On the Selection of the Globally Optimal Prototype Subset for Nearest-Neighbor Classification

Emilio Carrizosa, Belén Martín-Barragán, Frank Plastria, Dolores Romero Morales

Research output: Contribution to journalJournal articleResearchpeer-review


The nearest-neighbor classifier has been shown to be a powerful tool for multiclass classification. We explore both theoretical properties and empirical behavior of a variant method, in which the nearest-neighbor rule is applied to a reduced set of prototypes. This set is selected a priori by fixing its cardinality and minimizing the empirical misclassification cost. In this way we alleviate the two serious drawbacks of the nearest-neighbor method: high storage requirements and time-consuming queries. Finding this reduced set is shown to be NP-hard. We provide mixed integer programming (MIP) formulations, which are theoretically compared and solved by a standard MIP solver for small problem instances. We show that the classifiers derived from these formulations are comparable to benchmark procedures. We solve large problem instances by a metaheuristic that yields good classification rules in reasonable time. Additional experiments indicate that prototype-based nearest-neighbor classifiers remain quite stable in the presence of missing values.
Original languageEnglish
JournalI N F O R M S Journal on Computing
Issue number3
Pages (from-to)470-479
Publication statusPublished - 2007
Externally publishedYes

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