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Continuous observation model

Mlxtran observational model syntax

The DEFINITION: block in the [LONGITUDINAL] section is used to define the observational model:

CODE
DEFINITION: 
observationName = {distribution = distributionType, prediction = predictionName, errorModel = errorModel(param)}

(notice that one can use type=continuous instead of distribution = distributionType)

For example, if the observation is a concentration with a combined error model (Concentration = Cc + (a+b*Cc)*e), the observational error model is written as

CODE
DEFINITION: 
Concentration= {distribution = normal, prediction = Cc, errorModel=combined1(a, b)}

When the observational error is defined in the Mlxtran model file, the user must declare the observational model parameters (a and b in the presented example) as inputs.

Rules and best practices

  • The eventual arguments of the error model can not be calculations, only input names.

  • In Monolix, the user sets the error model through the interface.

  • In Monolix, the name of the error models input parameters can not have any name.

    • The name of the input should correspond to the definition of the error model (ex. a for a constant error model, b for a proportional error model, (a,b) for a combined1 error model, …)

    • If there are several continuous outputs, the names of the error models input parameters should be linked to the order of the outputs (1 for the first error model, …)

    • For example, for a single output, a combined error model writes without any number as follows

      CODE
      DEFINITION: 
      Concentration = {distribution = normal, prediction = Cc, errorModel=combined1(a, b)}
    • For example, for two outputs, a combined error model and a constant error model write as follows

      CODE
      DEFINITION: 
      Concentration = {distribution = normal, prediction = Cc, errorModel=combined1(a1, b1)}
      PCA = {distribution = normal, prediction = E, errorModel=constant(a2)}
  • Notice that a parameter can not be shared by two error models. For example, in the previous Concentration/PCA example, we can not replace a2 by a1.

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