Specifying the Input

Step 1 Box Variables

Recall that our hypothetical school has 100 kids. Set the initial number of susceptible people to 99 and set the number of infected people to 1.

Procedure:

• Click on the Equations button on the toolbar.
• Every object that now appears in black is not sufficiently defined.
• Click on Susceptible People and a window like the one below will pop up. This probably looks complex, but you won't need most of these options at first.
• The cursor should already be in the box to the right of the words Init Value. Here, type in 99.
• Next, click in the box to the right of Units and type people.
• Click OK in the bottom left of the window to finish.


• The procedure for setting the initial number of infected people is analagous, except of course that there is only 1 infected person at time zero.

Input Window

NOTICE: It may seem as though labeling the units is redundant here, but labeling units this way will enable you to use Vensim PLE's Unit Checker, a very useful tool for catching inconsistencies in your model.