Adding columns by group
Recall that you can perform computations by group using the by argument of the data.table. In this exercise, you will add new columns by group to the original data.table by reference.
Latihan ini adalah bagian dari kursus
Data Manipulation with data.table in R
Latihan interaktif praktis
Cobalah latihan ini dengan menyelesaikan kode contoh berikut.
# Add a new column equal to total trips for every start station
batrips[, ___, by = ___]