Locally Adaptive Nearest Neighbor Algorithms

Four versions of a k-nearest neighbor algorithm with locally adap(cid:173) tive k are introduced and compared to the basic k-nearest neigh(cid:173) bor algorithm (kNN). Locally adaptive kNN algorithms choose the value of k that should be used to classify a query by consulting the results of cross-validation computations in the local neighborhood of the query. Local kNN methods are shown to perform similar to kNN in experiments with twelve commonly used data sets. Encour(cid:173) aging results in three constructed tasks show that local methods can significantly outperform kNN in specific applications. Local methods can be recommended for on-line learning and for appli(cid:173) cations where different regions of the input space are covered by patterns solving different sub-tasks.