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<html>
<head>
<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/d3@2.10.3/d3.v2.js"></script>
</head>
<body>
<div id="chart"></div>
<script type="text/javascript">
var w = 800, h = 500;
var colors = d3.scale.category20();
var vis = d3.select("#chart").append("svg:svg")
.attr("width", w)
.attr("height", h);
var data = d3.range(20).map(function() { return { x:Math.random()*w, y:Math.random()*h, r:Math.random()*30 } });
vis.selectAll("circle")
.data(data)
.enter().append("svg:circle")
.attr("stroke", "black")
.attr("fill", function(d, i) { return colors(i); })
.attr("cx", function(d, i) { return d.x; })
.attr("cy", function(d, i) { return d.y; })
.attr("r", function(d, i) { return d.r; })
// Here we add an SVG title element the contents of which is effectively rendered in a tooltip
.append("svg:title")
.text(function(d, i) { return "My color is " + colors(i); });
</script>
</body>
</html>
Modified http://mbostock.github.com/d3/d3.js to a secure url
https://mbostock.github.com/d3/d3.js