Type Model specification Model specification
GLM GAM
Interaction rC × rG f(rC) × f(rG)
Combination rC + rG f(rC) + f(rG)
Single variable (C. d) rC f(rC)
Single variable (G. f) rG f(rG)
Parametric term (C. d) f(rC) + rG
Parametric term (G. f) f(rG) + rC