search for: tp4649855p4650138

Dear list member, I have the following data example ke <- data.frame(patid=c(1,1,1,2,3,3),a=c(1,2,2,1,1,2)) I want to add another variable b, such that the max of 'a' by id is returned i.e data ke becomes ke <- data.frame(patid=c(1,1,1,2,3,3),a=c(1,2,2,1,1,2),b=c(2,2,2,1,2,2)) Any help will be appreciated. Oluwakemi [[alternative HTML version deleted]]