D3 Examples - Polar Area Diagram

Polar Area Diagram
A polar area diagram of world religions with a color legend. This is similar to a pie chart, but with constant angles, varying area proportional to data. This is example 29 from the screencast Splitting Charts.
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<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title>D3 Example</title>
    <script src="//cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
    <script src="//cdnjs.cloudflare.com/ajax/libs/d3-legend/1.1.0/d3-legend.js"></script>
    <link href='https://fonts.googleapis.com/css?family=Open+Sans' rel='stylesheet' type='text/css'>
    <style>
        
      .axis text {
        font-family: 'Open Sans', sans-serif;
        font-size: 32pt;
      }
​
      .axis path, .axis line {
        fill: none;
        stroke: #000;
        shape-rendering: crispEdges;
      }
​
      .color-legend text {
        font-family: 'Open Sans', sans-serif;
        font-size: 29pt;
      }
​
    </style>
  </head>
  <body>
    <script>
​
      var outerWidth = 960;
      var outerHeight = 500;
      var margin = { left: 11, top: 75, right: 377, bottom: 88 };
      var radiusMax = 231;
​
      var xColumn = "name";
​
      var colorColumn = "religion";
      var radiusColumn = "population";
​
      var innerWidth  = outerWidth  - margin.left - margin.right;
      var innerHeight = outerHeight - margin.top  - margin.bottom;
​
      var svg = d3.select("body").append("svg")
        .attr("width",  outerWidth)
        .attr("height", outerHeight);
      var g = svg.append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
      var xAxisG = g.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + innerHeight + ")");
      var pieG = g.append("g");
​
      var colorLegendG = g.append("g")
        .attr("class", "color-legend")
        .attr("transform", "translate(595, -36)");
​
      var xScale = d3.scale.ordinal().rangePoints([0, innerWidth]);
      var radiusScale = d3.scale.sqrt().range([0, radiusMax]);
      var colorScale = d3.scale.category10();
​
      var xAxis = d3.svg.axis().scale(xScale).orient("bottom")
        .outerTickSize(0);
​
      var pie = d3.layout.pie();
      var arc = d3.svg.arc();
​
      var colorLegend = d3.legend.color()
        .scale(colorScale)
        .shapePadding(3)
        .shapeWidth(40)
        .shapeHeight(40)
        .labelOffset(4);
​
      function render(data){
​
        xScale.domain(data.map( function (d){ return d[xColumn]; }));
        radiusScale.domain([0, d3.max(data, function (d){ return d[radiusColumn]; })]);
        colorScale.domain(data.map(function (d){ return d[colorColumn]; }));
​
        pie.value(function (){ return 1; });
        arc.outerRadius(function(d) { 
          return radiusScale(d.data[radiusColumn]);
        });
​
        var pieData = pie(data);
​
        pieG.attr("transform", "translate(" + innerWidth / 2 + "," + innerHeight / 2 + ")");
​
        var slices = pieG.selectAll("path").data(pieData);
        slices.enter().append("path");
        slices
          .attr("d", arc)
          .attr("fill", function (d){ return colorScale(d.data[colorColumn]); });
        slices.exit().remove();
​
        xAxisG.call(xAxis);
        colorLegendG.call(colorLegend);
      }
​
      function type(d){
        d.name = "World";
        d.population = +d.population;
        return d;
      }
​
      d3.csv("religionWorldTotals.csv", type, render);
​
    </script>
  </body>
</html>
​
    