A Bayesian Local Causal Discovery Framework

This work introduces the Bayesian local causal discovery framework, a method for discovering unconfounded causal relationships from observational data. It addresses the hypothesis that causal discovery using local search methods will outperform causal discovery algorithms that employ global search in the context of large datasets and limited computational resources.Several Bayesian local causal discovery (BLCD) algorithms are described and results presented comparing them with two well-known global causal discovery algorithms PC and FCI, and a global Bayesian network learning algorithm, the optimal reinsertion (OR) algorithm which was post-processed to identify relationships that under assumptions are causal.Methodologically, this research formalizes the task ofcausal discovery from observational data using a Bayesianapproach and local search. It specifically investigates theso called Y structure in causal discovery andclassifies the various types of Y structurespresent in the data generating networks. Itidentifies the Y structures in the Alarm,Hailfinder, Barley, Pathfinder and Munin networks andcategorizes them. A proof of the convergence of the BLCDalgorithm based on the identification of Y structures, isalso provided. Principled methods of combiningglobal and local causal discovery algorithms to improve uponthe performance of the individual algorithms are discussed. In particular,a post-processing method for identifying plausible causal relationships from the output of global Bayesiannetwork learning algorithms is described, therebyextending them to be causal discovery algorithms.In an experimental evaluation, simulated data fromsynthetic causal Bayesian networks representing fivedifferent domains, as well as a real-world medical dataset, were used. Causal discovery performance was measured using precision and recall.Sometimes the local methods performed better than the global methods,and sometimes they did not (both in terms of precision/recalland in terms of computation time).When all the datasets were considered in aggregate,the local methods (BLCD and BLCDpk) had higher precision.The general performance of the BLCD class of algorithmswas comparable to the global search algorithms, implying that the localsearch algorithms will have good performance onvery large datasets when the global methods fail to scaleup. The limitations of this research and directions for future research are also discussed