Variable parameters

A value of a variable parameter is not stored with the model, but is supplied by the user when the model runs. The value can change during the simulation. There are several ways to set the value of a variable parameter. One is to use slider controls. These can be displayed in the run-time environment and provide a mechanism for the user to observe and adjust the value of the parameter. The other is to use scenario files. These are loaded as the model is built or reset, and can provide a time-series of values for the parameter.

Maximum and minimum values must be set to define the range of acceptable values for the parameter. This allows the slider control to be shown with the correct range. It is also possible to define whether the slider moves continuously or in integer increments. Use the "Units" field to define the units as integer (int) or real to effect this distinction. Finally, it is also possible to present a check-box to the user, to return the Boolean values true or false. This is accomplished by setting the "Units" field to boolean.

Use the equation dialogue box to designate a variable as an variable parameter. It is also possible to set the initial value of a compartment in the same way. A variable parameter is shown on the model diagram with a slider bar behind its usual appearance.

In: Contents >> Working with equations >> Parameters