I am using Stata 13 SE and have installed the chaid and chaidforest packages. I have a dataset of patients with ct aortic calcifications labelled ctcal and change in operative strategy labelled opstratch as categorical variables and Age as a continuous variable. I would like to use the chaid decision tree algorithm to determine the significant Age cutoff among patients with ctcal=1(yes) who have had change in op strategy opstratch=1(yes). What syntax should I type in to be able to do this?