tree$variable.importance returns NULL with rpart() decision tree

Split from Decision Tree in R rpart() variable importance


**str[quote="KafeelI, post:1, topic:17100, full:true"]
Hello
I was able to get variable importance using iris data in R, using below code

tree=rpart(setosa_dummy~.,data=data,method="class")
tree$variable.importance

But when I tried the same with other data I have. tree$variable.importance returns NULL. Any specific reason for that. I was getting NaN for variable importance using "rf" method in caret. varImp() was used.
[/quote]

How to add simple Cod**

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