Optimization of Hierarchical Regression Model with Application to Optimizing Multi-Response Regression K-ary Trees

A fast, convenient and well-known way toward regression is to induce and prune a binary tree. However, there has been little attempt toward improving the performance of an induced regression tree. This paper presents a meta-algorithm capable of minimizing the regression loss function, thus, improving the accuracy of any given hierarchical model, such as k-ary regression trees. Our proposed method minimizes the loss function of each node one by one. At split nodes, this leads to solving an instance-based cost-sensitive classification problem over the node’s data points. At the leaf nodes, the method leads to a simple regression problem. In the case of binary univariate and multivariate regression trees, the computational complexity of training is linear over the samples. Hence, our method is scalable to large trees and datasets. We also briefly explore possibilities of applying proposed method to classification tasks. We show that our algorithm has significantly better test error compared to other state-ofthe- art tree algorithms. At the end, accuracy, memory usage and query time of our method are compared to recently introduced forest models. We depict that, most of the time, our proposed method is able to achieve better or similar accuracy while having tangibly faster query time and smaller number of nonzero weights.