3 Bayesian analysis

library(PKPDmisc)
library(data.table)
library(tidyverse)
library(knitr)
library(infuser)

Core differences

  • Need priors on parameters
  • EM algorithms can more robustly handle full block matrices as well as random effects on less well-defined parameters.

3.1 Priors

Priors in nonmem may be defined in two ways:

  1. By distinguishing the thetas/omegas and their priors in $PRIOR
  • NTHETA=number of Thetas to be estimated
  • NETA=number of Etas to be estimated
    • (and to be described by NETAxBETA OMEGA matrix)
  • NTHP=number of thetas which have a prior
  • NETP=number of Omegas with prior

In our case we have 2 Thetas (TVCL, TVV) and 2 omegas (nCl, nV)

$PRIOR NWPRI NTHETA=2 NETA=2, NTHP=2, NETP=2

Or the preferred way of distinguishing in the block definitions

  • $THETA - fixed effects
  • $OMEGA - random effects
  • $SIGMA - residual error
  • $THETAP - theta prior
  • $THETAPV - variance of theta prior
  • $OMEGAP - omega prior
  • $OMEGAPD - degrees of freedom to prior omega matrix

** TODO: fill out explanations of each. **