Data Visualization with D3.js Cookbook

Building a pie chart

A pie chart or a circle graph is a circular graph containing multiple sectors used to illustrate numerical proportion. We will explore techniques, involving D3 pie layout, to build a fully functional pie chart in this recipe. In Chapter 7, Getting into Shape, it becomes clear that using the D3 arc generator directly is a very tedious job. Each arc generator expects the following data format:

var data = [
  {startAngle: 0, endAngle: 0.6283185307179586}, 
  {startAngle: 0.6283185307179586, endAngle: 1.2566370614359172},
  ...
  {startAngle: 5.654866776461628, endAngle: 6.283185307179586}
];

This essentially requires the calculation of the angle partition for each slice out of an entire circle of 2 * Math.PI. Obviously this process can ...