Fuzzy-Rough Set Bireducts for Data Reduction

Data reduction is an important step that helps ease the computational intractability for learning techniques when data are large. This is particularly true for the huge datasets that have become commonplace in recent times. The main problem facing both data preprocessors and learning techniques is that data are expanding both in terms of dimensionality and also in terms of the number of data instances. Approaches based on fuzzy-rough sets offer many advantages for both feature selection and classification, particularly for real-valued and noisy data; however, the majority of recent approaches tend to address the task of data reduction in terms of either dimensionality or training data size in isolation. This paper demonstrates how the notion of fuzzy-rough bireducts can be used for the simultaneous reduction of data size and dimensionality. It also shows how bireducts and, therefore, reduced subtables of data can be used not only as a preprocessing tool but also for the learning of compact and robust classifiers. Furthermore, the ideas can also be extended to the unsupervised domain when dealing with unlabeled data. Experimental evaluation of various techniques demonstrate that high levels of simultaneous reduction of both dimensionality and data size can be achieved whilst maintaining robust performance.