Dyads are capable of having multiple disputes in a given year, which can
create a problem for merging into a complete dyad-year data frame.
Consider the case of France and Italy in 1860, which
had three separate dispute onsets that year (MID#0112, MID#0113,
MID#0306), as illustrative of the problem. This merging process employs
several rules to whittle down these duplicate dyad-years for merging
into a dyad-year data frame.
The function will also return a message to the user about the
case-exclusion rules that went into this process. Users who are
interested in implementing their own case-exclusion rules should
look up the "whittle" class of functions also provided in this
package.