Convex and Nonconvex Formulations for Mixed Regression With Two Components: Minimax Optimal Rates

We consider the mixed regression problem with two components, under adversarial and stochastic noise. We give a convex optimization formulation that provably recovers the true solution, as well as a nonconvex formulation that works under more general settings and remains tractable. Upper bounds are provided on the recovery errors for both arbitrary noise and stochastic noise models. We also give matching minimax lower bounds (up to log factors), showing that our algorithm is information-theoretical optimal in a precise sense. Our results represent the first tractable algorithm guaranteeing successful recovery with tight bounds on recovery errors and sample complexity. Moreover, we pinpoint the statistical cost of mixtures: our minimax-optimal results indicate that the mixture poses a fundamentally more difficult problem in the low-SNR regime, where the learning rate changes.