Ch. 7, Fig. 19 - D3.js in Action

This is the code for Chapter 7, Figure 19 from D3.js in Action which shows how to use topojson.neighbors().

<html>
<head>
  <title>D3 in Action Chapter 7 - Example 9</title>
  <meta charset="utf-8" />
<script src="https://d3js.org/d3.geo.projection.v0.min.js" type="text/JavaScript"></script>
<script src="https://d3js.org/queue.v1.min.js" type="text/JavaScript"></script>
<script src="https://d3js.org/colorbrewer.v1.min.js" type="text/JavaScript"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js"></script>
</head>
<style>
  svg {
    height: 500px;
    width: 500px;
    border: 1px solid gray;
  }
  
  .countries {
    fill: red;
    fill-opacity: .5;
    stroke: black;
    stroke-width: 1px;
  }

</style>
<body>

<div id="viz">
  <svg>
  </svg>
</div>
</body>
  <footer>
    
<script>
    queue()
    .defer(d3.json, "world.topojson")
    .defer(d3.csv, "cities.csv")
    .await(function(error, file1, file2) { createMap(file1, file2); });
    
  function createMap(countries1, cities) {
    var countries = topojson.feature(countries1, countries1.objects.countries);
    var neighbors = topojson.neighbors(countries1.objects.countries.geometries);

width = 500;
    height = 500;
    projection = d3.geo.mollweide()
    .scale(120)
    .translate([width / 2, height / 2])
    .center([20,0])
    geoPath = d3.geo.path().projection(projection);
    
    featureSize = d3.extent(countries.features, function(d) {return geoPath.area(d)});
    countryColor = d3.scale.quantize().domain(featureSize).range(colorbrewer.Reds[7]);

var graticule = d3.geo.graticule();
    
    d3.select("svg").append("path")
    .datum(graticule)
    .attr("class", "graticule line")
    .attr("d", geoPath)
    .style("fill", "none")
    .style("stroke", "lightgray")
    .style("stroke-width", "1px");

d3.select("svg").append("path")
    .datum(graticule.outline)
    .attr("class", "graticule outline")
    .attr("d", geoPath)
    .style("fill", "none")
    .style("stroke", "black")
    .style("stroke-width", "1px");

d3.select("svg").selectAll("path.countries").data(countries.features)
    .enter()
    .append("path")
    .attr("d", geoPath)
    .attr("class", "countries")
    .style("fill", function(d) {return countryColor(geoPath.area(d))})
    .style("stroke-width", 1)
    .style("stroke", "black")
    .style("opacity", .5)
    .on("mouseover", centerBounds)
    .on("mouseout", clearCenterBounds)
    
    d3.select("svg").selectAll("circle").data(cities)
    .enter()
    .append("circle")
    .style("fill", "black")
    .style("stroke", "white")
    .style("stroke-width", 1)
    .attr("r", 3)
    .attr("cx", function(d) {return projection([d.y,d.x])[0]})
    .attr("cy", function(d) {return projection([d.y,d.x])[1]})
    
    function centerBounds(d,i) {
      d3.select(this).style("fill", "blue")
      d3.selectAll("path.countries").filter(function (p,q) {return neighbors[i].indexOf(q) > -1}).style("fill", "green")
    }
    function clearCenterBounds() {
      d3.selectAll("path.countries")
      .style("fill", function(d) {return countryColor(geoPath.area(d))})
      }
  }
  
</script>
  </footer>

</html>

Modified http://d3js.org/colorbrewer.v1.min.js to a secure url

https://d3js.org/d3.geo.projection.v0.min.js

https://d3js.org/queue.v1.min.js

https://d3js.org/colorbrewer.v1.min.js

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js

https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js