Exercise 7: Installed and incremental units; capex and opex results

Watch the video presentation and/or read the full text below

Now we are going to examine the essential results for the Optical interface resource, applying techniques we learned earlier for drawing graphs:

1. Run the model again. (You can just press <F5> in the Editor.) There should no longer be any warnings at this stage, and the Results program is activated directly.
2. Draw the graph Installed Units for the resource Optical interface the same way that we drew the first graph for the service earlier. The numbers should be the same as the Connections result for the service.
3. Use the Draw Similar technique to draw the additional graphs Capital Expenditure and Operating Costs. The latter should match the shape of the Installed Units graph, as an annual maintenance cost of USD 25 will arise from each installed unit, and this is the only opex item we have defined so far. As the installed base approaches 1000, the total annual opex at this stage should approach USD 25 000.
4. Tile the graphs again before proceeding.

Figure 17: Installation and cost results for the Optical interfaceresource

But what about the Capital Expenditure graph? What drives the shape of this graph? We will take this opportunity to learn another useful technique:

5. Right-click the background of the Installed Units graph and select Change Selections… from the context menu. The Draw dialog is displayed again, with the current element and graph selections for this graph.
6. Go straight to the Graphs tab, select Installed and Incremental Units, and press OK. The graph is redrawn showing both results. Evidently, the red line reflects the total, while the blue one indicates how many units are added in a given year; i.e., the ‘delta’. You should see that the Capital Expenditure graph matches the shape of the blue line, and that the magnitude is scaled by the specified USD 500 per unit. It is also easy to verify that the total capex over the ten years amounts to almost USD 500 000.

Figure 18: Using the Change Selections command to alter the current graph

Note: the Change Selections command is very similar to Draw Similar, except that it alters the current graph, rather than cloning it.

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