Dynamic Hexbin

Computing hexbins from a fluctuating sample of 2,000 random points.

<!DOCTYPE html>
<svg width="960" height="500"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://d3js.org/d3-hexbin.v0.2.min.js"></script>
<script>

var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");

var delta = 0.001,
    i = 0, j,
    n = 2000, // Total number of random points.
    k = 20; // Number of points to replace per frame.

var rx = d3.randomNormal(width / 2, 80),
    ry = d3.randomNormal(height / 2, 80),
    points = d3.range(n).map(function() { return [rx(), ry()]; });

var color = d3.scaleSequential(d3.interpolateLab("white", "steelblue"))
    .domain([0, 20]);

var hexbin = d3.hexbin()
    .radius(20)
    .extent([[0, 0], [width, height]]);

var hexagon = svg.selectAll("path")
  .data(hexbin(points))
  .enter().append("path")
    .attr("d", hexbin.hexagon(19.5))
    .attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })
    .attr("fill", function(d) { return color(d.length); });

d3.timer(function(elapsed) {
  rx = d3.randomNormal(width / 2 + 80 * Math.cos(elapsed * delta), 80),
  ry = d3.randomNormal(height / 2 + 80 * Math.sin(elapsed * delta), 80);
  for (j = 0; j < k; ++j, i = (i + 1) % n) points[i][0] = rx(), points[i][1] = ry();

hexagon = hexagon
    .data(hexbin(points), function(d) { return d.x + "," + d.y; });

hexagon.exit().remove();

hexagon = hexagon.enter().append("path")
      .attr("d", hexbin.hexagon(19.5))
      .attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })
    .merge(hexagon)
      .attr("fill", function(d) { return color(d.length); });
});

</script>

https://d3js.org/d3.v4.min.js

https://d3js.org/d3-hexbin.v0.2.min.js