Pie charts

The Pie graph can be used as follows:

var Pie = require('paths/pie');
var pie = Pie({
  data: [
    { name: 'Italy', population: 59859996 },
    { name: 'Mexico', population: 118395054 },
    { name: 'France', population: 65806000 },
    { name: 'Argentina', population: 40117096 },
    { name: 'Japan', population: 127290000 }
  ],
  accessor: function(x) { return x.population; },
  compute: {
    color: function(i) { return somePalette[i]; }
  },
  center: [20, 15],
  r: 30,
  R: 50
});

Parameters:

• center, r, R: have the same geometric meaning as in the Sector function
• data: contains an array with the data to plot. The precise form of the data is not important, because the actual value of the data will be extracted by the accessor function.
• accessor: a function that is applied to each datum in data to extract a numeric value
• compute (optional): see the introduction.

The object returned by the Pie function contains the curves array, on which one can iterate to draw the sectors. Each member of this array has the properties sector, index and item, the latter containing the actual datum associated to the sector.