Hi group, How can I identify an element with max value among duplicated elements all in a data frame Example: > x1 x1 x2 1 a 4 2 b 3 3 c 2 4 a 1 5 c 2 6 f 3 7 g 4 8 f 5 I want to be able to get a data frame with all unique(x1) with max value x1 x2 1 a 4 2 b 3 3 c 2 5 c 2 7 g 4 8 f 5 Could I get some help please. thanks srini