Summary data by column in R

Question

I have the following data

pt_id <- c(1,1,1,1,1,2,2,2,3,3,3,3,3,4,4,4,4)
Tob_pk <- c(2, 5, 7, 1, 8, 12, 14, 3, 6, 8, 10, 20, 13, 5, 4, 12, 10)
Tobacco &l