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 ejercicio forma parte del curso
Data Manipulation with data.table in R
Ejercicio interactivo práctico
Prueba este ejercicio y completa el código de muestra.
# Add a new column equal to total trips for every start station
batrips[, ___, by = ___]