• For more information about the rpart, printcp, and summary functions, please use the help function:

        > ?rpart
        > ?printcp
        > ?summary.rpart  

• C50 is another package that provides a decision tree and a rule-based model. If you are interested in the package, you may refer to the document at http://cran.r-project.org/web/packages/C50/C50.pdf.