Computing multiple stats

Let's now combine everything from the past two exercises to find multiple summary statistic with multiple groups in batrips.

Deze oefening maakt deel uit van de cursus

Data Manipulation with data.table in R

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

# Compute mean of duration and total trips grouped by start and end stations
aggregate_mean_trips <- batrips[, ___, ___]
aggregate_mean_trips