This function figures out which rows are missing in either state and applies
the provided enter and exit functions to fill in the blanks and provide
a 1-to-1 relation between the rows in from and to.
.complete_states(from, to, id, enter, exit, max_id)Data.frames to tween between
The name of the column that holds the matching id
functions to fill out missing rows in from and to
respectively
A list with the elements from and to holding the filled out
versions of from and to