Use the DevExpress Charts for Xamarin.Forms to represent data as bars, pies, areas, lines, etc. It supports the Xamarin.Forms and allows you to create native iOS and Android applications in C#.
How to: Add DevExpress Charts to your Xamarin.Forms solution
The DevExpress Pie Chart View allows you to visualize your data as a Pie (Circular) chart.
The DevExpress Chart View allows you to visualize your data as a Cartesian (XY) chart.