Simulation Properties

Description: Simulation Properties are used to share information between agents. Unlike Attributes, which are local to each instance of an agent, Simulation Properties are global values accessible by all agents. They can be numbers (integers or decimal) used as inputs or outputs for a simulation.

Users can create, inspect and edit the names and values of simulation properties using the Simulation Property Editor, shown below.

To create a new Simulation Property, press the New button. A Property Name dialog, shown below, will prompt you to provide a name for the new Simulation Property.

Type in a valid name and click the OK button. A property called Total is added to the Simulation Properties editor.

Should you need to edit the name of a Simulation Property, select it and press the Edit button and give it a different name.
You can edit the value of a Simulation Property by editing its Property Value field. You can also use the Up and Down arrows to increase or decrease the value of the selected Simulation Property.

Agents can read and write Simulation Properties. For example, in the Virus Attack project, two Simulation Properties are defined, as shown in the editor below:

  • Total: a counter for keeping track of the total number of sick people. Every time a Person agent gets sick, it writes the "Total" Simulation Property using the Set action, incrementing it by 1, as shown in the first rule below.
  • Infection_Percentage: the percentage a healthy Person has of acquiring the virus. %Chance reads the Simulation Property and uses its value, as shown in the first rule below:

The "@" sign is used to differentiate Simulation Properties from agent Attributes. Please note that you should not add the "@" sign when you are creating the property in the Simulation Properties editor, but you must use it when you refer to a property in a VAT Formula.

You can plot a Simulation Property, by select it and pressing the Plot button. A window like the one shown below will appear prompting you to select the plotting settings.

We want to plot the "Total" property. We check the plot check box and we specify the following:

  • the name of the window we want to plot in (in this case, "Sick Population")
  • what the property represents (in this case the "Total Number of Sick People")
  • the range of the plotted values, that is, the minimun and maximun numbers to be represented in the plot (in this case, 0 to 80)
  • the color of your plot

After deciding on the plotting settings, click OK. When the simulation runs, a plot window (shown below) will appear, if one does not already exist with the same name.

Please note that you can plot multiple values in a single window. For the Predators & Prey simulation, both the number of large and small fish is plotted in the same Population window (shown below). That way you can see the relationship between and the fluctuations of the two populations.

When a plot window is control-clicked (or right-clicked with a mouse with multiple buttons), the cursor changes from the regular to and the following options are available through the following contextual menu:

Set Min/Max Value... enables you to change the plotting range, that is the minimum and the maximum number to be represented in the plot. The following window appears.

Selecting Goto Time... enables you to jump to a particular time value in your plot. The following window appears.

Selecting Export to Excel... allows you to export the data from the current plot window that can contain any number of values being plotted to an Excel spreadsheet. The Save as Microsoft Excel Workbook file dialog appears for you to specify the name and location of the exported spreadsheet.

Reset clears the plot in the current plot window.

Plot Control: Scrolling in available on a plot so that you can scroll back and forth through time.

To scroll to the right, click on the plot window and drag to the right. The cursor changes to to indicate that you are scrolling to the right. When the end of the plot is reached, the cursor changes to .

To scroll to the left, click on the plot window and drag to the left. The cursor changes to to indicate that you are scrolling to the left. When the end of the plot is reached, the cursor changes to .

Plotting can also be done within an agent's behavior using the Plot to Window action.

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