代码是：
D3<- read.csv("MOOC1.csv", head=TRUE)
cer_ctree <- rpart(certified~forum.posts+grade+assignment,data=D3,method="class",parms = list(split="gini"))
cer_ctree


结果是：
n= 1000

node), split, n, loss, yval, (yprob)
      * denotes terminal node

1) root 1000 204 yes (0.2040000 0.7960000) *


源数据为：