Simple Choropleth - d3.carto.map

A simple choropleth map made with d3.carto.map.

After adding a topojson layer, you can access the features either by using map.layers() or the layer if assigned to a variable or via d3.selectAll.data() on the appropriate elements. You can then style the features based on their properties. In this case, the size of the ward.

Some hover behavior can also be defined using D3.

<html xmlns="https://www.w3.org/1999/xhtml">
<head>
  <title>d3.carto.map - Simple Chloropleth</title>
  <meta charset="utf-8" />
    <link type="text/css" rel="stylesheet" href="d3map.css" />
    <link type="text/css" rel="stylesheet" href="https://raw.githubusercontent.com/emeeks/d3-carto-map/master/examples/example.css" />
</head>
<style>
  html,body {
    height: 100%;
    width: 100%;
    margin: 0;
  }

#map {
    height: 100%;
    width: 100%;
    position: absolute;
  }
.wards {
    fill: gray;
    stroke: gray;
    stroke-width: 1px;
}
</style>
<script>
  function makeSomeMaps() {
    map = d3.carto.map();

d3.select("#map").call(map);
    
    map.mode("projection");

var projection = d3.geo.conicEquidistant()
    .center([-0.0275,51.307])
    .scale(84000)
    .translate(map.zoom().translate())
    .precision(.1);

map.projection(projection);
    map.refresh();
    
    topojsonLayer = d3.carto.layer();
    topojsonLayer
    .type("topojson")
    .path("glondon.topojson")
    .label("London Wards")
    .cssClass("wards")
    .renderMode("svg")
    .on("load", colorBySize);

map.addCartoLayer(topojsonLayer);
    
// Function is called on load because it won't have anything to apply to until the layer is loaded
    function colorBySize() {
    var featureData = topojsonLayer.features();
    var sizeExtent = d3.extent(featureData, function (d) {return d.properties.w_size})
    var sizeScale = d3.scale.quantile().domain(sizeExtent).range(colorbrewer.Greens[5]);

d3.selectAll("path.wards")
      .style("fill", function (d) {return sizeScale(d.properties.w_size)})
    
    //Some simple hover behavior
    d3.selectAll("path.wards").style("pointer-events", "auto").on("mouseover", wardOver).on("mouseout", wardOut);
    
    function wardOver(d,i) {
      d3.selectAll("path.wards").style("stroke-width", function (p) {return p.properties.region == d.properties.region ? 0 : 1})
    }

function wardOut(d,i) {
      d3.selectAll("path.wards").style("stroke-width", "1px")
    }

}

}
</script>
<body onload="makeSomeMaps()">
<div id="map"></div>
<footer>
<script src="https://d3js.org/d3.v3.min.js" charset="utf-8" type="text/javascript"></script>
<script src="https://d3js.org/topojson.v1.min.js" type="text/javascript">
</script>
<script src="https://d3js.org/d3.geo.projection.v0.min.js" type="text/javascript">
</script>
<script src="https://d3js.org/colorbrewer.v1.min.js"></script>
<script src="/emeeks/f3105fda25ff785dc5ed/example/tile.js" type="text/javascript">
</script>
<script src="/emeeks/f3105fda25ff785dc5ed/example/d3.quadtiles.js" type="text/javascript">
</script>
<script src="/emeeks/f3105fda25ff785dc5ed/example/d3.geo.raster.js" type="text/javascript">
</script>
<script src="https://cdn.jsdelivr.net/gh/emeeks/d3-carto-map/d3.carto.map.js" type="text/javascript">
</script>
</footer>
</body>
</html>

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

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

Modified http://d3js.org/d3.geo.projection.v0.min.js to a secure url

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

Updated missing url http://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/tile.js to /emeeks/f3105fda25ff785dc5ed/example/tile.js

Updated missing url http://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.quadtiles.js to /emeeks/f3105fda25ff785dc5ed/example/d3.quadtiles.js

Updated missing url http://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.geo.raster.js to /emeeks/f3105fda25ff785dc5ed/example/d3.geo.raster.js

Updated missing url https://rawgit.com/emeeks/d3-carto-map/master/d3.carto.map.js to https://cdn.jsdelivr.net/gh/emeeks/d3-carto-map/d3.carto.map.js

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

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

https://d3js.org/d3.geo.projection.v0.min.js

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

https://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/tile.js

https://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.quadtiles.js

https://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.geo.raster.js

https://rawgit.com/emeeks/d3-carto-map/master/d3.carto.map.js