6. Scatter plot matrix using d3

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

svg {
  font: 10px sans-serif;
  padding: 10px;
}

.axis,
.frame {
  shape-rendering: crispEdges;
}

.axis line {
  stroke: #ddd;
}

.axis path {
  display: none;
}

.cell text {
  font-weight: bold;
  text-transform: capitalize;
}

.frame {
  fill: none;
  stroke: #aaa;
}

circle {
  fill-opacity: .7;
}

circle.hidden {
  fill: #ccc !important;
}

</style>
<body>

<script src="https://d3js.org/d3.v4.min.js"></script>
<script>

var width = 960,
    size = 230,
    padding = 30;

var x = d3.scaleLinear()
    .range([padding / 2, size - padding / 2]);

var y = d3.scaleLinear()
    .range([size - padding / 2, padding / 2]);

var gxScale = d3.scaleBand()
    .range([padding / 2, size - padding / 2]);

var gyScale = d3.scaleBand()
        .range([size - padding / 2, padding / 2])

color = d3.scaleOrdinal(d3.schemeCategory20);

d3.csv("billionaires.csv", function(error, data) {
  if (error) throw error;

var domainByTrait = {},
      traits = d3.keys(data[0]).filter(function(d) { return d == "gender" || d == "age" || d == "worth in billions"; }),
      n = traits.length;
  console.log(traits);

traits.forEach(function(trait) {
    if(trait == "gender"){
      domainByTrait[trait] = data.map(function(d) { return d['gender']; })
    }else {
      domainByTrait[trait] = d3.extent(data, function(d) {
      return +d[trait]; });
    }
  });

var svg = d3.select("body").append("svg")
      .attr("width", size * n + padding)
      .attr("height", size * n + padding)
    .append("g")
      .attr("transform", "translate(" + padding + "," + padding / 2 + ")");

// X axes
  svg.selectAll(".x.axis")
      .data(traits)
    .enter().append("g")
      .attr("class", "x axis")
      .attr("transform", function(d, i) { return "translate(" + ((n - i - 1) * size) + ",0)"; })
      .each(function(d) {
        if (d == "gender"){
          gxScale.domain(domainByTrait[d]);
          d3.select(this).call(d3.axisTop(gxScale));
        } else {
          x.domain(domainByTrait[d]);
          d3.select(this).call(d3.axisTop(x).ticks(5));
        }
      });
// Y axes
  svg.selectAll(".y.axis")
      .data(traits)
    .enter().append("g")
      .attr("class", "y axis")
      .attr("transform", function(d, i) { return "translate(0," + i * size + ")"; })
      .each(function(d) {
        if (d == "gender"){
          gyScale.domain(domainByTrait[d]);
          d3.select(this).call(d3.axisLeft(gyScale));
        } else {
          y.domain(domainByTrait[d]); d3.select(this).call(d3.axisLeft(y).ticks(5));
        }
      });

var cell = svg.selectAll(".cell")
      .data(cross(traits, traits))
    .enter().append("g")
      .attr("class", "cell")
      .attr("transform", function(d) { return "translate(" + ((n - d.i - 1) * size) + "," + (d.j * size) + ")"; })
      .each(plot)

// Titles for the diagonal.
  cell.filter(function(d) { return d.i === d.j; }).append("text")
      .attr("x", padding)
      .attr("y", padding)
      .attr("dy", ".71em")
      .text(function(d) { return d.x; });

function plot(p) {
    var cell = d3.select(this);

x.domain(domainByTrait[p.x]);
    y.domain(domainByTrait[p.y]);

cell.append("rect")
        .attr("class", "frame")
        .attr("x", padding / 2)
        .attr("y", padding / 2)
        .attr("width", size - padding)
        .attr("height", size - padding);

cell.selectAll("circle")
        .data(data)
      .enter().append("circle")
        .attr("cx", function(d) {
          console.log(p.x);
          if(p.x == "gender"){
            console.log("in gen", p.x);
            return gxScale(d[p.x]);
          }else {
            return x(d[p.x]);
          }
        })
        .attr("cy", function(d) {
          if(p.y == "gender"){
            return gyScale(d[p.y]);
          }else {
            return y(d[p.y]);
          }
        })
        .attr("r", 2)
        .style("fill", function(d) { return color(d.gender); });
  }

function cross(a, b) {
  var c = [], n = a.length, m = b.length, i, j;
  for (i = -1; ++i < n;) for (j = -1; ++j < m;) c.push({x: a[i], i: i, y: b[j], j: j});
  return c;
}
});
</script>
<p><a href = "https://bl.ocks.org/mbostock/3213173">Reference</a>
  </p>
</body>

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