Loss-Based Prior for CART and BART Models

We present a novel prior for tree topology within Bayesian Additive Regression Trees (BART) models. This approach quantifies the hypothetical loss in information and the loss due to complexity associated with choosing the “wrong” tree structure. The resulting prior distribution is compellingly geared toward sparsity — a critical feature considering BART models’ tendency to overfit. Our method incorporates prior knowledge into the distribution via two parameters that govern the tree’s depth and balance between its left and right branches. Additionally, we propose a default calibration for these parameters, offering an objective version of the prior. We demonstrate our method’s efficacy on both simulated and real datasets.