As for template-replicated elements, scenarios can also be numerous when there are several dimensions in a model. The Scenarios tab in the Draw dialog is displayed when there are dimensions in a model, and this is where you will then select which scenarios you would like on a results graph.
There are two dimensions in the example WiMAX model (Technology and Video On/Off), as shown below:
Figure 1: Technology and Video On/Off scenarios in the example WiMAX model
After selecting the desired elements and graphs from the relevant tabs, you can switch to the Scenarios tab to select which scenarios you want to appear on your results graph. The Scenarios tab is shown even if the scenarios in the model haven’t been run. If you have out-of-date or not-run scenarios, you can select the Include Out-of-Date Scenarios checkbox (unchecked by default), which will allow you to select these scenarios for inclusion in a results graph at such time as they are updated.
The Linear Selection checkbox on the Scenarios tab is checked by default initially, such that the working model and all up-to-date variant combinations are listed as Available in a single flat list.
By default, only up-to-date scenarios will be shown in the Available list.
Figure 2: List of available scenarios
You can choose which scenarios you are interested in and add them to the Selected list, using the button or by clicking, as in the Elements tab. The list is essentially the same as in STEM 7.4 and works well provided that there are only one or two dimensions in a model – if there are more dimensions, the list very quickly becomes long and unmanageable.
Figure 3: With four dimensions in the model, the linear list soon becomes very long
A new dimensional view in STEM 7.5 makes it more straightforward to choose scenarios if there are several dimensions in a model. If you uncheck Linear Selection, a dimensional view is displayed, in which the Working Model is shown first and then each variant is listed by dimension, even for scenarios which have not been run and are out-of-date.
Figure 4: The dimensional view, in which variants are listed by dimension
If you don’t select any variants at all from this list, then the graph you get will show the results for the Working Model only. If you select a variant from one dimension, and add it to the Selected list, then you are selecting everything that goes with it: for example, if you select Base from the Video On/Off dimension and add it to the selected list, then DSL/Base, WiMAX/Base and Dual/Base will be presented in a linear Selected list – you have selected Base sliced through the scenario space (i.e., all implied combinations selected).
Figure 5: Selection of the single variant Base results in selection of all /Base-associated variants
An individual scenario can be removed from the Selected list at any time: e.g., you could select Dual/Base from the Selected list shown above and remove it by double-clicking or pressing the button. The Selected list always presents specific scenario choices in an explicit linear list.
If you select specific elements from separate dimensions (e.g., DSL and WiMAX from the Technology dimension, and Base from the Video On/Off dimension), then only the relevant combinations will be in the Selected list – DSL/Base and WiMAX/Base. The Working Model can also always be added to the Selected list for graphing.
Figure 6: Selection of specific variant combinations
The idea of this dimensional view is that it is a clear and easy way to rapidly select a logical subset of the dimensional space, and will be particularly useful when there are multiple dimensions in a model. In the example below, DSL and Base were selected specifically from the Technology and Video On/Off dimensions, respectively, resulting in automatic selection of all possible slices through Dimensions 1 and 2 (as listed).
Figure 7: Using the dimensional view to select scenarios when there are four dimensions in a model
Note: initially, the Linear Selection option will be checked in the Scenarios tab. However, if you prefer to use the dimensional view (by unchecking Linear Selection), the results program will remember your preference for future use (i.e., your choice of a linear or dimensional view is ‘sticky’ and is retained for future use).
The Working Model is used if no scenarios have been selected or if you select Disregard Selection to preserve your selections. You can also press Clear Selection if you want to quickly clear all the selected scenarios
As for the other tabs in the Draw dialog, the Separate Graphs option is present and is unchecked by default.