Angle-Based Hierarchical Classification Using Exact Label Embedding

Abstract

Hierarchical classification problems are commonly seen in practice. However, most existing methods do not fully use the hierarchical information among class labels. In this article, a novel label embedding approach is proposed, which keeps the hierarchy of labels exactly, and reduces the complexity of the hypothesis space significantly. Based on the newly proposed label embedding approach, a new angle-based classifier is developed for hierarchical classification. Moreover, to handle massive data, a new (weighted) linear loss is designed, which has a closed form solution and is computationally efficient. Theoretical properties of the new method are established and intensive numerical comparisons with other methods are conducted. Both simulations and applications in document categorization demonstrate the advantages of the proposed method. Supplementary materials for this article are available online.

KEYWORDS:

• Angle-based large-margin
• Computational efficiency
• Hierarchical classification
• Label embedding

Notes

1 Notes

The dataset is available at http://kt.ijs.si/DragiKocev/PhD/resources/doku.php?id=hmc_classification

Additional information

Funding

Junlong Zhao was supported by National Natural Science Foundation of China (no. 11871104). Xiaoling Lu’s research was supported by the Ministry of Education Focus on Humanities and Social Science Research Base (Major Research Plan 17JJD910001), and fund for building world-class universities (disciplines) of Renmin University of China. Yufeng Liu’s research was supported in part by NSF grants IIS-1632951, DMS-1821231, and NIH grant R01GM126550.