I want to train a Decision Tree model with a dataset, of which some of the continuous variables contain missing values.
I want to preserve the meaning of missing value while training, meaning that I want "NA" (or any value that represents "NA") in continuous variables to show up in the rules of a specific node (if it matters) in the trained model and not just to replace it with medium or other values.
Is there any suggestions as to how should I impute the missing values? I use rpart to build decision tree.
Thank you so much!