Vensim makes it very easy to get a graph of any variable. Just simulate the model, select the variable you want to graph, then click on the Graph tool or Strip Graph tool on the right.
You can select variables by double clicking on them in the model structure or tool output or by using the Variable tab of the control panel. When you select a variable in this manner it appears in the title bar and is called the workbench variable. The tools on the left operate on the workbench variable. Click on the tool you want to use and a graph or table for the workbench variable will appear.
The toolbar is shown here. The tools, from top to bottom are:
Causes Tree shows a tree made up from the variable, the other variables in the model that cause that variable and the variables in turn that cause those variables. Angle brackets <> are used to indicate that a variable has already appear in the diagram.
Uses Tree shows a tree made up from the variable, the other variables in the model that use that variable and the variables in turn that use those variables. Angle brackets <> are used to indicate that a variable has already appear in the diagram.
Loops lists the feedback loops in the model involving the workbench variable.
Doc documents the workbench variable. It will show its equation, units of measure and definition.
Causes Strip shows a graph of the Workbench variable and the causes of the Workbench variable. If more than one run is loaded a line is drawn for each loaded run. Each of the causes (and each subscript element if multiple subscripts are loaded) is given a separate graph but all appear in a single window if space permits.
Graph shows a graph of the workbench variable with a different line for each loaded run (and each subscript element if multiple subscripts are selected).
Table show the value for the Workbench variable at each time in a table. Same content as the graph tool with a different presentation.
Table Time Down shows the same thing as Table except Time will be running down instead of across. This is useful for longer simulation runs.
Runs Compare displays the changes that have been made in one run relative to another. The first and second loaded runs both need to come from simulation. A list of Constants and Lookups that have changed in value is displayed.
Causal Tracing®
Causal Tracing is a patented process for digging into the causes of behavior. To perform it create a Causes Strip of a variable of interest. Now double click on the cause that seems most important and click again on the Causes Strip tool. You will now see a graph of the variable you selected and its causes. Again double click on the variable you consider most important and repeat the process. This is called Causal Tracing.
