Graph-based approaches for over-sampling in the context of ordinal regression

Research output: Contribution to journalArticle


  • María Pérez-Ortiz
  • Pedro Antonio Gutiérrez
  • César Hervás-Martínez
  • Xin Yao

Colleges, School and Institutes

External organisations

  • University of Córdoba


The classification of patterns into naturally ordered labels is referred to as ordinal regression or ordinal classification. Usually, this classification setting is by nature highly imbalanced, because there are classes in the problem that are a priori more probable than others. Although standard over-sampling methods can improve the classification of minority classes in ordinal classification, they tend to introduce severe errors in terms of the ordinal label scale, given that they do not take the ordering into account. A specific ordinal over-sampling method is developed in this paper for the first time in order to improve the performance of machine learning classifiers. The method proposed includes ordinal information by approaching over-sampling from a graph-based perspective. The results presented in this paper show the good synergy of a popular ordinal regression method (a reformulation of support vector machines) with the graph-based proposed algorithms, and the possibility of improving both the classification and the ordering of minority classes. A cost-sensitive version of the ordinal regression method is also introduced and compared with the over-sampling proposals, showing in general lower performance for minority classes.


Original languageEnglish
Article number6940273
Pages (from-to)1233-1245
Number of pages13
JournalIEEE Transactions on Knowledge and Data Engineering
Issue number5
Publication statusPublished - 1 May 2015


  • imbalanced classification, ordinal classification, ordinal regression, Over-sampling