I need help with fitting 3 differential equations for 3 regimens within the same study. I want to switch between models for the 3 regimens Can I use if statements to do so? For example, If id=1 deriv(E = EKin - Kout * E) else deriv(E = EKin - (1+Cp*Emax/Cp+EC50)RKout * E) endif Thanks, Vaishali