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# Minimax Learning of Ergodic Markov Chains

*Proceedings of the 30th International Conference on Algorithmic Learning Theory*, PMLR 98:904-930, 2019.

#### Abstract

We compute the finite-sample minimax (modulo logarithmic factors) sample complexity of learning the parameters of a finite Markov chain from a single long sequence of states. Our error metric is a natural variant of total variation. The sample complexity necessarily depends on the spectral gap and minimal stationary probability of the unknown chain, for which there are known finite-sample estimators with fully empirical confidence intervals. To our knowledge, this is the first PAC-type result with nearly matching (up to logarithmic factors) upper and lower bounds for learning, in any metric, in the context of Markov chains.