The Region Baselines command opens a dialog box which allows you to specify what lines are used for baselines on what regions.
In the figure depicted below, there is one region which is currently being drawn to the zero-line. There is also a line which has been drawn, and is the desired baseline for the region.
To select the line (Line 1) as the baseline for the region, select the Region Baselines command. This opens the Region Baseline Settings dialog box which contains a list of all the regions, as well as a list of all the lines on the graph.
Notice that Region 1 is selected in the Region list and None is selected in the Baseline list. To make Line 1 the baseline for Region 1, click on the Line 1 in the Baseline list. If there is more than 1 line, you may select any line as the baseline. If there is more than 1 region, you must select the region for which you wish to set the baseline.
The Update Lists button updates the list of Regions and Baselines, if you have added a baseline or region while this dialog box is open.
When you are satisfied with your selections, click the Close button. The graph is updated to reflect the new baseline for the region as shown below.