Adaptive Local Linear Regression with Application to Printer Color Management

摘要

Local learning methods, such as local linear regression and nearest neighbor classifiers, base estimates on nearby training samples, neighbors. Usually the number of neighbors used in estimation is fixed to be a global 'optimal' value, chosen by cross-validation. This paper proposes adapting the number of neighbors used for estimation to the local geometry of the data, without need for cross-validation. The term enclosing neighborhood is introduced to describe a set of neighbors whose convex hull contains the test point when possible. It is proven that enclosing neighborhoods yield bounded estimation variance under some assumptions. Three such enclosing neighborhood definitions are presented: natural neighbors, natural neighbors inclusive, and enclosing kappa-NN. The effectiveness of these neighborhood definitions with local linear regression is tested for estimating look-up tables for color management. Significant improvements in error metrics are shown, indicating that enclosing neighborhoods may be a promising adaptive neighborhood definition for other local learning tasks as well, depending on the density of training samples.