D3 Examples - Kentucky Population Density

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<!DOCTYPE html>
<meta charset="utf-8">
<head>
<style>
​
body {
  font-family: sans-serif;
}
​
svg {
  font: 10px sans-serif;
}
​
.caption {
  font-weight: bold;
  fill: #000;
}
​
.key path {
  display: none;
}
​
.key line {
  stroke: #000;
  shape-rendering: crispEdges;
}
​
#search-container {
  margin-left: 400px;
  margin-top: 25px;
  margin-bottom: 20px;
}
​
.description {
  width: 200px;
  height: 30px;
  margin-left: 280px;
  margin-top: -400px;
}
​
.county {
  fill: none;
}
​
.county-border {
  fill: none;
}
​
.state-border {
  fill: none;
}
​
</style>
<link href="./awesomplete.css" rel="stylesheet">
<script src="./awesomplete.min.js"></script>
</head>
<body>
<div id="search-container">
</div>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>
​
let width = 960,
    height = 600;
​
let color = d3.scaleThreshold()
    .domain([30, 60, 120, 360])
    .range(["#ffffcc","#c2e699","#78c679","#31a354","#006837"]);
​
// A position encoding for the key only.
let x = d3.scaleLinear()
    .domain([0, 390])
    .range([0, 240]);
​
let xAxis = d3.axisBottom()
    .scale(x)
    .tickSize(13)
    .tickValues(color.domain());
​
// Kentucky State Plane, Single Zone
// ftp://kygeonet.ky.gov/kygeodata/standards/Ky_StatePlane.pdf
let projection = d3.geoConicConformal()
    .rotate([85 + 45 / 60, -36 - 20 / 60])
    .parallels([37 + 05 / 60, 38 + 40 / 60])
    .scale(7090)
    .center([-0.04940, 0.906])
    .translate([width / 2, height / 2]);
​
let path = d3.geoPath()
    .projection(projection);
​
let svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", 500);
​
let g = svg.append("g")
    .attr("class", "key")
    .attr("transform", "translate(60,460)");
​
g.selectAll("rect")
    .data(color.range().map(function(d, i) {
      return {
        x0: i ? x(color.domain()[i - 1]) : x.range()[0],
        x1: i < color.domain().length ? x(color.domain()[i]) : x.range()[1],
        z: d
      };
    }))
  .enter().append("rect")
    .attr("height", 8)
    .attr("x", function(d) { return d.x0; })
    .attr("width", function(d) { return d.x1 - d.x0; })
    .style("fill", function(d) { return d.z; });
​
g.call(xAxis).append("text")
    .attr("class", "caption")
    .attr("text-anchor", "start")
    .attr("y", -6)
    .text("Population per square mile");
​
d3.json("ky-counties.json", function(error, ky) {
  if (error) throw error;
​
  let counties = topojson.feature(ky, ky.objects.counties),
      countyNames = counties.features.map(c => c.properties.name.replace(" County", "")).sort();
​
  let countyShapes = svg.append("g")
      .attr("class", "county")
      .selectAll("path")
      .data(counties.features)
      .enter().append("path")
      .attr("stroke", "#fff")
      .attr("stroke-width", 0.5);
​
    countyShapes
      .attr("d", path)
      .style("fill", function(d) { return color(d.density = d.properties.population / d.properties.area); });
​
    countyShapes
      .on("mouseover", function(d) {
​
          d3.select(".description").remove();
​
          countyShapes.attr("stroke", "#fff")
            .attr("stroke-width", 0.5);
​
          d3.select(this)
              .raise()
              .attr("stroke", "#000")
              .attr("stroke-width", 2.5);
​
          makeDescription(d);
      })
      .on("mouseout", function(d) {
          d3.select(this)
              .lower()
              .attr("stroke", "#fff")
              .attr("stroke-width", 0.5);
​
          d3.select(".description").remove();
      });
​
  handleSearching(countyNames, countyShapes);
​
  d3.select("#county-input").node().focus();
​
  svg.append("path")
      .datum(topojson.mesh(ky, ky.objects.counties, function(a, b) { return a === b; }))
      .attr("class", "state-border")
      .attr("d", path)
      .attr("stroke", "#777")
      .attr("stroke-width", 1)
      .lower();
​
  svg.append("path")
      .datum(topojson.mesh(ky, ky.objects.counties, function(a, b) { return a !== b; }))
      .attr("class", "county-border")
      .attr("d", path);
});
​
function makeDescription(d) {
​
  d3.select("body")
      .append("div")
      .attr("class", "description")
      .html(`<strong>${d.properties.name.replace(" County", "")}</strong>: ${d.density.toFixed(0)}/mi.²`);
}
​
function handleSearching(names, shapes) {
​
  d3.select("#search-container")
    .append("input")
    .attr("class", "awesomplete")
    .attr("id", "county-input")
    .attr("tabindex", "0")
    .property("placeholder", "Search by county");
​
  new Awesomplete(d3.select("#county-input").node(), {
        list: names
    });
​
  d3.select("#county-input")
        .on("awesomplete-selectcomplete", function() {
          let searchedCounty = shapes.filter(
              d => d.properties.name.replace(" County", "") === d3.select(this).property("value")
          );
​
          shapes
              .attr("stroke", "#fff")
              .attr("stroke-width", 0.5);
​
          searchedCounty
              .raise()
              .attr("stroke", "#000")
              .attr("stroke-width", 2.5);
​
          d3.select(".description").remove();
​
          makeDescription(searchedCounty.data()[0]);
​
          d3.select(this).property("value", "");
​
      })
      .on("blur", function() {
​
          shapes
              .attr("stroke", "#fff")
              .attr("stroke-width", 0.5);
​
          d3.select(".description").remove();
      });
}
​
</script>
​
    