Evaluation and optimization of frequent, closed and maximal association rule based classification

Abstract

Real world applications of association rule mining have well-known problems of discovering a large number of rules, many of which are not interesting or useful for the application at hand. The algorithms for closed and maximal itemsets mining significantly reduce the volume of rules discovered and complexity associated with the task, but the implications of their use and important differences with respect to the generalization power, precision and recall when used in the classification problem have not been examined. In this paper, we present a systematic evaluation of the association rules discovered from frequent, closed and maximal itemset mining algorithms, combining common data mining and statistical interestingness measures, and outline an appropriate sequence of usage. The experiments are performed using a number of real-world datasets that represent diverse characteristics of data/items, and detailed evaluation of rule sets is provided as a whole and w.r.t individual classes. Empirical results confirm that with a proper combination of data mining and statistical analysis, a large number of non-significant, redundant and contradictive rules can be eliminated while preserving relatively high precision and recall. More importantly, the results reveal the important characteristics and differences between using frequent, closed and maximal itemsets for the classification task, and the effect of incorporating statistical/heuristic measures for optimizing such rule sets. With closed itemset mining already being a preferred choice for complexity and redundancy reduction during rule generation, this study has further confirmed that overall closed itemset based association rules are also of better quality in terms of classification precision and recall, and precision and recall on individual class examples. On the other hand maximal itemset based association rules, that are a subset of closed itemset based rules, show to be insufficient in this regard, and typically will have worse recall and generalization power. Empirical results also show the downfall of using the confidence measure at the start to generate association rules, as typically done within the association rule framework. Removing rules that occur below a certain confidence threshold, will also remove the knowledge of existence of any contradictions in the data to the relatively higher confidence rules, and thus precision can be increased by disregarding contradictive rules prior to application of confidence constraint.