4 packages on CRAN
Build regression models using the techniques in Friedman's papers "Fast MARS" and "Multivariate Adaptive Regression Splines". (The term "MARS" is trademarked and thus not used in the name of the package.)
Plot 'rpart' models. Extends plot.rpart() and text.rpart() in the 'rpart' package.
Plot model surfaces for a wide variety of models using partial dependence plots and other techniques. Also plot model residuals and other information on the model.
Plot principal component histograms around a bivariate scatter plot.