Refinement and selection heuristics in subgroup discovery and classification rule learning

Classification rules and rules describing interesting subgroups are important components of descriptive machine learning. Rule learning algorithms typically proceed in two phases: rule refinement selects conditions for specializing the rule, and rule selection selects the final rule among several rule candidates. While most conventional algorithms use the same heuristic for guiding both phases, recent research indicates that the use of two separate heuristics is conceptually better justified, improves the coverage of positive examples, and may result in better classification accuracy. The paper presents and evaluates two new beam search rule learning algorithms: DoubleBeam-SD for subgroup discovery and DoubleBeam-RL for classification rule learning. The algorithms use two separate beams and can combine various heuristics for rule refinement and rule selection, which widens the search space and allows for finding rules with improved quality. In the classification rule learning setting, the experimental results confirm previously shown benefits of using two separate heuristics for rule refinement and rule selection. In subgroup discovery, DoubleBeam-SD algorithm variants outperform several state-of-the-art related algorithms.