编写一个函数来绘制R中的决策树

Question

我写了这个函数：

dec.Tree <- function(subject, formula, dfName, treePackage) {
if(treePackage == tree) library(tree)
if(treePackage == tree) churn.tree <- tree(subject ~ formula, dfName)
if(treePackage == tree) plot(churn.tree, main ="Churn Tree using tree package")
if(treePackage == tree) text(churn.tree)
}

当我运行功能代码时，它创建函数没问题，但是当我使用代码调用函数时..

dec.Tree(Churn, ., cust.Churn, tree)

它返回错误消息：

  

treePackage == tree中的错误：compare（1）仅适用于   原子和列表类型