Overlay area chart
Overlay area charts show areas from each series independent of each other. The areas appear by joining the values for the series. In an overlay area chart, the areas of multiple series overlap, as shown in Figure 8-8. As the example shows, this chart subtype is not suitable for showing multiple series if the data values overlap. Use an overlay area chart if you want to show only one series, for example, only sales for Asia.
Figure 8-8  

Additional Links:

Copyright Actuate Corporation 2012