Creating CLDs

 

Causal loop diagrams are different from regular model diagrams because they depict circular connections without any stocks being displayed. This is because, in a CLD, stocks aren't distinguished from other elements; everything is simply represented by its name. To create causal loop diagrams in Stella, use the New CLD command on the File Menu. This will open the The CLD Window. Then use the variable tool to add names and the connector () tool to connect them up.

Creating CLDs in models

It is also possible to create CLDs in regular models using either modules or delay convertors. This can be useful if you want to create something that has more variety than a regular CLD, or that combines some stock and flow information into a CLD (hybrid diagrams).

Creating a CLD with Modules

  1. Open a new model file.

  2. Open the Model Styles panel for the new model by double-clicking on the blank model and then selecting the tab.

  3. Under Diagram Options, select Name Only for module size.
  4. On the diagram, click the Module tool in the Build toolbar, then click the diagram surface to place modules. Rename the modules to text that describes the connections you want to show. Use connectors to link the modules.
  5. (Optional) Choose the polarity for connectors and flows in your CLD, by right-clicking each connector and then selecting the appropriate polarity (+ or -).
  6. Place one or more Loop Labels in the diagram and give them text such as "R" for reinforcing or even "Death Spiral Loop" to emphasize their importance. Using a large font will help emphasize the loop.

Modules are a good way to lay out a CLD, but the default connector width between modules is 2, and you may need to adjust individual arrow widths downward to get the effect you want.

Creating a CLD with Delay Converters

  1. Open a new model file.

  2. Open the Model Styles panel for the new model by double-clicking on the blank model and then selecting the tab.

  3. Under Diagram Options, select Name Only for converter size.
  4. On the diagram, click the Converter tool in the Build toolbar, then click the diagram surface to place the converter. Rename the converter to text that describes the connections you want to show. Use connectors to link the converters.
  5. When you can't connect a link because of a circularity, determine which converter in the loop that you're trying to connect is like a stock. Right-click on it and select Change to Type, then pick Delay Converter in the menu that appears.
  6. (Optional) Choose the polarity for connectors and flows in your CLD, by right-clicking each connector and then selecting the appropriate polarity (+ or -).
  7. Place one or more Loop Labels in the diagram and give them text such as "R" for reinforcing or "Death Spiral Loop" to emphasize their importance. Using a large font will help emphasize the loop.

Using delay converters forces you to take the extra step of changing some of the converters to delay converters. That step can help identify links along which there must be a delay, which may make annotating your diagram easier. Connecters will have the default width of 1 when placed.

Using Modules and Converters

You can mix converters and modules in laying out a diagram. You can also leave modules with their shape and use these to denote the stock-like entries in the causal loop diagram. For example:

Otherwise, the methodology is the same.

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