Each node has a value for each data point 𝑉 4,2 , which is computed to be used as operator arguments on the layer above. The nodal values at the bottom of the tree are determined by the selection of an input variable or a constant. On branch node layers, nodal values are specified by the selected operator in combination with the node values of their children. The allocation of the input predictor variables 𝑥 0,2 is implemented by the binary variables 𝜁