Our goals are to provide enhancements to Classification and Regression Tree (CART) software and to create SAS and SYSTAT interfaces on multiple platforms. Enhancements include: (1) a complete Graphical User Interface; (2) a tree-editor for direct visual manipulation of tree-structures including modification of split criteria, and manual pruning and grafting; (3) interactive application of any statistical procedure, including summary statistics procedures, regression, non-linear modelling and high resolution graphics, to the cases passing through a given node; (4) summaries of the copious output of cross-validations to assist users in refining tree-structured analyses, particularly when initial results yield no tree or very shallow trees with low predictive power; (5) addition of Breiman's within-node error measure; (6) incorporation of Boolean splits (and/or combinations of individual splitting rules) into the library of potential splitting rules; (7) extension of the CART algorithms to apply to censored survival data; (8) performance enhancements for single CPU machines and porting CART to run on parallel processing multiple CPU platforms; (9) improving the portability of the source code for different hardware platforms; and finally, (10) the provision of tutorial materials to assist researchers in applying the methodology.
