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2 Vensim Applications — Sample Models At the Demo Main Menu, the button Exploration of Sample Models presents models in the form of a Vensim Application, or Venapp. Venapps contain a Vensim model, and a directed way of interacting with that model. Venapps help people unfamiliar with modeling interact and learn from existing debugged and refined models. Explore these Venapps by clicking with the mouse on buttons or menu items. Many Venapps have a similar structure, with individual screens for: 1. Main menu 2. Model structure 3. Setup and Run Simulation 4. Display output 5. Model analysis Try running a simulation using all the default values, then move to model analysis and explore the results. Information presented in Section 3 below helps explain some of the various menu items and analysis tools. Next, run another simulation but with modified initial values (to Constants and/or Lookup Tables), and compare the results with the analysis tools. Some models, such as the Urban Game, are presented in a format (gaming mode) that allows you to change values of variables as the game progresses. You can run or "fly" the model from moment to moment, trying to optimize or achieve various goals. Step-by-step introduction to the Venapp "Financial Modeling and Risk" Click with left mouse button on Financial Modeling and Risk Read, then click on the two opening screens Click on Review model structure, click on buttons to see the three parts of the model, then on Exit to main menu button Click on Run a scenario, enter a name for the run (NOT "base"), e.g., run1, and click OK Click on Enter scenario assumptions, read (or change them) then click Record changes and Return or Cancel Changes and Return (if you don't want to keep the changes) Click on Enter policy choices, read (or change them) then click Record changes and Return or Cancel Changes and Return (if you don't want to keep the changes) Click on Run scenario, observe the output graph Click on Select new variable, double click on Accounts receivable in the Variable selection dialog box to see a different graph. Choose and look at other variables. Click on Run analysis tools Click on (Results): Summary for recently run (first loaded) scenario Click on Analysis of scenario Click on (Causal Tracing): Trace underlying causes using trees. The model is positioned at the workbench variable, the last variable you selected in step 9 (see Section 2 for more information on the workbench variable and causal tracing) Double click on any variable in the tree at the top of the screen, see how the tree changes to show the causes of this variable, with a graph of the variable displayed below If you wish, continue clicking on variables in the tree and trace behavior around the model Click on Exit - return to analysis Click on (Causal Tracing): Trace underlying causes using graphs A set of graphs are displayed; the top graph shows the current workbench variable, the bottom graphs show the causes of that variable. If only numbers (and no graph) are displayed in the right column, the workbench variable is a constant; choose another variable using the button Select a new variable to trace) Double click on any variable in one of the bottom graphs. This variable will become the workbench variable and its behavior and the behavior of variables that cause it to change are displayed If you wish, continue clicking on variables in the bottom graphs. In this way, you can trace through the model looking at causes of a variable's behavior Click on Exit - return to analysis Click on Exit to main menu Click on Run sensitivity analysis If you wish, adjust the sliders, then click on Run Monte Carlo sensitivity analysis Click on different buttons to look at the different variables, continue to explore on your own and Have Fun!
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