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.
Este exercício faz parte do curso
Data Manipulation with data.table in R
Exercício interativo prático
Experimente este exercício completando este código de exemplo.
# Add a new column equal to total trips for every start station
batrips[, ___, by = ___]