Ch. 5, Fig. 6 - D3.js in Action

This is the code for Chapter 5 from D3.js in Action demonstrating how to make a donut chart using d3.layout.pie() and how to transition it using attrTween to calculate the transition arcs.

<html>
<head>
  <title>D3 in Action Chapter 5 - Example 3</title>
  <meta charset="utf-8" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
</head>
<style>
  svg {
    height: 500px;
    width: 500px;
    border: 1px solid gray;
  }
  
</style>
<body>

<div id="viz">
  <svg>
  </svg>
</div>
</body>
  <footer>
    
<script>
    d3.json("tweets.json",function(error,data) {dataViz(data.tweets)});
    
    function dataViz(incData) {
      nestedTweets = d3.nest()
      .key(function (el) {return el.user})
      .entries(incData);

var colorScale = d3.scale.category10([0,1,2,3]);

nestedTweets.forEach(function (el) {
        el.numTweets = el.values.length
        el.numFavorites = d3.sum(el.values, function (d) {return d.favorites.length});
        el.numRetweets = d3.sum(el.values, function (d) {return d.retweets.length});
      })
      
      pieChart = d3.layout.pie().sort(null);
      pieChart.value(function(d) {return d.numTweets});
      newArc = d3.svg.arc();
      newArc.outerRadius(100).innerRadius(20);

d3.select("svg")
      .append("g")
      .attr("transform","translate(250,250)")
      .selectAll("path")
      .data(pieChart(nestedTweets), function(d) {return d.data.key})
      .enter()
      .append("path")
      .attr("d", newArc)
      .style("fill", function(d, i) {return colorScale(i)})
      .style("opacity", .5)
      .style("stroke", "black")
      .style("stroke-width", "2px")
      .each(function(d) { this._current = d; });
      
      function arcTween(a) {
        var i = d3.interpolate(this._current, a);
        this._current = i(0);
      return function(t) {
      return newArc(i(t));
      };
    }
    
    }

</script>
  </footer>

</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js