Aggregate Value Graduated Hexbin

A graduated size and color hexbin that displays the total value of diamonds of a particular carat and depth from a dataset of 50k+ such diamonds. The style follows that of Scatterplot Matrix Techniques for Large N. Graduated hexbins that aggregate value do a better job of showing spatial distribution of values, as contrasted with graduated symbols that occlude each other as well as the region their purport to represent.

Here's a version that shows the raw number of items in each hex using the same color and symbology.

<!DOCTYPE html>

<html lang="en">
<head>
<meta charset="utf-8" />
<title>Aggregate Value Graduated Size and Color Hexbin</title>
<style>

svg {
  background: #3b7e77;
}
.node {
  stroke: #fff;
  stroke-width: 1.5px;
}

.link {
  fill: none;
  stroke: #000;
  stroke-width: 1.5px;
  opacity: 0.4;
  marker-end: url(#end-arrow);
}

.domain {
  fill: none;
  stroke: #5ba8b8;
}

.tick > line {
  stroke: #5ba8b8;
}

.tick > text {
  fill: #5ba8b8;
}

</style>
</head>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.16/d3.min.js" charset="utf-8" type="text/javascript"></script>
<script src="d3.hexbin.js" charset="utf-8" type="text/javascript"></script>
<script>

var xAtt = "carat";
var yAtt = "depth";
var hexsize = 5;

bgColors = d3.scale.threshold().domain([1,1000,100000,1000000,5000000]).range(["none","none","#0481ad","#39957c","#c18779"]);
fgColors = d3.scale.threshold().domain([1,1000,100000,1000000,5000000]).range(["none","#1d3b3d","#035c94","#386b5c","#363b37"]);

priceSizeScale = d3.scale.linear().domain([1,1000,1001,100000,100001,1000000,1000001,5000000]).range([0,hexsize,0,hexsize,0,hexsize,0,hexsize]);

//These attributes could be derived from the data
attributes = ["carat","depth","table","price","x","y","z"];

d3.csv("https://gist.githubusercontent.com/emeeks/613cd391ba7e9a3a4042/raw/5c3711f9e3f55bea40ce21f765dc373a28cf72de/diamonds.csv", hexbin);

d3.select("body").append("svg").attr("height", 850).attr("width", 800)

function hexbin(data) {

//d3.csv pulls in data as strings so they need to be formatted as numbers
  data.forEach(function (d) {
    attributes.forEach(function (att) {
      d[att] = parseFloat(d[att])
    })
  })

xExtent = d3.extent(data, function (d) {return d[xAtt]});
  xScale = d3.scale.linear();
  xScale.domain(xExtent).range([20,995]);

yExtent = d3.extent(data, function (d) {return d[yAtt]});
  console.log(yExtent)
  yScale = d3.scale.linear();
  yScale.domain(yExtent).range([995,20]);

var hexbin = d3.hexbin()
    .size([1000,1000])
    .x(function (d) {return xScale(d[xAtt])})
    .y(function (d) {return yScale(d[yAtt])})
    .radius(hexsize);

//bind the matrix array to a grid of g elements
  d3.select("svg")
  .append("g")
  .attr("class", "hexbin")
  .attr("transform", function (d) {return "translate(30,-200)" });

d3.select("g")
    .selectAll("path.bg")
    .data(hexbin(data))
    .enter()
    .append("path")
    .style("fill", function (d) {return bgColors(d3.sum(d, function (d) {return d.price}))})
    .style("stroke", function (d) {return bgColors(d3.sum(d, function (d) {return d.price}))})
    .attr("d", function(d) { return hexbin.hexagon(hexsize); })
    .attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; });

d3.select("g")
    .selectAll("path.fg")
    .data(hexbin(data))
    .enter()
    .append("path")
    .style("fill", function (d) {return fgColors(d3.sum(d, function (d) {return d.price}))})
    .style("stroke", function (d) {return fgColors(d3.sum(d, function (d) {return d.price}))})
    .attr("d", lastNumber)
    .attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; });

yAxis = d3.svg.axis()
.scale(yScale)
.orient("left")
.ticks(10)
.tickSize(0)
.tickSubdivide(true);

xAxis = d3.svg.axis()
.scale(xScale)
.orient("bottom")
.ticks(10)
.tickSize(0)
.tickSubdivide(true);

d3.select("g.hexbin").append("g").call(yAxis)

d3.select("g.hexbin").append("g").attr("transform", "translate(0,1000)").call(xAxis)

function lastNumber(d) {

var sl = d3.sum(d, function (d) {return d.price});

return hexbin.hexagon(priceSizeScale(sl));
}

}

</script>
</body>
</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.16/d3.min.js