Optionally, unquoted variable names/expressions separated by
commas to be passed to dplyr::select(). Otherwise, all columns are
included.
by.wave
(if skimr is installed) Separate descriptives by wave?
Default is TRUE.
by.id
(if skimr is installed) Separate descriptives by entity?
Default is FALSE. Be careful if you have a large number of entities as
the output will be massive.