Decision Tree Basics

r tree basic.r

# *------------------------------------------------------------------
# | PROGRAM NAME: R_tree_basic 
# | DATE:4/26/11    
# | CREATED BY: Matt Bogard 
# | PROJECT FILE:P:\R  Code References\Data Mining_R              
# *----------------------------------------------------------------
# | PURPOSE: demo of basic decision tree mechanics               
# | To support post: http://econometricsense.blogspot.com/2012/01/decision-tree-basics-in-sas-and-r.html 
# *------------------------------------------------------------------
 
rm(list=ls()) # get rid of any existing data 
ls() # view open data sets
 
setwd('/Users/wkuuser/Desktop/R Data Sets') # mac 
setwd("P:\\R  Code References\\R Data") # windows
 
library(rpart) # install rpart decision tree library
 
# *------------------------------------------------------------------
# | get data            
# *-----------------------------------------------------------------
 
dat1 <-  read.csv("basicTree.csv", na.strings=c(".", "NA", "", "?"), encoding="UTF-8")
plot( dat1$x2, dat1$x1, col = dat1$class) # plot data space
 
# fit decision tree
 
(r <- rpart(class ~ x1 + x2, data = dat1)) 
 
plot(r)
text(r)
 
library(rattle) # data mining package
drawTreeNodes(r) # for more detailed tree plot supported by rattle