add_group_sub           Add sub index within group
extract_col             Helper for na_col_omit()
has_col                 Detect if df has col
hogwarts                Timetable in Hogwarts School of Witchcraft and
                        Wizardry.
na2empty                replace NA character into ""
omit_na_cols            Remove all NA cols
omit_na_rows            Remove all NA rows
pivot                   Pivot easily by specifying rows, columns,
                        values and split.
replace_col             Replace a col with a data.frame.
split_force             Split by force with "" when split is NULL
validate_col            Validate col
