Triangular Binning I

Triangular binning a set of 2D points. Maps color to the density of points within a triangle.

Essentially a fork of this block that does hexagonal binning. Uses the d3.triangleBin plugin. Also see this block which maps density to area instead of color.

<html>
  <head>
    <style>
      body {
        font: 12px sans-serif;
      }
      
      .axis path,
      .axis line {
        fill: none;
        stroke: #000;
      }
      
      .triangle {
        fill: none;
        stroke: #ddd;
        stroke-width: 0.5px;
      }
    </style>
  </head>
  <body>
     <script src="https://d3js.org/d3.v3.min.js" charset="utf-8"></script>
     <script src="triangle-bin.js"></script>
     <script>
       var margin = { top: 10, left: 40, bottom: 30, right: 10 },
           width = 960 - margin.left - margin.right,
           height = 500 - margin.top - margin.bottom;
           
       var points = d3.range(2000)
        .map(function() {
          return [
            d3.random.normal(width/2, 80)(),
            d3.random.normal(height/2, 80)()
          ];
        });
       
       var xScale = d3.scale.identity().domain([0, width]),
           yScale = d3.scale.linear()
            .domain([0, height])
            .range([height, 0]);
       
       var xAxis = d3.svg.axis().scale(xScale).orient("bottom"),
           yAxis = d3.svg.axis().scale(yScale).orient("left");
       
       var color = d3.scale.linear()
        .domain([0, 20])
        .range(["white", "steelblue"])
        .interpolate(d3.interpolateLab);
       
       var svg = d3.select("body").append("svg")
          .attr("width", width + margin.left + margin.right)
          .attr("height", height + margin.top + margin.bottom)
        .append("g")
          .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
       
       var tribin = d3.triangleBin()
        .size([width, height])
        .sideLength(35);
      
      svg.append("clipPath")
          .attr("id", "clip")
        .append("rect")
          .attr("width", width)
          .attr("height", height);
      
      svg.append("g")
          .attr("clip-path", "url(#clip)")
        .selectAll(".triangle")
          .data(tribin(points))
        .enter().append("path")
          .attr("class", "triangle")
          .attr("transform", function(d) {
           return "translate(" + d.x + "," + d.y + ")";
          })
          .attr("d", function(d) { return tribin.triangle(d.orientation); })
          .style("fill", function(d) { return color(d.length); });
      
      svg.append("g").call(xAxis)
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")");
      svg.append("g").call(yAxis)
        .attr("class", "y axis");
          
     </script>
  </body>
</html>

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