Editing edges We may convert the production cost into a negative value in two ways; either by defining the value in the “local factor” field in the “Node dialog box” as a negative value, or by allocating a function to the link or the “edge” between the nodes. As an example, we choose the edge-function option. Select the “Production cost” node. Hold down the Shift key and click on the “Revenue” node. This way both nodes should be selected: Then, choose “Open Edge(s)...” from the “Model”-menu, and a dialog box should appear.