Merging Counties III by mbostock

index.html

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

.land {
  fill: #eee;
}

.border--counties {
  fill: none;
  stroke: #fff;
}

.land--counties {
  fill-opacity: .2;
  stroke-linejoin: round;
  stroke-linecap: round;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 600;

var color = d3.scale.category10();

var projection = d3.geo.albersUsa()
    .scale(1280)
    .translate([width / 2, height / 2]);

var path = d3.geo.path()
    .projection(projection);

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

d3.json("/mbostock/raw/4090846/us.json", function(error, us) {
  if (error) throw error;

  svg.append("path")
      .datum(topojson.feature(us, us.objects.land))
      .attr("class", "land")
      .attr("d", path);

  svg.append("path")
      .datum(topojson.mesh(us, us.objects.counties, function(a, b) { return a !== b; }))
      .attr("class", "border border--counties")
      .attr("d", path);

  (function transition() {
    var g = svg.append("g")
        .datum(topojson.merge(us, us.objects.counties.geometries.filter(function() { return Math.random() > .5; })))
        .attr("class", "land--counties")
        .style("opacity", 0);

    g.selectAll("path")
        .data(function(d) { return d.coordinates; })
      .enter().append("path")
        .datum(function(d) { return {type: "Polygon", coordinates: d}; })
        .style("fill", function(d, i) { return color(i); })
        .style("stroke", function(d, i) { return d3.lab(color(i)).darker(); })
        .attr("d", path);

    g.transition()
        .duration(750)
        .style("opacity", 1)
      .transition()
        .duration(2500)
      .transition()
        .duration(750)
        .style("opacity", 0)
        .each("end", transition)
        .remove();
  })();
});

d3.select(self.frameElement).style("height", height + "px");

</script>