The function leans on attributes of the data that are
provided by the create_dyadyear()
or create_stateyear()
function. Make sure that function (or data created by that function)
appear at the top of the proverbial pipe.
The data returned will also have a new column called duplicated
.
Thus, an implicit assumption in this function is the user does not have
a column in the data with this name that is of interest to the user.
It will be overwritten.