Classification Trees for Ordinal Variables

We introduce newcriteria to obtain classification trees for ordinal response variables. At this aim, Breiman et al. (Classification and regression trees.Wadsworth, Belmont, 1984), extended their twoing criterion to the ordinal case. Following CART procedure, we extend the well known Gini–Simpson criterion to the ordinal case. Referring to the exclusivity preference property (introduced byTaylor and Silverman in Stat Comput 3:147–161, 1993, for the nominal case), suitably modified for the ordinal case, a second criterion is introduced. The hereby proposed methods are compared with the ordered twoing criterion via simulations.