D3 Examples - Animating Circles (Canvas)

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<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
  font-family: Helvetica, sans-serif;
}
svg {
  position: absolute;
  top: 0;
  left: 0;
  z-index: -1;
}
.filter-btn.active {
  font-weight: bold;
}
</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script src="d3-grid.js"></script>
<script>
​
var width = 960,
    height = 960
    TAU = Math.PI * 2;
​
var grid = d3.layout.grid()
  .size([width, height]);
​
var color = d3.scale.linear()
  .interpolate(d3.interpolateHcl)
  .domain([0, 100])
  .range(["#F66A96", "#3E6E9C"]);
​
var data = d3.range(5000).map(function(d) { 
  return {
    id: d,
    size: 1 + Math.floor(Math.random() * 5),
    r: Math.random() * 50,
    color: Math.floor(Math.random() * 100),
    f: (Math.random() > 0.5 ? -1 : 1) * (Math.random() * 10000 + 1000)
  }; 
});
​
var nodes = grid(data);
​
var scale = window.devicePixelRatio || 1;
var canvas = d3.select("body").append("canvas")
  .attr({
    width: width * scale,
    height: height * scale
  })
  .style({
    width: width + 'px',
    height: height + 'px'
  });
​
var context = canvas.node().getContext('2d');
context.scale(scale, scale);
​
function update(t) {
  var i, d, alpha;
​
  context.clearRect(0, 0, width, height);
​
  for (i = 0; i < nodes.length; ++i) {
    d = nodes[i];
    alpha = TAU / d.f * (t % d.f);
    context.beginPath();
    context.arc(d.x + Math.cos(alpha) * d.r, d.y + Math.sin(alpha) * d.r, d.size, 0, TAU);
    context.fillStyle = color(d.color);
    context.fill();
  }
}
​
d3.timer(update);
​
d3.select(self.frameElement).style("height", height + "px");
​
</script>
    