When Neighbors Tie - k-NN and Boundaries

A nearest-neighbor vote can end with equal class counts. This lesson shows an exact tied vote and names the required policy boundary.

highlighted = computed this step

Four nearest rows

This shown query uses k=4. The four displayed nearest rows have squared distances 1, 1, 4, and 4.

k=4,\quad d^2=[1,1,4,4]

Among those neighbors, class A has 2 votes and class B has 2 votes. No class wins from the vote alone.

A:2,\quad B:2

Because the vote is tied, the displayed output is tie policy required. A class label would need a stated tie policy first.

\text{output}=\text{tie policy required}