30 36 2 9 21 35 2 9 75 23 2 DF.2 ID A B C 1 12 36 2 2 33 30 2 3 83 23 2 4 82 36 2 5 77 35 2 6 76 35 2 7 21 30 2 8 30 36 2 9 21 35 2 Thank you in advance, Lee ______________________________________________ [email protected] 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.
