Donut Chart
Donut Chart (also known as Doughnut chart) is a variation on a Pie chart except it has a round hole in the center which makes it look like a donut, hence the name. This empty space can be used to display additional data.
Configurable inner radius
To make a donut chart out of a regular pie chart, we simply need to set innerRadius setting of the chart.
It can either take relative percent value, or fixed pixel radius.
Related tutorials
Demo source