Hi Sara,
You can also uncheck use closed form, and then edit as textual. This will give you the full PML model code and you can see the derivations of A, alpha, etc.
test(){
deriv(Aa = - Ka * Aa)
deriv(A1 = Ka * Aa - Ke * A1 - K12 * A1 + K21 * A2)
deriv(A2 = K12 * A1 - K21 * A2)
dosepoint(Aa, idosevar = AaDose)
C = A1 / V
error(CEps = 1)
observe(CObs = C + CEps)
stparm(Ka = tvKa * exp(nKa))
stparm(V = tvV * exp(nV))
stparm(Ke = tvKe * exp(nKe))
stparm(K12 = tvK12 * exp(nK12))
stparm(K21 = tvK21 * exp(nK21))
fixef(tvKa = c(, 1, ))
fixef(tvV = c(, 1, ))
fixef(tvKe = c(, 1, ))
fixef(tvK12 = c(, 1, ))
fixef(tvK21 = c(, 1, ))
secondary(Ktot = tvK12+tvK21+tvKe)
secondary(r1 = (Ktot^2-4*tvK21*tvKe)^0.5)
secondary(Alpha = (Ktot+r1)/2)
secondary(Beta = (Ktot-r1)/2)
secondary(Gamma = tvKa)
secondary(a1 = (tvK21-Alpha)/(Beta-Alpha))
secondary(b1 = (tvK21-Beta)/(Alpha-Beta))
secondary(KaAlpha = tvKa/(tvKa-Alpha))
secondary(KaBeta = tvKa/(tvKa-Beta))
secondary(aa = KaAlpha*a1)
secondary(bb = KaBeta*b1)
secondary(cc = -(aa+bb))
secondary(DoseOverVol = AaDose/tvV)
secondary(A = DoseOverVol*aa)
secondary(B = DoseOverVol*bb)
secondary(C = DoseOverVol*cc)
secondary(AUC = DoseOverVol/tvKe)
secondary(Cl = AaDose/AUC)
secondary(Alpha_hl = log(2)/Alpha)
secondary(Beta_hl = log(2)/Beta)
secondary(Tmax = CalcTMax(A,Alpha, B, Beta, C, Gamma))
secondary(Cmax = A*exp(-Alpha*Tmax)+B*exp(-Beta*Tmax)+C*exp(-Gamma*Tmax))
secondary(Ke_hl = log(2)/tvKe)
secondary(Ka_hl = log(2)/tvKa)
secondary(Cl2 = tvK12*tvV)
secondary(V2 = Cl2/tvK21)
ranef(diag(nV, nKa, nKe, nK12, nK21) = c(1, 1, 1, 1, 1))
}