An example of multiple pie (donut) charts created with D3. The data is represented as a tabular array of objects; each row in the table is mapped to an arc, and rows are grouped into pie charts using d3.nest.
d3.nest
http://stackoverflow.com/questions/18668271/apply-d3-nest-rollup-to-nested-pie-chart-to-vary-the-size-of-the-pies