How to select the row with the maximum value in each group

Question

In a dataset with multiple observations for each subject I want to take a subset with only the maximum data value for each record. For example, with a following dataset:

Answer 1

In base you can use ave to get max per group and compare this with pt and get a logical vector to subset the data.frame.

group[group$pt == ave(group$pt, group$Subject, FUN=max),]
#  Subject pt Event
#3       1  5     2
#7       2 17     2
#9       3  5     2

Or compare it already in the function.

group[as.logical(ave(group$pt, group$Subject, FUN=function(x) x==max(x))),]
#group[ave(group$pt, group$Subject, FUN=function(x) x==max(x))==1,] #Variant
#  Subject pt Event
#3       1  5     2
#7       2 17     2
#9       3  5     2