Changing Chart Views:
After setting up charts you are interested in examining, you can change the views from uni-wheel (single chart) to square chart or to bi-wheel to compare two charts. There is a "Chart View" combo box near the top left of the Chart Viewer window:
You can either <Tab> to highlight the Chart View combo box and use the arrow keys or click on the down arrow to view the options. If you select "Bi-Wheel" from the chart view, two combo boxes will become enabled so you can select which chart should be put on the inside and outside wheel.
Last, the "Draw" button becomes enabled so that the viewer can draw the arrangement. Also, you can click on the button with 2 red arrows between these 2 combo boxes to swap the inside and outside charts.
Another method of changing to a bi-wheel is to press the <Ctrl + B> keys to bring up the bi-wheel dialog:
After you have selected the charts for the inner and outer wheels, the View button will be enabled so that you can click it to view the arrangement. Any two charts can be compared to eachother and swapped in this manner.