Combining Feature Subset Selection and Data Sampling for Coping with Highly Imbalanced Software Data

In the software quality modeling process, many practitioners often ignore problems such as high dimensionality and class imbalance that exist in data repositories. They directly use the available set of software metrics to build classification models without regard to the condition of the underlying software measurement data, leading to a decline in prediction performance and extension of training time. In this study, we propose an approach, in which feature selection is combined with data sampling, to overcome these problems. Feature selection is a process of choosing a subset of relevant features so that the quality of prediction models can be maintained or improved. Data sampling seeks a more balanced dataset through the addition or removal of instances. Three different approaches would be produced when combing these two techniques: 1sampling performed prior to feature selection, but retaining the unsampled data instances; 2sampling performed prior to feature selection, retaining the sampled data instances; 3sampling performed after feature selection. The empirical study was carried out on six datasets from a real-world software system. We employed one filter-based (no learning algorithm involved in the selection process) feature subset selection technique called correlationbased feature selection combined with the random undersampling method. The results demonstrate that sampling performed prior to feature selection, but retaining the unsampled data instances (Approach 1) performs better than the other two approaches.