Bivariate decision trees

Decision trees with tests based on a single variable, as produced by methods such as ID3, C4.5 etc., often require a large number of tests to achieve an acceptable accuracy. This makes interpretation of these trees, which is an important reason for their use, disputable. Recently, a number of methods for constructing decision trees with multivariate tests have been presented. Multivariate decision trees are often smaller and more accurate than univariate trees; however, the use of linear combinations of the variables may result in trees that are hard to interpret. In this paper we consider trees with test based on combinations of at most two variables. We show that bivariate decision trees are an interesting alternative to both uni- and multivariate trees.