numeric, non-negative integer, less than number of
legislators represented in obj. Roll calls with lop
or fewer legislators voting in the minority are dropped. Default is
0, meaning that unanimous votes are dropped.
Value
A rollcall object or a link{matrix} depending on
the class of object.
Details
See documentation for specific methods. Unanimous votes are the
equivalent of test items that all subjects score correct (or
all subjects scores incorrect); since there is no variation
among the legislators/subjects, these votes/items provide no
information as to latent traits (ideology, preferences, ability). A
reasonably large number of rollcalls in any contemporary U.S. Congress
are unanimous.