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.
Cet exercice fait partie du cours
Data Manipulation with data.table in R
Exercice interactif pratique
Essayez cet exercice en complétant cet exemple de code.
# Add a new column equal to total trips for every start station
batrips[, ___, by = ___]