We consider the binary classification of imbalanced data. A dataset is imbalanced if the proportion of classes are heavily skewed. Imbalanced data classification is often challengeable, especially for high-dimensional data, because unequal classes deteriorate classifier performance. Under sampling the majority class or oversampling the minority class are popular methods to construct balanced samples, facilitating classification performance improvement. However, many existing sampling methods cannot be easily extended to high-dimensional data and mixed data, including categorical variables, because they often require approximating the attribute distributions, which becomes another critical issue. In this paper, we propose a new sampling strategy employing raking and relabeling procedures, such that the attribute values of the majority class are imputed for the values of the minority class in the construction of balanced samples. The proposed algorithms produce comparable performance as existing popular methods but are more flexible regarding the data shape and attribute size. The sampling algorithm is attractive in practice, considering that it does not require density estimation for synthetic data generation in oversampling and is not bothered by mixed-type variables. In addition, the proposed sampling strategy is robust to classifiers in the sense that classification performance is not sensitive to choosing the classifiers.

Measuring data utility and privacy risk embedded in synthetic or other de-identified datasets is an increasingly important research area. Existing measures in the data privacy literature however are one-sided in that they either measure utility or privacy risk only. In this paper we propose a new measure that can evaluate both data utility and privacy, a well-known trade-off relationship in data synthesis. The proposed measure employs the notion of relative distance between the synthetic and original datasets at the dataset level, and can identify the optimally balanced position of the synthetic data in terms of both utility and privacy. In addition, we devise a graphical tool that visually reveals the current utility-privacy trade-off position of the synthetic data. Numerical studies show our new measure consistently performs better and offers richer interpretations than other existing global data utility measures, for both simulated and real datasets, confirming its distinctive advantages.

The performance of a classification model significantly depends on the degree to which the support of each data class overlaps. Successfully distinguishing classes is difficult if the support is similar while classes differ. In the one-class classification (OCC) problem, wherein the data comprise only a single class, classifier performance is significantly degraded if the population support of each class is similar. In this study, we propose a preprocessing algorithm that enhances classifier performance by utilizing macro information that is most easily obtainable in these two problem situations. The algorithm aims to improve classifier performance by reprocessing the given data into data with mitigated class imbalance through raking and sampling techniques. This improvement in performance is demonstrated by comparing representative classifiers used in the existing OCC problem with traditional binary classifier models, unavailable on the single-class dataset.