D3 Block-a-Day: Day 21, January 21st, 2017

D3 Block-a-Day: Day 21, January, 21th 2017

New Year's Resolution for 2017: Make a D3 Block a day to teach myself D3. This is Number 21. This example extends the January 11 Example Rhode Island click-to-zoom example to be a full chloropleth with the colors indicating number of tested students. The topoJSON files used to construct this visualization were created by me using shape files provided by the United States Census Bureau. The Center for Assessment makes these state and national school district topoJSON files available for anyone to use in their own development.

<!DOCTYPE html>
<meta charset="utf-8">
<head>
<title>D3 Block-a-Day: Day 11, January 11, 2017</title>
<style>

.background {
  fill: none;
  pointer-events: all;
}

#districts {
  fill: #ccc;
}

#districts .active {
  fill: orange;
}

#district-borders {
  fill: none;
  stroke: white;
  stroke-width: 1px;
  stroke-linejoin: round;
  stroke-linecap: round;
  pointer-events: none;
}

.hidden {
  display: none;
}

div.tooltip {
  background-color: #ffffff;
  padding: 7px;
  text-shadow: #f5f5f5 0 1px 0;
  font: 13px Helvetica Neue;
  border: 2.5px solid;
  border-color: black;
	border-radius: 3px;
  opacity: 0.9;
  position: absolute;
  box-shadow: rgba(0, 0, 0, 0.3) 0 2px 10px;
 }
</style>
</head>
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 600,
    centered;

var projection = d3.geoMercator()
			.center([ -71.5, 41.7 ])
			.scale(24000);

var path = d3.geoPath()
    .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", clicked);

var tooltip = d3.select('body').append('div')
      .attr('class', 'hidden tooltip');

var g = svg.append("g");

d3.json("RI_Districts.topojson", function(error, state_districts) {
  if (error) throw error;

g.append("g")
      .attr("id", "districts")
    .selectAll("path")
      .data(topojson.feature(state_districts, state_districts.objects.districts).features)
    .enter().append("path")
      .attr("d", path)
      .on("click", clicked)
      .on('mousemove', function(d) {
           var mouse = d3.mouse(svg.node()).map(function(d) {
                return parseInt(d);
         });
         tooltip.classed('hidden', false)
                .attr('style', 'left:' + (mouse[0] + 10) +'px; top:' + (mouse[1] - 20) + 'px')
                .html(d.properties.name);
         })
         .on('mouseout', function() {
                tooltip.classed('hidden', true);
         });;
  g.append("path")
      .datum(topojson.mesh(state_districts, state_districts.objects.districts, function(a, b) { return a !== b; }))
      .attr("id", "district-borders")
      .attr("d", path);
});

function clicked(d) {
  var x, y, k;

if (d && centered !== d) {
    var centroid = path.centroid(d);
    x = centroid[0];
    y = centroid[1];
    k = 4;
    centered = d;
  } else {
    x = width / 2;
    y = height / 2;
    k = 1;
    centered = null;
  }

g.selectAll("path")
      .classed("active", centered && function(d) { return d === centered; });

g.transition()
      .duration(750)
      .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")scale(" + k + ")translate(" + -x + "," + -y + ")")
      .style("stroke-width", 1.5 / k + "px");
}

</script>

https://d3js.org/d3.v4.min.js

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