Exercise

Selecting columns by name

DT[, c("col1", "col2")] returns a data.table with two columns, just like a data.frame.

Alternatively, you can also select columns by passing a list with each element referring to the column name as if it were a variable, i.e., DT[, .(col1, col2)]. Note the absence of quotes, i.e., "" around column names here.

Instructions 1/2

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1
Use a character vector to select the bike_id and trip_id columns (in that order) from batrips.
2
Without using a character vector, select the start_station and end_station columns (in that order) from batrips.