Thanks all for organizing this series and it was a great learning resource. I submitted a question at the end of webinar and received a reply thereafter from Chris, shown as follows. Thanks for taking care of the question.

__Q: In the structural parameters, we only have CL, but in the fixed effects, we have a, Cl0 and CL, why?__

__A: In the non-static clearance model, Cl is defined as a function of the fixed effects Cl0 and a. It is not a parameter in itself – it is derived from other parameters.__

But still I am little bit confused. When we define Cl = Cl0 - a*C, Cl0 and a are constant parameters and Cl is a variable parameter.

1. Do we have to use stparm to define Cl0 and a as parameters?

2. Is "fixef(tvCl = c(, 4.3, ))" necessary? Cl is dependent on C and therefore changing over time. Should we give it a population mean?

So I am wondering how the model would work with these codes.

test(){

deriv(A1 = - Cl * C - Cl2 * (C - C2) - Cl3 * (C - C3))

deriv(A2 = Cl2 * (C - C2))

deriv(A3 = Cl3 * (C - C3))

dosepoint(A1)

C = A1 / V

C2 = A2 / V2

C3 = A3 / V3

Cl = Cl0 - a * C

error(CEps = 1)

observe(CObs = C * (1 + CEps))

stparm(V = tvV)

stparm(V2 = tvV2)

stparm(V3 = tvV3)

stparm(Cl = tvCl)

**stparm(Cl0 = tvCl0) ## what if we add this?**

**stparm(a = tva) ****## what if we add this?**

stparm(Cl2 = tvCl2)

stparm(Cl3 = tvCl3)

fixef(a = c(, 0.0005, ))

fixef(Cl0 = c(, 4.3, ))

fixef(tvV = c(, 0.5, ))

fixef(tvV2 = c(, 1.7, ))

fixef(tvV3 = c(, 1.7, ))

~~fixef(tvCl = c(, 4.3, ))~~ ## what if we remove this?

fixef(tvCl2 = c(, 6.5, ))

fixef(tvCl3 = c(, 2.2, ))

secondary(Min_Cl=Cl0 - a * 1000)

}