A non-specialized ensemble classifier using multi-objective optimization

Abstract

Ensemble classification algorithms are often designed for data with certain properties, such as imbalanced class labels, a large number of attributes, or continuous data. While high-performing, these algorithms sacrifice performance when applied to data outside the targeted domain. We propose a non-specific ensemble classification algorithm that uses multi-objective optimization instead of relying on heuristics and fragile user-defined parameters. Only two user-defined parameters are included, with both being found to have large windows of values that produce statistically indistinguishable results, indicating the low level of expertise required from the user to achieve good results. Additionally, when given a large initial set of trained base-classifiers, we demonstrate that a multi-objective genetic algorithm aiming to optimize prediction accuracy and diversity will prefer particular types of classifiers over others. The total number of chosen classifiers is also surprisingly small – only 10.14 classifiers on average, out of an initial pool of 900. This occurs without any explicit preference for small ensembles of classifiers. Even with these small ensembles, significantly lower empirical classification error is achieved compared to the current state-of-the-art. © 2020 Elsevier B.V