Bayesian Additive Regression Trees with Ridge Function Outputs // Implements an extension of Bayesian Additive Regression Trees (BART) in which each regression tree outputs a linear combination of random ridge functions (i.e., a composition of a non-linear function like cosine, hyperbolic tangent, the rectified linear unit with an affine transformation) instead of a constant. Can be used to perform "targeted smoothing" in which trees split on certain covariates but output smooth functions in other covariates. For more information, see Yee, Ghosh, and Deshpande (2026+) doi:10.48550/arXiv.2411.07984.