Hi R users, I have a dataframe, where there is a column 'time' represents time series but is not complete. How to expand the dataframe so this column will become complete, where other columns with the newly added rows have NA values? Thanks. df A B C time 10 5 3.3 1990-01-01 11 5 4 1990-02-07 12 4 3 1990-02-14 ... [[alternative HTML version deleted]]