Pie and Doughnut series can be linked. This is most visible in Excel when you create a doughnut chart with more than one series; if you change the angle of the first slice, all of the series will rotate. This is because doughnut series, by default in Excel, are created in the same group (you can force it to have multiple groups by doing things like creating a line chart, and converting the series one-by-one to doughnut series). If you have multiple pie series in the same group, only one of them is visible. This linking between series is maintained in the api, and is noted on the individual properties. | 