mix: Specify a mixture model of variables

In rxode2: Facilities for Simulating from ODE-Based Models

Specify a mixture model of variables

Description

Specify a mixture model of variables

Usage

mix(...)

Arguments

...

Arguments to the mixture model. The first call to the mixture model function takes an odd number of arguments (at least 3). For example the model we could have: cl = mix(cl1, p1, cl2, p2, cl3) Here there is a mixture of three clearance variables, cl1, cl2, and cl3, at a probability of p1, p2, and the last one is assumed to be 1 - p1 - p2. For simulations this is selected randomly. For estimations this is selected by the data for each individual. After the first call when the number of populations has been established, you can also call the mixture model with the number of populations, for example: v = mix(v1, v2, v3) The ui function will translate this to the following model: v = mix(v1, p1, v2, p2, v3) This is because the first call to mix() sets the probabilities. In rxode2/nlmixr2 these probabilities should be conserved between the models. These probabilities also have to be defined in the ini block directly.

Value

The mixture model replacement for the underlying rxode2 model.

Author(s)

Matthew L. Fidler

Examples

# This is an example of a mixture model
# Where there are 2 different clearance populations

one.cmt <- function() {
  ini({
    tka <- 0.45 # Log Ka
    tcl1 <- log(c(0, 2.7, 100)) # Log Cl
    tcl2 <- log(c(0, 0.1, 120)) # Log Cl
    tv <- 3.45; label("log V")
    p1 <- 0.3
    eta.ka ~ 0.6
    eta.cl ~ 0.3
    eta.v ~ 0.1
    add.sd <- 0.7
  })
  model({
    ka <- exp(tka + eta.ka)
    # This is the example mixture model
    cl <- mix(exp(tcl1 + eta.cl), p1, exp(tcl2 + eta.cl))
    v <- exp(tv + eta.v)
    me <- mixest # This is the assigned mixture estimate
    mn <- mixnum # This is the number of mixture estimate in the model
    # This is the uniform mixture estimate used in simualtion to
    # determine the population
    mu <- mixunif
    linCmt() ~ add(add.sd)
  })
}



s <- rxSolve(one.cmt, et(amt=320, ii=12, addl=2, cmt=1) |>
                      et(seq(0, 72)) |>
                      et(id=1:20))

plot(s, ipredSim)

rxode2 documentation built on July 28, 2026, 5:08 p.m.