Adding multiple columns (I)
More often than not, you may want to add/update multiple columns by reference. There are two ways to do this in data.table:
- LHS := RHS form
- Functional form
In this exercise, you will add columns using the LHS := RHS form. In the LHS, you specify column names as a character vector and in the RHS, you specify values/expressions to be added inside list() (or the alias, .()).
Cet exercice fait partie du cours
Data Manipulation with data.table in R
Instructions
Add two new columns (mean_duration and median_duration) by reference using the LHS := RHS form that calculates the mean and median of the duration column for every start_station.
Exercice interactif pratique
Essayez cet exercice en complétant cet exemple de code.
# Add columns using the LHS := RHS form
batrips[, ___,
by = start_station]