Model Parameter Propagation/Conversion during Model Switching

The behavior of PKIN when switching between models is governed by the Model conversion check in the Extras pane, and the corresponding Conv option in the taskbar.

Model Conversion Disabled

The first time a model is selected for a particular region, the model default values are used. Thereafter, the most recent model parameter set as used for the same region is applied.

Model Conversion Enabled

Model conversion can be used to propagate parameter values from one model to another which includes the same parameter, or to convert compartment parameter values due to a change of model complexity.

• Parameter propagation: Parameter propagation allows to transfer the exact value of certain parameters from one model to another. This feature can for instance be used to fit a parameter using a robust method and propagate it to a more complex model where it is fixed during fitting. Examples of important propagated parameters are vB, t*, Flux, k₂'.
• Parameter conversion: When switching between models with the same number of compartments, the conversion is exact. If the number of compartments is decreased, the lumped parameters of the simplified model are calculated. If the number of compartments is increased, the same values are used for corresponding parameters, and the additional parameters set to the default values. The consequence of this functionality is that when switching the model from 1-tissue to 2-tissue and then back, the K₁ and k₂ values will be different due to this conversion process.