Structure estimation for discrete graphical models: Generalized covariance matrices and their inverses

Po-Ling Loh, Martin J. Wainwright

Abstract: We investigate a curious relationship between the structure of a discrete graphical model and the support of the inverse of a generalized covariance matrix. We show that for certain graph structures, the support of the inverse covariance matrix of indicator variables on the vertices of a graph reflects the conditional independence structure of the graph. Our work extends results that have previously been es- tablished only in the context of multivariate Gaussian graphical models, thereby addressing an open question about the significance of the inverse covariance ma- trix of a non-Gaussian distribution. Based on our population-level results, we show how the graphical Lasso may be used to recover the edge structure of cer- tain classes of discrete graphical models, and present simulations to verify our theoretical results.