# The Chained Slider

The Chained Slider builds on the basic functions and principles of operation found in the Slider object. It is useful when you have interdependent decisions - i.e., you want to permit the user to manipulate the values of each decision variable, but restrict the combined total value of the variables. For example, allocating a fixed capital budget among three major spending categories would be a good use for a Chained Slider.

The Chained Slider limits the assigned variables to a total maximum value of 100, distributed between the variables that are assigned to it. The distribution between variables is generated by the current slider settings, as determined by the model user. Frequently you will use the generated numbers as percentages applied to a resource in your model. For instance, if you want to allocate company spending between Human Resources and Research & Development, apply the Chained Slider values (number between 0 and 100) to the Total Amount available - this will calculate the real dollar amount for each of the two departments. Figure 6-36 demonstrates this concept using a sample diagram and the corresponding Chained Slider.

Figure 6-36 Chained Slider with Diagram Structure

Note: Since a Pause in the simulation will occur following a full round of calculations (i.e., all Converters and Flows will be calculated then the Stocks updated), it is advisable to use a Stock as the Available Resource. Then the user can view the value of the Stock on a table or numeric display during a pause to determine the adjustment to the Chained Slider. If placed in a Converter or Flow, the Available Resource value will be updated at the same time as the slider value (after the simulation is resumed).

Basic Operations. After depositing an unassigned Slider on the Interface level, double-click on the icon to access the Slider dialog. Then, check the Chaining check box. The dialog will be transformed into something that looks like Figure 6-37, below.

Figure 6-37 Chained Slider Dialog Box

Once you have loaded variables to the selected list, check the display check boxes to achieve the desired effect on the slider surface. When you're all set, click OK to exit the dialog. Figure 6-38 illustrates an assigned Chained Slider.

Figure 6-38 Chained Slider with Unallocated Portion

In the lower right corner of the Chained Slider casing, you will see two values marked "Allocated" and "Unallocated." These two values will always sum to 100. Allocated will always equal the sum of the numerical values of the component Sliders. Think of these as doing "scorekeeping" for the Chained Slider total.

To restore the elements of a Chained Slider to their original values, click on the "U" button of the bottom left of the Sliders. These "U" buttons appear whenever the Slider's button has been moved. Alternately, choose Restore then Sliders from the Map or Model menu.

Increasing the magnitude of one element of the chain: When the user of your model drags the slider button to the right, increasing the magnitude of its associated variable, the slider will ensure that no more than 100% in total is allocated. If necessary, other elements in the chain will be reduced proportionately.

Decreasing the magnitude of one element in the chain: As the user drags the slider button to the left, decreasing the magnitude of its associated variable, the other elements of the chain will remain unchanged. The "unused" portion of the Chained Slider's total will be displayed as Unallocated in the lower right corner of the Slider housing. Under this scenario, a user might choose to increase the allocation to other variables until the unallocated portion = 0. Alternatively, the user could choose to leave a portion unallocated.