Exercise

Updating an existing column (II)

In the previous exercise, you updated only one value and you knew the exact location that had to be updated, i.e., the second row of the start_station column. However, in your day-to-day work, you often want to update several values and you won't know the locations in advance.

You can use the filtering expressions in i the same way you did in chapter 1 to update the columns by reference.

In this exercise, you will work with a new data.table, untidy, which is almost identical to batrips, except we randomly introduced some negative values in the duration column.

Instructions

100 XP

Replace all rows where duration is less than 0 with NAs.