Non-exchangeability in Infinite Switching Linear Dynamical Systems

Complex nonlinear time-series data can be effectively modeled by Switching Linear Dynamical System (SLDS) models. In trying to allow for unbounded complexity in the discrete modes, most approaches have focused on Dirichlet Process mixture models. Such non-parametric Bayesian models restrict the distribution over dynamical modes to be exchangeable, making it difficult to capture important temporally and spatially sequential dependencies. In this work, we address these concerns by developing the non-exchangeable SLDS (neSLD) model class effectively extending infinite-capacity SLDS models to capture non-exchangeable distributions over dynamical mode partitions. Importantly, from this non-exchangeability, we can learn transition probabilities with infinite capacity that depend on observations or on the continuous latent states. We leverage partial differential equations (PDE) in the modeling of latent sufficient statistics to provide a Markovian formulation and support efficient dynamical mode updates. Finally, we demonstrate the flexibility and expressivity of our model class on synthetic data.