Zoomable US States

Click a state to zoom and display counties. An extension of this block by Mike Bostock.

The color darker the greater the location quotient for employment in some industry (I forget what industry). The purpose of the example is to test out zoom functionality not to show data. That being said, the data is from the Bureau of Labor Statistics' QCEW survey.

<html>
<head>
  <title>Zoomable US States</title>
  <style>
    .background {
      fill: none;
      pointer-events: all;
    }

.state-land {
      fill: #b6a3d5;
      stroke-width: 1.5px;
      stroke: white;
    }

.county-land {
      stroke: white;
      stroke-width: .3px;
    }
  </style>
</head>
<body>

var color = d3.scale.sqrt()
    .range(['#a290be',' #6f9570'])
    .interpolate(d3.interpolateLab);

var projection = d3.geo.albersUsa()
    .scale(1080)
    .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);

svg.append('rect')
    .attr('class', 'background')
    .attr('width', width)
    .attr('height', height)
    .on('click', reset);

var map = svg.append('g')
    .style('stroke-width', '1.5px');

d3.csv('countyData.csv', function(error, countyData) {
    if (error) throw error;
    d3.json('us.json', function(error, topology) {
      if (error) throw error;

countyData = countyData.map(function(d) {
        return {
          id: +d.area_fips,
          lq: +d.emp_lq
        };
      });

color.domain(d3.extent(countyData, function(d) { return d.lq; }));

map.selectAll('.state-land')
          .data(topojson.feature(topology, topology.objects.states).features)
        .enter().append('path')
          .attr('d', path)
          .attr('class', 'state-land')
          .on('click', function(state) {
            clickState.call(this, state, topology, countyData);
          });
    });
  });

function clickState(state, topology, countyData) {
    if (active.node() == this) return reset();
    active.classed('active', false);
    active = d3.select(this).classed('active', true);

var bounds = path.bounds(state),
        dx = bounds[1][0] - bounds[0][0],
        dy = bounds[1][1] - bounds[0][1],
        x = (bounds[0][0] + bounds[1][0])/2,
        y = (bounds[0][1] + bounds[1][1])/2,
        scale = .9 / Math.max(dx / width, dy / height),
        translate = [width / 2 - scale * x, height / 2 - scale * y];

map.transition().duration(750)
      .style('stroke-width', 1.5 / scale + 'px')
      .attr('transform', 'translate(' + translate +')scale(' + scale + ')');

var counties = map.selectAll('.county-land')
        .call(drawCounties, topology, state.id, countyData);
  }

function drawCounties(selection, topology, stateFips, countyData) {

// Copy the GeometryCollection object (don't want to pass reference)
    var countiesGeo = Object.create(topology.objects.counties);

// Filter down to the counties within active state
    countiesGeo.geometries = topology.objects.counties.geometries
      .filter(function(county) {
        return fipsMatch(county.id, stateFips);
      });

var counties = selection
      .data(topojson.feature(topology, countiesGeo).features)

counties.enter().append('path')
      .attr('class', 'county-land')
      .on('click', reset);

counties
        .attr('opacity', 0)
        .attr('d', path)
        .style('fill', function(d) {
          var lq = countyData
            .filter(function(county) { return county.id === d.id; })
            .map(function(county) { return county.lq; });
          return color(lq);
        })
      .transition().duration(750)
        .attr('opacity', 1);

counties.exit()
      .transition().duration(750)
        .attr('opacity', 0)
        .remove();
  }

function reset() {
    active.classed('active', false);
    active = d3.select(null);

map
      .transition().duration(750)
        .style("stroke-width", "1.5px")
        .attr("transform", "");

map.selectAll('.county-land')
      .transition().duration(750)
        .attr('opacity', 0)
        .remove();
  }

function fipsMatch(countyFips, stateFips) {
    countyFips = String(countyFips);
    stateFips = String(stateFips);
    return countyFips.length === 5 ?
           countyFips.slice(0,2) === stateFips :
           countyFips.slice(0,1) === stateFips;
  }

</script>
</body>
</html>

Modified http://d3js.org/d3.v3.js to a secure url

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

https://d3js.org/d3.v3.js

https://d3js.org/topojson.v1.js