The Formula Bar allows you to easily write short R expressions, called formulas, to be used in calculations. Formulas can be used to define how inputs to your model should be used in calculations of transition probabilities, costs, and outcomes. The Formula Bar appears in various places throughout the application, and can be activated by double-clicking on any formula cell or hitting the Tab Key.

Once the Formula Bar is open, you can enter a constant value, or you can perform a calculation by typing in an R-expression. As you type in a formula, suggestions of functions or variables you may want to use are provided in a box appearing below the Formula Bar. You can navigate to a particular suggestion using the arrow keys, and then either click on it or hit the Tab Key to accept it. Documentation on suggested functions can be accessed simply by clicking the Help button in the corresponding row. If your formula includes a variable that you have defined previously in your model, it will be shown as a colored pill, where the color corresponds to the type of variable it is (eg, hēRo3 keywords are purple, health values are green, etc.).

Once you are done editing a formula, you can accept it by hitting the Enter Key or by clicking the check mark on the right-hand side of the Formula Bar. Changes can be cancelled by hitting Esc, or by clicking the symbol, 'X'.