Adding multiple columns (II)
In this exercise, you will add the same columns as in the previous exercise, using the functional form. In the functional form, you use the colon equal to operator (:=) as a function. Recall that when using operators as functions, they should be wrapped inside backticks, `:=`(). Inside the function call, you pass comma-separated col_name = expression values.
This exercise is part of the course
Data Manipulation with data.table in R
Exercise instructions
Add two new columns (mean_duration and median_duration) by reference using the functional form that calculates the mean and median of the duration column for every start_station.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
# Add columns using the functional form
batrips[, ___,
by = start_station]