Variable-Radius Nested Donut Chart
amCharts supports nested pie/donut series. By default it would automatically spread the series within the whole pie. But you can also control [outer]
innerRadius of each series to achieve the look you want. Moreover, pie/donut charts don’t have to be fully circular.
Key implementation details
endAngle on the chart and each series to achieve the overall arc shape. Then we set
radius on the series to control the space each of them occupies.