Duplicates in the original directed dyad-year alliance data were
pre-processed. Check cow_alliance
in the package's data-raw
directory on Github for more information.
This function will also work with leader-dyad-years, though users should be
careful with leader-level applications of alliance data. Alliance data are
primarily communicated yearly, making it possible---even likely---that at
least one leader-dyad in a given year is credited with an alliance that was
not active in the particular leader-dyad. The Correlates of War's alliance
data are not communicated with time measurements more granular than the year.
Apply these data to leader-level analyses with that in mind.