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Inference-less Density Estimation using Copula Networks
Proceedings of the 26th Conference on Uncertainty in Artificial Intelligence, PMLR R8:167-175, 2010.
Abstract
We consider learning continuous probabilistic graphical models in the face of missing data. For non-Gaussian models, learning the parameters and structure of such models depends on our abil- ity to perform efficient inference, and can be pro- hibitive even for relatively modest domains. Re- cently, we introduced the Copula Bayesian Net- work (CBN) density model - a flexible frame- work that captures complex high-dimensional dependency structures while offering direct con- trol over the univariate marginals, leading to im- proved generalization. In this work we show that the CBN model also offers significant computa- tional advantages when training data is partially observed. Concretely, we leverage on the spe- cialized form of the model to derive a compu- tationally amenable learning objective that is a lower bound on the log-likelihood function. Im- portantly, our energy-like bound circumvents the need for costly inference of an auxiliary distribu- tion, thus facilitating practical learning of high- dimensional densities. We demonstrate the effec- tiveness of our approach for learning the struc- ture and parameters of a CBN model for two real- life continuous domains.