How to Bin or Convert Numerical Variables to Categorical Variables with Decision Trees

Why would you want to convert a numerical variable into categorical one? Depending on the situation, it can lead to a better interpretation of the numerical variable, quick segmentation or just an additional feature for building your predictive model by creating bins for the numerical variable. Binning is a popular feature engineering technique. Suppose your hypothesis is that the age of a customer is correlated with their tendency to interact with a mobile app. The age of the user is plotted on x-axis and user interaction with the app is plotted on the y-axis.