Class-specific extreme learning machine based on overall distribution for addressing binary imbalance problem

Class imbalance problem occurs when the training dataset contains significantly fewer samples of one class in contrast to another class. Conventional extreme learning machine (ELM) gives the same importance to all the samples leading to the results, which favor the majority class. To solve this intrinsic deficiency, modifications of ELM have been developed such as weighted ELM (WELM) and WELM based on the overall distribution (ODW-ELM). Recently class-specific ELM (CS-ELM) was designed for class imbalance learning. It has been shown in this work that the derivation of the output weights, beta\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varvec{\beta }$$\end{document}, is more efficient compared to class-specific cost regulation ELM (CCRELM) for handling the class imbalance problem. Motivated by CCRELM, X. Luo et al. have proposed the classifier ODW-ELM, which is also not efficient for imbalance learning. In this work, a novel class-specific ELM based on overall distribution (OD-CSELM) and the kernelized version of OD-CSELM (OD-CSKELM) is proposed to address the binary class imbalance problem more effectively. OD-CSELM and OD-CSKELM are motivated by CS-ELM. In addition, the computational complexity of OD-CSELM and OD-CSKELM is significantly lower than WELM and kernelized WELM, respectively. The proposed work is evaluated by using the benchmark real-world imbalanced datasets. The experimental results demonstrate that the proposed work gives good generalization performance in contrast to the rest of the classifiers for class imbalance learning.

Automated summary

The conventional extreme learning machine (ELM) fails to handle the class imbalance problem effectively because it treats all samples as equally important. To address this issue, modified versions of ELM like weighted ELM (WELM) and overall distribution WELM (ODW-ELM) have been developed. In this study, a class-specific ELM based on overall distribution (OD-CSELM) and its kernelized version (OD-CSKELM) are proposed to handle binary class imbalance problem more effectively. OD-CSELM and OD-CSKELM have lower computational complexity compared to WELM and kernelized WELM, respectively. Experimental results on benchmark datasets demonstrate the superior generalization performance of the proposed methods for class imbalance learning.