Voronoi tests

Tests for edge cases with d3.geom.voronoi, mainly N=2.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

svg {
  float: left;
  margin: 10px 0 0 10px;
}

path {
  fill-opacity: .2;
  stroke: #000;
}

circle {
  stroke: #fff;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var width = 85,
    height = 85;

var voronoi = d3.geom.voronoi()
    .clipExtent([[.5, .5], [width - .5, height - .5]]);

var color = d3.scale.category10();

var p0 = [20, 20],
    p1 = [width - 20, 20],
    p2 = [20, height - 20],
    p3 = [width - 20, height - 20],
    p4 = [width / 2, height / 2],
    p5 = [width / 2, 20],
    p6 = [width / 2, height - 20],
    p7 = [20, height / 2],
    p8 = [width - 20, height / 2];

var svg = d3.select("body").selectAll("svg")
    .data([
      [p0], // single point
      [p0, p1], // separating vertical line (|)
      [p1, p0], // separating vertical line (|)
      [p0, p2], // separating horizontal line (-)
      [p2, p0], // separating horizontal line (-)
      [p0, p3], // separating diagonal line (/)
      [p3, p0], // separating diagonal line (/)
      [p1, p2], // separating diagonal line (\)
      [p2, p1], // separating diagonal line (\)
      [p0, p3, p4], // collinear, separating diagonal lines (/)
      [p0, p4, p3], // collinear, separating diagonal lines (/)
      [p3, p0, p4], // collinear, separating diagonal lines (/)
      [p3, p4, p0], // collinear, separating diagonal lines (/)
      [p4, p0, p3], // collinear, separating diagonal lines (/)
      [p4, p3, p0], // collinear, separating diagonal lines (/)
      [p1, p2, p4], // collinear, separating diagonal lines (\)
      [p1, p4, p2], // collinear, separating diagonal lines (\)
      [p2, p1, p4], // collinear, separating diagonal lines (\)
      [p2, p4, p1], // collinear, separating diagonal lines (\)
      [p4, p1, p2], // collinear, separating diagonal lines (\)
      [p4, p2, p1], // collinear, separating diagonal lines (\)
      [p5, p4, p6], // collinear, separating horizontal lines (-)
      [p5, p6, p4], // collinear, separating horizontal lines (-)
      [p4, p5, p6], // collinear, separating horizontal lines (-)
      [p4, p6, p5], // collinear, separating horizontal lines (-)
      [p6, p4, p5], // collinear, separating horizontal lines (-)
      [p6, p5, p4], // collinear, separating horizontal lines (-)
      [p4, p7, p8], // collinear, separating vertical lines (|)
      [p4, p8, p7], // collinear, separating vertical lines (|)
      [p7, p4, p8], // collinear, separating vertical lines (|)
      [p7, p8, p4], // collinear, separating vertical lines (|)
      [p8, p4, p7], // collinear, separating vertical lines (|)
      [p8, p7, p4], // collinear, separating vertical lines (|)
      [p0, p1, p2, p3] // squares
    ])
  .enter().append("svg")
    .attr("width", width)
    .attr("height", height);

var g = svg.selectAll("g")
    .data(function(points) { return points; })
  .enter().append("g")
    .style("fill", function(point, i) { return color(i); });

g.append("path")
    .data(voronoi)
    .attr("d", function(polygon) { return "M" + polygon.join("L") + "Z"; });

g.append("circle")
    .attr("r", 2.5)
    .attr("transform", function(point) { return "translate(" + point + ")"; });

</script>

https://d3js.org/d3.v3.min.js