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Search-based Class Discretization

Luís Torgo

email : ltorgo@liacc.up.pt

João Gama

email : jgama@liacc.up.pt

LIACC - University of Porto
R. Campo Alegre, 823 - 4150 Porto - Portugal

Phone : (+351) 2 6001672 Fax : (+351) 2 6003654

WWW : http://www.liacc.up.pt/liacc/ML

Abstract. We present a methodology that enables the use of classification algorithms on regression tasks. We implement this method in system RECLA that transforms a regression problem into a classification one and then uses an existent classification system to solve this new problem. The transformation consists of mapping a continuous variable into an ordinal variable by grouping its values into an appropriate set of intervals. We use misclassification costs as a means to reflect the implicit ordering among the ordinal values of the new variable. We describe a set of alternative discretization methods and, based on our experimental results, justify the need for a search-based approach to choose the best method. Our experimental results confirm the validity of our search-based approach to class discretization, and reveal the accuracy benefits of adding misclassification costs.

Keywords : Regression, Classification, Discretization methods.



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