Rough set theory and multi objective evolutionary algorithm based undersampling and oversampling framework towards class imbalance problem

doi:10.1007/s11042-025-21082-9

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Rough set theory and multi objective evolutionary algorithm based undersampling and oversampling framework towards class imbalance problem

2025-08-13

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Mehwish Naushin

Asit Kumar Das

DOI：10.1007/s11042-025-21082-9

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Abstract

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The paper explores the class imbalance problem in classification models which show bias towards the majority class and perform poorly for the minority class. The proposed approach combines Rough Set Theory (RST) and Evolutionary Algorithm (EA) to create an innovative resampling framework. Undersampling is achieved by removing ambiguous majority class samples from the boundary region of the rough set. In oversampling, synthetic minority samples are generated in the positive region applying EAs guided by Kullback-Leibler (KL) divergence and Attribute Dependency (AD) based two objective functions. RST improves the class boundary clarity by filtering out ambiguous majority samples. In contrast, AD ensures that the generated synthetic samples retain feature similarity and align closely with the distribution of minority samples in the positive region. KL divergence further refines the process by reducing the distributional gap between the original and synthetic minority samples. Experiments on well-known datasets indicate that the novel framework improves class balance and classification performance by effectively reducing bias towards the majority class. As a result, we get better generalization and improve minority class recognition. The proposed method has been validated with the comparative analysis of existing resampling techniques, which invariably gives better performance in accuracy, F-score and other measures, albeit with a slight increase in time complexity. The method has potential applications in various real-world classification tasks.

Keywords:

Rough set theory

Multi-objective evolutionary algorithms

Region of uncertainty

Class imbalance problem

Entropy and information theory