Generalized Model Object (GMO)

Generalized model object (GMO) is an RxODE2 model that encodes the full pharmacometric model in simulation syntax: structural parameters, covariate effects, inter-individual variability, and residual error components.

Format

GMO

An RxODE2 model object (rxode2 class). Typical contents:

Typical values

Fixed effects on the log scale (ka_pop, Vd_pop, CL_pop, …) with transformation lines such as ka_tv = exp(ka_pop).

Random effects

Initial values for ETAs (omega_ka, omega_Vd, omega_CL, …) and individual parameters such as ka = ka_tv * exp(omega_ka).

Covariate effects

Covariate coefficients (e.g. beta_Vd_WT) applied to typical values, e.g. Vd = Vd_tv * exp(omega_Vd) * exp(beta_Vd_WT * WT).

Structural model

Initial conditions and ODE equations (Ad, Ac, Cc, …).

Residual error

Error model parameters (e.g. Cc_b) and observation outputs such as Cc_ResErr = Cc * (1 + Cc_b).

Details

Build a GMO with rxode2::rxode2() or use the bundled gmo_pk1c example.

See also

GCO, GSI, gmo_pk1c, sg_sim()

Examples

# \donttest{
class(gmo_pk1c)
#> [1] "rxode2"
gmo_pk1c$model
#> ── rxode2 Model Syntax ──
#> rxode2({
#>     ka_pop = -0.0318013448616758
#>     Vd_pop = 1.03598837793817
#>     CL_pop = 0.24965304895424
#>     omega_ka = 0.127501
#>     omega_Vd = 0.108315
#>     omega_CL = 0.376105
#>     beta_Vd_WT = 0.0210163
#>     Cc_b = 0.184722
#>     ka_tv = exp(ka_pop)
#>     Vd_tv = exp(Vd_pop)
#>     CL_tv = exp(CL_pop)
#>     ka = ka_tv * exp(omega_ka)
#>     Vd = Vd_tv * exp(omega_Vd) * exp(beta_Vd_WT * WT)
#>     CL = CL_tv * exp(omega_CL)
#>     Cc = Ac/Vd
#>     Ad(0) = 0
#>     Ac(0) = 0
#>     d/dt(Ad) = -ka * Ad
#>     d/dt(Ac) = ka * Ad - CL * Cc
#>     Cc_ResErr = Cc * (1 + Cc_b)
#> }) 
gmo_pk1c$params
#> [1] "ka_pop"     "Vd_pop"     "CL_pop"     "omega_ka"   "omega_Vd"  
#> [6] "omega_CL"   "beta_Vd_WT" "Cc_b"       "WT"        
# }