Creating scenarios
Scenarios let you set up different... scenarios. This is useful when comparing different discrete options. For example, you might be trying to decide whether to hire 5 people or 10 people this year.
A scenario is a variant of your model in which some variables have different values or formulas. The structure of the model — the variables, groups, and sections — doesn't change across scenarios.
You can visualise multiple scenarios together in charts and tables, to easily compare them. See Comparing scenarios in charts/tables.
You can't perform calculations across scenarios. For example, you can't sum the values of a variable under different scenarios.
A scenario is a live variant of your model in which some variables have different values or formulas.
- The structure of the model — the variables, groups, and sections — doesn't change across scenarios.
- If you change the formula/value of a variable, it will no longer be linked to the default scenario.
- If you don't change the formula/value of a variable, then it will still be linked to the default scenario.
Let's consider an example to illustrate how scenarios work:
- 1.You have a variable, Growth Rate, with a value of 10% in the default scenario.
- 2.You create a new scenario, S1.
- 3.In the default scenario, you change Growth Rate to 15%. This change will be applied to both the default scenario and S1, so Growth Rate will be 15% in both scenarios.
- 4.Next, you navigate to scenario S1 and change Growth Rate to 20%. This action "unlinks" Growth Rate in S1 from the default scenario. The variable will be highlighted in blue within the scenario to indicate this dissociation.
- 5.Now, you return to the default scenario and change Growth Rate back to 10%. Since the variable is unlinked from the default scenario, this modification will not affect Growth Rate in S1 anymore.
There are two ways to create a scenario:
- 1.Right-click on a variable and click New Scenario
- 2.Click on Scenarios in the toolbar, and then click Add new scenario.
Note: if you have a set of linked models - the Scenario will automatically apply across all models. If you subsequently create a new linked model and want your scenarios to be pulled across, see the section here for more info.
To activate a scenario, click on Scenarios in the toolbar, and select the scenario. This will take you into Scenario mode. In this mode, you'll be able to change the value of any variable, and this change will only be applied in the active scenario.
Variables that have been changed in a scenario will have a light blue background.
You also have the following actions by clicking the Scenarios button (as per screenshot below):
- Rename the scenario by double-clicking the name
- Inspect the scenario by hitting❓
- Clone the scenario
- Delete the scenario
- Override the default scenario with the selected scenario
- If other scenarios exist after overriding the default model with another, all unchanged values for variables in the other scenarios will all revert to the values of the new, default model.
- In other words, if you have a base model and two additional scenarios: Scenario A and Scenario B, and the base model is overridden by Scenario A to be the default model, then all of the variables in Scenario B that were unchanged from the original, default scenario, those variables will now take on the values of the new, default scenario)
If you subsequently link a (new or existing) model, to a model(s) that already has a saved scenario, you might notice that your saved scenarios are missing in the newly linked model. To add those previously saved scenarios, create a new scenario in the newly linked model with the exact name as the scenario(s) you want to retrieve (including spelling, capitalization, spacing, etc). Your model may need to be refreshed before your scenarios get loaded properly.