Bm Definition am Variable descriptor BF4 0.7615-Histidine 3.49646 Histidine BF6 Citrulline-0.338 6.6434 Citrulline BF10 Citrulline-0.49 -7.00747 Citrulline BF13 Lysine-1.401 0.121036 Lysine BF18 Arginine-2.719 -0.104259 Arginine ( y)+ = max(0,y)

Table 6: MARS Basis Functions. Shown are the basis functions (BF) for the MARS model of PUD prediction. Bm, each individual basis function, am, coefficient of the basis function.