D3 Block-a-Day: Day 11, January 11th, 2017

D3 Block-a-Day: Day 11, January, 11th 2017

New Year's Resolution for 2017: Make a D3 Block a day to teach myself D3. This is Number 11. This example copies Mike Bostock's click-to-zoom via transform block and wires it up with the Rhode Island district shape file. 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.json", 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.District);
         })
         .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