D3 Examples - Simple Choropleth

Simple Choropleth
This is not a true Demers cartogram; it lacks links between adjacent features. Instead of trying to preserve connectedness, this pseudo-cartogram tries to preserve locality, putting each square as close as possible to its origin without overlapping.
xxxxxxxxxx
 
<!DOCTYPE html>
<meta charset="utf-8">
<title>State Choropleth</title>
<style>
body {
  font-family: sans-serif;
}
  
.states {
  fill: url(#stripes);
  stroke: #fff;
}
    
text.legendtitle {
  font-weight: bold;
}
  
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script src="//d3js.org/queue.v1.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3-legend/1.10.0/d3-legend.min.js"></script>
<script>
console.clear()
​
var margin = {top: 50, right: 0, bottom: 20, left: 0},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;
​
var projection = d3.geo.albersUsa();
  
​
// create a geo path - https://github.com/mbostock/d3/wiki/Geo-Paths
var path = d3.geo.path();
 
// create an svg element
var svg = d3.select("body").append("svg")
            .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom),
    defs = svg.append("defs"),
    svgG = svg.append("g")
        .attr("transform", "translate(" + margin.left + "," + margin.top + ")" + 
                       "scale(" + Math.min(width / 960, height / 500) + ")");
 
// Set up a pattern for striping states with missing / no data
var stripes = defs.append("pattern")
  .attr("id", "stripes")
  .attr("width", 15)
  .attr("height", 10)
  .attr("patternUnits", "userSpaceOnUse")
  .attr("patternTransform", "rotate(45 50 50)")
​
stripes.append("line")
    .attr("stroke", "#d8d8d8")
    .attr("stroke-width", 10)
    .attr("y2", 20);
  
// create a container for states
var states = svgG.append("g")
    .attr("class", "states");
 
var colorScale = d3.scale.linear()
    .range(["steelblue", "white", "crimson"]);
​
svgG.append("g")
  .attr("class", "legendLinear")
  .attr("transform", "translate(" + (width - 150) + "," + (height - 100) + ")");
  
queue()
    .defer(d3.csv, "data.csv")
    .defer(d3.json, "us-state-centroids.json")
        .defer(d3.json, "us.json")
    .await(ready);
  
function ready(error, data, centroids, us) {
  if (error) throw error;
    
  //console.table(data); 
  colorScale.domain([
    d3.max(data, function(d) { return +d["2012D"]; }),
    0,
    -d3.max(data, function(d) { return +d["2012R"]; })
  ])
  
  var dataById = d3.map(data, function(d) { return +d.id; });
  
  
  // fill in all of the states at once
  // this uses the "states" class to stripe the background
  states.append("path")
      .attr("class", "states")
      .datum(topojson.feature(us, us.objects.states))
      .attr("d", path);
  
  // create paths for each state using the json data
  // and the geo path generator to draw the shapes
  states.selectAll(".state")
      .data(topojson.feature(us, us.objects.states).features
              .filter(function(d) { return dataById.has(+d.id); }))
    .enter().append("path")
      .attr("class", function(d) { return "state " + d.id; })
      .style("fill", function(d) { 
      var stateData = dataById.get(+d.id);
        console.log(d.id, stateData.code, stateData,
        stateData["2012D"] - stateData["2012R"])
        return colorScale(stateData["2012D"] - stateData["2012R"]); })
      .attr("d", path);
    
  var legendLinear = d3.legend.color()
    .shapeWidth(30)
    .cells([55, 30, 5, 0, -5, -20, -38])
    .title("Candidate (electoral votes)")
    .scale(colorScale);
​
  svgG.select(".legendLinear")
    .call(legendLinear);
  
};
​
</script>
​
    