Creating a pie diagram is as easy as providing a number of chart-column elements. You can configure a few options using the chart-pie directive.

<c3chart bindto-id="pie-plot1-chart" sort-data="desc">
    <chart-column column-id="Data 1"
                  column-values="70"
                  column-type="pie"/>
    <chart-column column-id="Data 2"
                  column-values="35"
                  column-type="pie"/>
    <chart-column column-id="Data 3"
                  column-values="60"
                  column-type="pie"/>
    <chart-pie expand="true" show-label="true" threshold-label="0.1"/>
</c3chart>