Ranking Based Multitask Learning of Scoring Functions

Scoring functions are an important tool for quantifying properties of interest in many domains; for example, in healthcare, a disease severity scores are used to diagnose the patient’s condition and to decide its further treatment. Scoring functions might be obtained based on the domain knowledge or learned from data by using classification, regression or ranking techniques depending on the type of supervised information. Although learning scoring functions from collected data is beneficial, it can be challenging when limited data are available. Therefore, learning multiple distinct, but related, scoring functions together can increase their quality as shared regularities may be easier to identify. We propose a multitask formulation for ranking-based learning of scoring functions, where the model is trained from pairwise comparisons. The approach uses mixed-norm regularization to impose structural regularities among the tasks. The proposed regularized objective function is convex; therefore, we developed an optimization approach based on alternating minimization and proximal gradient algorithms to solve the problem. The increased predictive accuracy of the presented approach, in comparison to several baselines, is demonstrated on synthetic data and two different real-world applications; predicting exam scores and predicting tolerance to infections score.