SVG chart generation in JavaScript

Question

I'm looking for a way to generate pie charts using SVG.

The numbers I have are simple enough - just percentages, an array of numbers that obviously add up to 100.

I have a basic understanding of SVG, but I can't think how to translate these numbers into meaningful coordinates to use in the path tag

Can anyone point me to a useful utility or library, or give any hints as to how I could use percentages to draw a pie chart - in JavaScript?

Answer 1

Credits to https://stackoverflow.com/a/3642265/309483 and http://jbkflex.wordpress.com/2011/07/28/creating-a-svg-pie-chart-html5/ (note that the last one has a bug, fixed here)

function makeSVG(tag, attrs) {
    var el= document.createElementNS('http://www.w3.org/2000/svg', tag);
    for (var k in attrs)
        if (attrs.hasOwnProperty(k)) el.setAttribute(k, attrs[k]);
    return el;
}

function drawArcs(paper, pieData){
    var total = pieData.reduce(function (accu, that) { return that + accu; }, 0);
    var sectorAngleArr = pieData.map(function (v) { return 360 * v / total; });

    var startAngle = 0;
    var endAngle = 0;
    for (var i=0; i<sectorAngleArr.length; i++){
        startAngle = endAngle;
        endAngle = startAngle + sectorAngleArr[i];

        var x1,x2,y1,y2 ;

        x1 = parseInt(Math.round(200 + 195*Math.cos(Math.PI*startAngle/180)));
        y1 = parseInt(Math.round(200 + 195*Math.sin(Math.PI*startAngle/180)));

        x2 = parseInt(Math.round(200 + 195*Math.cos(Math.PI*endAngle/180)));
        y2 = parseInt(Math.round(200 + 195*Math.sin(Math.PI*endAngle/180)));

        var d = "M200,200  L" + x1 + "," + y1 + "  A195,195 0 " + 
                ((endAngle-startAngle > 180) ? 1 : 0) + ",1 " + x2 + "," + y2 + " z";
        //alert(d); // enable to see coords as they are displayed
        var c = parseInt(i / sectorAngleArr.length * 360);
        var arc = makeSVG("path", {d: d, fill: "hsl(" + c + ", 66%, 50%)"});
        paper.appendChild(arc);
        arc.onclick = (function (originalData) { 
          return function(event) {
            alert("Associated pie piece data: " + originalData);
          }
        })(pieData[i]);
    }
}
var svgdoc = document.getElementById("s");
drawArcs(svgdoc, [52,15,20,80]); // here is the pie chart data

// You can attach additional content (from e.g. AJAX) like this:
var parser = new DOMParser();
var docToEmbed = parser.parseFromString(
  "<svg xmlns='http://www.w3.org/2000/svg'><text x='50' y='50' fill='black'>hi</text></svg>", 
  "image/svg+xml");
Array.prototype.slice.call(docToEmbed.documentElement.childNodes).forEach(function(elem) {
  svgdoc.appendChild(document.importNode(elem, true));
});

#con {
  resize:both;
  overflow:hidden;
  display:inline-block;
  width:20em;
  height:20em;
  padding:0.5em;
}

<div id="con">
<!-- the div container is of course optional. It is used with 
     {width,height}="100%" below to make the chart resizable. -->
<svg width="100%" height="100%" id="s"
 xmlns="http://www.w3.org/2000/svg" viewbox="0 0 400 400">
  <style type="text/css">
    path:hover {
      opacity: 0.8;
    }
  </style>
</svg>
</div>

Answer 2

Here are a few more:

• Elycharts (based on jQuery and Raphaël, MIT license)
• ZingCharts (commercial, has SVG/VML/HTML5/Flash backends)
• Grafico (based on Prototype and Raphaël, MIT license)
• d3.js (very nice library for interactive and dynamic graphs, MIT-like license)

I try to collect links to all svg graphing libraries here.