Figure 2:

Idealized tree in the presence of two predictor variables, X₁ and X₂ with interaction. (A) Different predictor variables are selected on the left and on the right. (B) Splitting stops after the first split on the right but not on the left. (C) The same predictor variable is selected on the left and on the right, but the effect is different. The bars at the bottom of the tree denote the proportion of observations with Y = 0 and Y = 1 in the respective leaves.