A zero dependency package containing functions to declare labels
and missing values, coupled with associated functions to create (weighted)
tables of frequencies and various other summary measures.
Some of the base functions have been rewritten to make use of the specific
information about the missing values, most importantly to distinguish
between empty NA and declared NA values.
Some functions have similar functionality with the corresponding ones from
packages "haven" and "labelled". The aim is to ensure as much compatibility
as possible with these packages, while offering an alternative in the
objects of class "declared".
