Currently I have a problem as follows. In a dataset where multiple observations for each subject exist, and I want to make a subset of this dataset where only the maximum data for a record is selected. For example, for a data set as below:
ID <- c(1,1,1,2,2,2,2,3,3)
Value <- c(2,3,5,2,5,8,17,3,5)
Event <- c(1,1,2,1,2,1,2,2,2)
group <- data.frame(Subject=ID, pt=Value, Event=Event)
Subject 1, 2 and 3 have the biggest pt value of 5, 17 and 5 respectively. How could I first, find the biggest pt value for each subject, and then, put this observation in another data frame? This means that this subset would only have the biggest pt values for each subject.