Parameter

Parameters are objects that hold values and that are used in other objects of the model, for instance in Transfers and Expressions. The value of a parameter must remain constant through a simulation, and is given either as a number or a probability density function.

For time dependent data, use a Lookup table.

Creating a parameter

From the Projects window

  • Expand the Project to which you wish to add the compartment by clicking the + symbol next to it. Right-click on ‘Blocks’, or a sub-system in ‘Blocks’, and select Parameter from the pop-up menu.

From the Model window

  • Right click an empty diagonal cell of the matrix and select Parameter from the the pop-up menu.

From the Blocks window

  • Place the mouse cursor over the table and right-click on it. Select New | Parameter from the pop-up menu, or

  • In the title bar, select Parameter from the Type drop-down list and click on the New button.

Editing a parameter

The block editor is shown by right-clicking the block in a window and selecting Edit. In the Blocks window, you can also show the block editor by selecting the block and clicking the Edit button, or by double-clicking the right-most “validation” column of the block.

The block editor has three tabs:

Properties

This page lets you edit basic properties such as name, sub-system and base unit. See editing properties for more information.

Matrix

This page lets you edit the visual properties of the block in the Model window. See Editing matrix properties for more information.

Values

Here you edit index specific values such as nominal values and probability density functions. You can assign both a value and a probability distribution to a parameter. In order for the PDF to be used during the simulation, you must select the parameter in the probabilistic settings window.

More about the PDFs available in Ecolego may be found in probability density functions.

Dimension - You can specify the dimension of the parameter by using the Type drop down list. Depending on the dimension the index drop down lists are activated.

Data - The data table contains the following columns:

  • Indices - For parameters that are non-scalar, the first columns will specify indices from the Index lists. This allows you to specify different values for different indices. The top row is named “default” and can be used when the same value should be set for all indices.

  • Value - This is where the nominal (deterministic) value of the parameter is defined.

  • Min - The minimum value. Is used by some sentitivity analysis methods.

  • Max - The maximum value. Is used by some sentitivity analysis methods.

  • PDF - The probability density functions are easiest defined by using the PDF editing tool which is activated once you click a field in the PDF column.

  • Unit - The unit serves only as a comment.

  • Information - By using the Table control button you can display more columns that will help you document your model.

Database

The database tab lets you quickly import values for the edited parameter from either the local or external database. Please refer to Quick parameter import.

Note Most block properties can be edited directly in the Blocks window.

See also