(Builds on: Tidy data, Regular expressions)
tidyr::separate() is a useful tool for handling another common type of
messiness: when multiple variables are crammed into a single column.
Here you’ll learn how to use separate() to pull them out into their own
columns.
The sep argument to separate() is a regular expression, which gives
you a lot of power. extract() is similar. str_split() is to separate()
as str_match() is to extract().
The inverse of separate() is unite(). You use it when you have a variable
that is spread across multiple columns. This happens much less commonly.