D3 Examples - Bivariate cartogram

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<!DOCTYPE html>
<meta charset="utf-8">
​
<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>
<script src="https://d3js.org/d3-scale-chromatic.v1.min.js"></script>
<script src="https://d3js.org/d3-geo-projection.v2.min.js"></script>
<style>
  body { background-color: #fff; }
</style>
<svg id="cartogram" width="800" height="500"></svg>
​
<script>
​
// The svg
var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height");
​
// Map and projection
var projection = d3.geoMercator()
    .scale(600) // This is the zoom
    .translate([1500, 750]); // You have to play with these values to center your map
    
// Path generator
var path = d3.geoPath()
    .projection(projection)
​
// Colors
var lowColor = '#ffffff'
var highColor = '#bc2a66'
​
// load in the data
d3.queue()
    .defer(d3.json, "us_states_hexgrid.geojson")
    .defer(d3.csv, "sn.csv")
    .await(ready);
​
function ready(error, geo, sn) {
  if (error) throw error;
​
  // get min/max of everything
  var getArray = function(data,name) {
    var dataArray = [];
    for (var d = 0; d < data.length; d++) {
        dataArray.push(parseInt(data[d][name]))
    }
    return dataArray
  }
  var min1 = d3.min(getArray(sn,'population'))
  var max1 = d3.max(getArray(sn,'population'))
  var min2 = d3.min(getArray(sn,'avg_sn'))
  var max2 = d3.max(getArray(sn,'avg_sn'))
  
  // create color scale
  var colorRamp = d3.scaleSqrt()
    .domain([min2,max2])
    .range([lowColor,highColor])
  
  // Join geojson and CSV (gotta be a better way of doing this)
  for (var i = 0; i < sn.length; i++) {
    // Grab State Name
    var dataState = sn[i].state;
    // Grab grouped record count 
    var dataPop = sn[i].population;
    var dataSn = sn[i].avg_sn
    // Find the corresponding state inside the GeoJSON
    for (var j = 0; j < geo.features.length; j++) {
      var geoState = geo.features[j].properties.abbrv;
      if (dataState == geoState) {
        // Copy the data value into the JSON
        geo.features[j].properties.population = parseInt(dataPop);
        geo.features[j].properties.avg_sn = parseInt(dataSn);
        // Stop looking through the JSON
        break;
      }
    }
  }
      
  // Draw the scaled features
  svg.append("g")
      .selectAll("path")
      .data(geo.features)
      .enter()
      .append("path")
          .attr("fill", function(d) { return colorRamp(d.properties.avg_sn) || 'rgba(255,255,255,0.2)' })
          .attr("d", path)
          .attr("stroke", "rgba(100,100,100,0.9)")
          // create resize scale (via https://bl.ocks.org/rveciana/5928736)
          .attr("transform", function(d) {
            scale_factor = Math.sqrt(d.properties.population/(max1-min1));
            var centroid = path.centroid(d),
                x = centroid[0],
                y = centroid[1];
            return "translate(" + x + "," + y + ")"
                + "scale(" + scale_factor + ")"
                + "translate(" + -x + "," + -y + ")";
          });
          
  // Draw the mesh
  svg.append("g")
      .selectAll("path")
      .data(geo.features)
      .enter()
      .append("path")
          .attr("fill", "none")
          .attr("d", path)
          //.attr("stroke", "rgba(50,50,50,0.2)")
​
  // Add the labels
  svg.append("g")
      .selectAll("labels")
      .data(geo.features)
      .enter()
      .append("text")
        .attr("x", function(d){return path.centroid(d)[0]})
        .attr("y", function(d){return path.centroid(d)[1]})
        .text(function(d){ return d.properties.abbrv})
        .attr("text-anchor", "middle")
        .attr("alignment-baseline", "central")
        .style("font-size", 11)
        .style("fill", "rgba(25,25,25,0.6)")
        .attr("transform","translate(0,-15)")
}
​
</script>
    