Classifier-dependent feature selection via greedy methods

The purpose of this study is to introduce a new approach to feature ranking for classification tasks, called in what follows greedy feature selection. In statistical learning, feature selection is usually realized by means of methods that are independent of the classifier applied to perform the prediction using that reduced number of features. Instead, the greedy feature selection identifies the most important feature at each step and according to the selected classifier. The benefits of such scheme are investigated in terms of model capacity indicators, such as the Vapnik-Chervonenkis dimension or the kernel alignment. This theoretical study proves that the iterative greedy algorithm is able to construct classifiers whose complexity capacity grows at each step. The proposed method is then tested numerically on various datasets and compared to the state-of-the-art techniques. The results show that our iterative scheme is able to truly capture only a few relevant features, and may improve, especially for real and noisy data, the accuracy scores of other techniques. The greedy scheme is also applied to the challenging application of predicting geo-effective manifestations of the active Sun.