def _select_best_smooth_at_each_point(self):
for residuals_i in zip(*self._residual_smooths):<EOL><INDENT>index_of_best_span = residuals_i.index(min(residuals_i))<EOL>self._best_span_at_each_point.append(DEFAULT_SPANS[index_of_best_span])<EOL><DEDENT>
Solve Eq (10) to find the best span for each observation.

Stores index so we can easily grab the best residual smooth, primary smooth, etc.