Nadaraya–Watson estimator
= Nadaraya–Watson estimator
{c}
= Local constant estimator
{synonym}
This local-constant estimator is one particular <kernel regression> method.
The Nadaraya–Watson estimator is the degree-zero local polynomial estimate
$$
\widehat m(x)=
\frac{\sum_iK((x_i-x)/h)Y_i}
{\sum_iK((x_i-x)/h)}.
$$
At a support boundary it generally has first-order bias because it reproduces constants but not linear functions.