oO(ML Discuss)
We study an instance of high-dimensional statistical inference in which the goal is to use $N$ noisy observations to estimate a matrix $\Theta^* \in \real^{k \times p}$ that is assumed to be either exactly low rank, or near'' low-rank, meaning that it can be well-approximated by a matrix with low rank. We consider an $M$-estimator based on regularization by the trace or nuclear norm over matrices, and analyze its performance under high-dimensional scaling. We provide non-asymptotic bounds on the Frobenius norm error that hold for a general class of noisy observation models, and apply to both exactly low-rank and approximately low-rank matrices. We then illustrate their consequences for a number of specific learning models, including low-rank multivariate or multi-task regression, system identification in vector autoregressive processes, and recovery of low-rank matrices from random projections. Simulations show excellent agreement with the high-dimensional scaling of the error predicted by our theory.