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Simple D3 Pie Chart with Magnitudes in Arcs and Legends Outside and Along Arcs
<!DOCTYPE html>
<meta http-equiv="Content-type" content="text/html; charset=utf-8">
<title>Testing Pie Chart</title>
<script type="text/javascript" src=""></script>
<!-- Source for example located at: -->
<style type="text/css">
.slice text {
font-size: 16pt;
font-family: Arial;
<script type="text/javascript">
var canvasWidth = 300, //width
canvasHeight = 300, //height
outerRadius = 100, //radius
color = d3.scale.category20(); //builtin range of colors
var dataSet = [
{"legendLabel":"One", "magnitude":20},
{"legendLabel":"Two", "magnitude":40},
{"legendLabel":"Three", "magnitude":50},
{"legendLabel":"Four", "magnitude":16},
{"legendLabel":"Five", "magnitude":50},
{"legendLabel":"Six", "magnitude":8},
{"legendLabel":"Seven", "magnitude":30}];
var vis ="body")
.append("svg:svg") //create the SVG element inside the <body>
.data([dataSet]) //associate our data with the document
.attr("width", canvasWidth) //set the width of the canvas
.attr("height", canvasHeight) //set the height of the canvas
.append("svg:g") //make a group to hold our pie chart
.attr("transform", "translate(" + 1.5*outerRadius + "," + 1.5*outerRadius + ")") // relocate center of pie to 'outerRadius,outerRadius'
// This will create <path> elements for us using arc data...
var arc = d3.svg.arc()
var pie = d3.layout.pie() //this will create arc data for us given a list of values
.value(function(d) { return d.magnitude; }) // Binding each value to the pie
.sort( function(d) { return null; } );
// Select all <g> elements with class slice (there aren't any yet)
var arcs = vis.selectAll("g.slice")
// Associate the generated pie data (an array of arcs, each having startAngle,
// endAngle and value properties)
// This will create <g> elements for every "extra" data element that should be associated
// with a selection. The result is creating a <g> for every object in the data array
// Create a group to hold each slice (we will have a <path> and a <text>
// element associated with each slice)
.attr("class", "slice"); //allow us to style things in the slices (like text)
//set the color for each slice to be chosen from the color function defined above
.attr("fill", function(d, i) { return color(i); } )
//this creates the actual SVG path using the associated data (pie) with the arc drawing function
.attr("d", arc);
// Add a legendLabel to each arc slice...
.attr("transform", function(d) { //set the label's origin to the center of the arc
//we have to make sure to set these before calling arc.centroid
d.outerRadius = outerRadius + 50; // Set Outer Coordinate
d.innerRadius = outerRadius + 45; // Set Inner Coordinate
return "translate(" + arc.centroid(d) + ")";
.attr("text-anchor", "middle") //center the text on it's origin
.style("fill", "Purple")
.style("font", "bold 12px Arial")
.text(function(d, i) { return dataSet[i].legendLabel; }); //get the label from our original data array
// Add a magnitude value to the larger arcs, translated to the arc centroid and rotated.
arcs.filter(function(d) { return d.endAngle - d.startAngle > .2; }).append("svg:text")
.attr("dy", ".35em")
.attr("text-anchor", "middle")
//.attr("transform", function(d) { return "translate(" + arc.centroid(d) + ")rotate(" + angle(d) + ")"; })
.attr("transform", function(d) { //set the label's origin to the center of the arc
//we have to make sure to set these before calling arc.centroid
d.outerRadius = outerRadius; // Set Outer Coordinate
d.innerRadius = outerRadius/2; // Set Inner Coordinate
return "translate(" + arc.centroid(d) + ")rotate(" + angle(d) + ")";
.style("fill", "White")
.style("font", "bold 12px Arial")
.text(function(d) { return; });
// Computes the angle of an arc, converting from radians to degrees.
function angle(d) {
var a = (d.startAngle + d.endAngle) * 90 / Math.PI - 90;
return a > 90 ? a - 180 : a;
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