# The Slider Input Device

The Slider Input Device allows model users to adjust constant values, and to override equation logic (and graphical function relationships) with numerical inputs.

Important to note:

- You are allowed only one Slider per variable; if you've assigned a variable to a Slider, it won't be available to assign to another Slider.

- If a Slider is associated with a graphical function, that graphical function will not be available for association with a Graphical Input Device (and vice versa).

- Sliders cannot be associated with: Reservoirs, Conveyors, Queues, Ovens, Conveyor outflows, Queue outflows, Oven outflows, Sub-model icons, Sub-model roll-up Flows, and roll-down Flows within Sub-models.

Basic Operations: Click once to select the Slider from the Interface Layer Tool Bar. Click once to deposit it. An unassigned Slider looks like the one shown in Figure 6-32.

Figure 6-32 Hand Operations on Unassigned Slider

Open the Slider either by double-clicking within its border, or by selecting it and choosing Open Selection... from the Interface menu. You will see the Slider's Define dialog, shown in Figure 6-33.

To move a variable from the Allowable list to the Selected box, either double-click it, or select it and click the >> button. This will automatically replace a previously selected variable.

If you check the "Reset to:" box, another box will appear within which you can provide a numeric value to which the Slider will re-set either "After one time unit" or "After one DT" depending on your radio button selection. These features enable the modeler to save end-users from repeating themselves, by preventing them from inadvertently buying 10 houses, or hiring 10 people a month for 2 years, when they really only wanted to execute each of these actions once.

Figure 6-33 Slider Define Dialog

When you click OK within the dialog, you'll see something similar to what's shown in Figure 6-34.

Figure 6-34 Assigned Slider

As shown in Figure 6-35, sliders associated with model constants (i.e., as opposed to variables that were defined using an algebraic equation or as a graphical function), will display a Restore button in the lower left corner of the Slider housing. The Restore button will appear whenever the Slider's knob is moved. Clicking the button will cause the Slider's value to be restored to the numerical value that appears in the variable's equation box.

Figure 6-35 Slider Assigned to Constant

Helpful Hint: The Restore: Sliders menu item under the Map/Model or Interface menu will reset all sliders with constant values to their original values.

It is possible for the value set for a slider to be overridden by the constraints of Stocks. Under the following conditions, what you set won't be what you get:

- Slider assigned to outflow from a non-negativity restricted reservoir, when the non-negativity constraint comes into play.

- Slider assigned to inflow of capacity constrained or inflow limited Conveyor, when the constraint/limit would otherwise be exceeded.

- Slider assigned to inflow of Oven, when it is cooking.

- Slider assigned to inflow of Oven/Conveyor, when it is arrested.

See Chapter 14 for a discussion of the "rules of grammar" associated with stocks and flows.