block by nitaku be2316fc1b32862ede5388b646694393

World map VII - continents

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Merging Natural Earth‘s countries dataset to create a map of continents yields a map that does not correspond to any of the alternatives listed by Wikipedia for subdividing the world into continents.

This map is similar to the 7 continents convention, but it portrays the Russian Federation and French Guyana (plus many small islands) as part of Europe. A curious continent called “Seven seas (open ocean)”, grouping a few islands, can also be found in the dataset.

index.js

// Generated by CoffeeScript 1.10.0
(function() {
  var CONTINENTS, color, contents, graticule, height, lod, path, projection, svg, width, zoom, zoomable_layer;

  svg = d3.select('svg');

  width = svg.node().getBoundingClientRect().width;

  height = svg.node().getBoundingClientRect().height;

  CONTINENTS = ['North America', 'Africa', 'South America', 'Asia', 'Europe', 'Oceania', 'Seven seas (open ocean)', 'Antarctica'];

  zoomable_layer = svg.append('g');

  zoom = d3.zoom().scaleExtent([-Infinity, Infinity]).on('zoom', function() {
    zoomable_layer.attrs({
      transform: d3.event.transform
    });
    zoomable_layer.selectAll('.label > text').attrs({
      transform: "scale(" + (1 / d3.event.transform.k) + ")"
    });
    return lod(d3.event.transform.k);
  });

  svg.call(zoom);

  projection = d3.geoWinkel3().rotate([0, 0]).center([0, 0]).scale((width - 3) / (2 * Math.PI)).translate([width / 2, height / 2]);

  path = d3.geoPath(projection);

  graticule = d3.geoGraticule();

  color = d3.scaleOrdinal(d3.schemeCategory10).domain(CONTINENTS);

  zoomable_layer.append('path').datum(graticule.outline()).attrs({
    "class": 'sphere_fill',
    d: path
  });

  contents = zoomable_layer.append('g');

  zoomable_layer.append('path').datum(graticule).attrs({
    "class": 'graticule',
    d: path
  });

  zoomable_layer.append('path').datum(graticule.outline()).attrs({
    "class": 'sphere_stroke',
    d: path
  });

  d3.json('ne_50m_admin_0_countries.topo.json', function(geo_data) {
    var continents, continents_data, en_continents, en_labels, labels, labels_data;
    continents_data = CONTINENTS.map(function(d) {
      var geometry;
      geometry = topojson.merge(geo_data, geo_data.objects.countries.geometries.filter(function(c) {
        return c.properties.continent === d;
      }));
      return {
        geometry: geometry,
        centroid: projection(d3.geoCentroid(geometry)),
        id: d
      };
    });
    labels_data = [];
    continents_data.forEach(function(d) {
      if (d.geometry.type === 'Polygon') {
        return labels_data.push(d);
      } else if (d.geometry.type === 'MultiPolygon') {
        return d.geometry.coordinates.forEach(function(p) {
          return labels_data.push({
            geometry: {
              coordinates: p,
              properties: d.properties,
              type: 'Polygon'
            },
            id: d.id
          });
        });
      }
    });
    labels_data.forEach(function(d) {
      return d.area = d3.geoArea(d.geometry);
    });
    continents = contents.selectAll('.continent').data(continents_data);
    en_continents = continents.enter().append('path').attrs({
      "class": 'continent',
      d: function(d) {
        return path(d.geometry);
      },
      fill: function(d) {
        return color(d.id);
      }
    });
    en_continents.append('title').text(function(d) {
      return d.id;
    });
    labels = contents.selectAll('.label').data(labels_data);
    en_labels = labels.enter().append('g').attrs({
      "class": 'label',
      transform: function(d) {
        var ref, x, y;
        ref = projection(d3.geoCentroid(d.geometry)), x = ref[0], y = ref[1];
        return "translate(" + x + "," + y + ")";
      }
    });
    en_labels.append('text').text(function(d) {
      return d.id;
    });
    return lod(1);
  });

  lod = function(z) {
    return zoomable_layer.selectAll('.label').classed('hidden', function(d) {
      return d.area < Math.pow(0.2 / z, 2);
    });
  };

}).call(this);

index.html

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>World map VII - continents</title>
  <link type="text/css" href="index.css" rel="stylesheet"/>
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <script src="https://d3js.org/d3-selection-multi.v0.4.min.js"></script>
  <script src="https://d3js.org/d3-geo-projection.v2.min.js"></script>
  <script src="//d3js.org/topojson.v2.min.js"></script>
</head>
<body>
  <svg></svg>
  <script src="index.js"></script>
</body>
</html>

index.coffee

svg = d3.select 'svg'
width = svg.node().getBoundingClientRect().width
height = svg.node().getBoundingClientRect().height

CONTINENTS = ['North America', 'Africa', 'South America', 'Asia', 'Europe', 'Oceania', 'Seven seas (open ocean)', 'Antarctica']

# ZOOM
zoomable_layer = svg.append 'g'

zoom = d3.zoom()
  .scaleExtent [-Infinity, Infinity]
  .on 'zoom', () ->
    zoomable_layer
      .attrs
        transform: d3.event.transform
        
    # SEMANTIC ZOOM
    # scale back all objects that have to be semantically zoomed
    zoomable_layer.selectAll '.label > text'
      .attrs
        transform: "scale(#{1/d3.event.transform.k})"
        
    # LOD & OVERLAPPING
    lod(d3.event.transform.k)
    
svg.call(zoom)

# PROJECTION
projection = d3.geoWinkel3()
  .rotate [0, 0]
  .center [0, 0]
  .scale (width - 3) / (2 * Math.PI)
  .translate [width/2, height/2]
path = d3.geoPath projection

# GRATICULE and OUTLINE
graticule = d3.geoGraticule()

# COLORS
color = d3.scaleOrdinal(d3.schemeCategory10)
  .domain CONTINENTS

zoomable_layer.append 'path'
  .datum graticule.outline()
  .attrs
    class: 'sphere_fill'
    d: path

contents = zoomable_layer.append 'g'

zoomable_layer.append 'path'
  .datum graticule
  .attrs
    class: 'graticule'
    d: path

zoomable_layer.append 'path'
  .datum graticule.outline()
  .attrs
    class: 'sphere_stroke'
    d: path

d3.json 'ne_50m_admin_0_countries.topo.json', (geo_data) ->
    continents_data = CONTINENTS.map (d) ->
      geometry = topojson.merge(geo_data, geo_data.objects.countries.geometries.filter (c) -> c.properties.continent is d)
      return {
        geometry: geometry
        centroid: projection d3.geoCentroid(geometry)
        id: d
      }
    
    # label each polygon instead of each multipolygon (to help with islands etc.)
    labels_data = []
    
    continents_data.forEach (d) ->
      if d.geometry.type is 'Polygon'
        labels_data.push d
      else if d.geometry.type is 'MultiPolygon'
        d.geometry.coordinates.forEach (p) ->
          labels_data.push {
            geometry: {
              coordinates: p
              properties: d.properties
              type: 'Polygon'
            }
            id: d.id
          }
    
    # compute area to aid label hiding
    labels_data.forEach (d) -> d.area = d3.geoArea(d.geometry)
    
    # continents
    continents = contents.selectAll '.continent'
      .data continents_data
      
    en_continents = continents.enter().append 'path'
      .attrs
        class: 'continent'
        d: (d) -> path d.geometry
        fill: (d) -> color d.id
        
    en_continents.append 'title'
      .text (d) -> d.id
      
    # labels
    labels = contents.selectAll '.label'
      .data labels_data
      
    en_labels = labels.enter().append 'g'
      .attrs
        class: 'label'
        transform: (d) ->
          [x,y] = projection d3.geoCentroid(d.geometry)
          return "translate(#{x},#{y})"
    
    en_labels.append 'text'
      .text (d) -> d.id
      
    # lod
    lod(1)
      
lod = (z) ->
  zoomable_layer.selectAll '.label'
    .classed 'hidden', (d) -> d.area < Math.pow(0.2/z,2)

index.css

body, html {
  padding: 0;
  margin: 0;
  height: 100%;
}
svg {
  width: 100%;
  height: 100%;
  background: white;
}

.sphere_stroke {
  fill: none;
  stroke: black; 
  stroke-width: 2px;
  vector-effect: non-scaling-stroke;
}

.sphere_fill {
  fill: white;
}

.graticule {
  fill: none;
  stroke: #777;
  stroke-width: 0.5px;
  stroke-opacity: 0.5;
  vector-effect: non-scaling-stroke;
  pointer-events: none;
}

.continent {
  fill-opacity: 0.3;
  stroke: white;
  stroke-width: 0.5;
  vector-effect: non-scaling-stroke;
}
.continent:hover {
  fill-opacity: 0.6;
}

.label {
  font-family: sans-serif;
  font-size: 10px;
  pointer-events: none;
  text-anchor: middle;
}
.label.hidden {
  display: none;
}