D3 Examples - Geo Scatterplot Transitions

Geo Scatterplot Transitions
This is a design experiment for project project tomorrow. I used it as an proof of concept to grasp the usability for intermodal projections of global data. The sweet spots of the code are from Jason Davis Dorling World and Mike Bostocks Shape Tweening. Open the block in a sperate window for all of its functionality.
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​
<!DOCTYPE html>
<html lang="en">
<head>
<!--                                                    
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  .--.--.   \    /  \     /   /   \         ,--.'| 
 /  /    '. |   :    \   /   .     :    ,--,:  : | 
|  :  /`. / |   |  .\ : .   /   ;.  \,`--.'`|  ' : 
;  |  |--`  .   :  |: |.   ;   /  ` ;|   :  :  | | 
|  :  ;_    |   |   \ :;   |  ; \ ; |:   |   \ | : 
 \  \    `. |   : .   /|   :  | ; | '|   : '  '; | 
  `----.   \;   | |`-' .   |  ' ' ' :'   ' ;.    ; 
  __ \  \  ||   | ;    '   ;  \; /  ||   | | \   | 
 /  /`--'  /:   ' |     \   \  ',  / '   : |  ; .' 
'--'.     / :   : :      ;   :    /  |   | '`--'   
  `--'---'  |   | :       \   \ .'   '   : |       
            `---'.|        `---`     ;   |.'       
              `---`                  '---'         
                                                   
​
christopher pietsch, 2016
-->
​
<meta charset="utf-8">
<title>Earth globe</title>
<script src="https://zeigma.com/spon/globes/js/d3.v3.min.js"></script>
<script src="https://zeigma.com/spon/globes/js/d3.geo.projection.v0.min.js"></script>
<script src="https://zeigma.com/spon/globes/js/topojson.v1.min.js"></script>
<script src="https://zeigma.com/spon/globes/js/queue.v1.min.js"></script>
<script src="https://zeigma.com/spon/globes/js/colorbrewer.v1.min.js"></script>
<script src="https://zeigma.com/spon/globes/js/d3.geo.zoom.js"></script>
<script src="https://zeigma.com/spon/globes/js/d3-legend.js"></script>
<script src="https://zeigma.com/spon/globes/js/d3.tip.v0.6.3.js"></script>
</head>
<style type="text/css">
​
body {
  font-family: Helvetica;
}
​
svg {
    /*padding: 20px;*/
    clear: left;
    float: left;
}
​
.menu {
    float: left;
    padding: 20px;
}
​
.menu.side {
    width: 160px;
}
​
.menu .button {
  margin: 10px;
      padding: 0 16px;
  text-transform: uppercase;
  border: 1px solid #eee;
  float: left;
  position: relative;
  cursor: pointer;
  font-size: 12px;
  font-weight: bold;
  color:#000;
  background: rgba(158,158,158,.2);    
  box-shadow: 0 2px 2px 0 rgba(0,0,0,.14),0 3px 1px -2px rgba(0,0,0,.2),0 1px 5px 0 rgba(0,0,0,.12);
  border-radius: 2px;
  text-align: center;
  line-height: 36px;
  vertical-align: middle;
  min-width: 64px;
  height: 36px;
}
​
.menu .button2 {
margin: 10px;
    /* padding: 0 16px; */
    text-transform: uppercase;
    border: 1px solid #eee;
    float: left;
    position: relative;
    cursor: pointer;
    font-size: 12px;
    font-weight: bold;
    color: #000;
    background: rgba(158,158,158,.2);
    box-shadow: 0 2px 2px 0 rgba(0,0,0,.14),0 3px 1px -2px rgba(0,0,0,.2),0 1px 5px 0 rgba(0,0,0,.12);
    border-radius: 2px;
    text-align: center;
    /* line-height: 36px; */
    vertical-align: middle;
    min-width: 36px;
    /* height: 36px; */
}
.menu .button2 img {
​
}
​
.colors {
    position: relative;
    clear: left;
    padding: 20px;
    float: left;
}
.colors input {
    width: 60px;
    border: none;
    float: left;
    padding: 10px;
}
​
text.label {
    font-size: 12px;
}
​
.water {
  fill: none;
  stroke: #000;
}
.d2 .water {
  stroke: none;
}
​
.land {
  fill: #888;
  stroke: rgba(0, 0, 0, 0.35);
  stroke-width: 0.7px;
}
​
.land:hover {
  fill:red;
  stroke-width: 1px;
  cursor: pointer;
}
​
.focused {
  fill: #33CC33;
}
.graticule {
  fill:none;
  stroke:#EEE;
}
​
​
​
.noData{
  mask: url(#mask-stripe);
}
​
select {
  position: absolute;
  top: 20px;
  left: 580px;
  border: solid #ccc 1px;
  padding: 3px;
  box-shadow: inset 1px 1px 2px #ddd8dc;
}
​
​
.d3-tip {
  line-height: 1;
  font-weight: bold;
  padding: 12px;
  background: rgba(0, 0, 0, 0.8);
  color: #fff;
  border-radius: 2px;
}
​
/* Creates a small triangle extender for the tooltip */
.d3-tip:after {
  box-sizing: border-box;
  display: inline;
  font-size: 10px;
  width: 100%;
  line-height: 1;
  color: rgba(0, 0, 0, 0.8);
  content: "\25BC";
  position: absolute;
  text-align: center;
}
​
/* Style northward tooltips differently */
.d3-tip.n:after {
  margin: -1px 0 0 0;
  top: 100%;
  left: 0;
}
​
​
.palette {
    padding: 20px;
    float: left;
    width: 820px;
}
​
​
h4 {
    float: left;
    /* clear: left; */
    width: 100%;
}
​
.legendTitle  {
    font-weight: bold;
}
​
.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}
​
.axis text {
  font-size: 11px;
}
​
</style>
<body>
<svg>
  <defs>
    <pattern id="pattern-stripe" 
      width="4" height="4" 
      patternUnits="userSpaceOnUse"
      patternTransform="rotate(45)">
      <rect width="2" height="4" transform="translate(0,0)" fill="white"></rect>
    </pattern>
    <mask id="mask-stripe">
      <rect x="0" y="0" width="100%" height="100%" fill="url(#pattern-stripe)" />
    </mask>      
  </defs>
</svg>
  <script>
​
  var margin = {top: 20, right: 20, bottom: 40, left: 40},
      width = 700 - margin.left - margin.right,
      height = 600 - margin.top - margin.bottom,
      sens = 0.25,
      focused;
​
  var speed = -0.1,
      start = 0;
​
​
  var datasets = [
    {
      name: "Fleischkonsum pro Woche in kg",
      active: true,
      url : "meat.csv",
      unit: "kg"
    },
    {
      name: "Bevölkerungswachstum 2014 in %",
      active: false,
      url : "bevolkerung.csv",
      unit: "%"
    }
  ];
​
​
  var projections = [
    {
      name: "globe",
      active: true,
      initialScale: 245,
      clipAngle: 90,
      geo: d3.geo.orthographic()
            .scale(245)
            .rotate([0, 0])
            .translate([width / 2, height / 2])
            .clipAngle(90)
    },
    {
      name: "map",
      active: false,
      initialScale: (245/1.5),
      clipAngle: null,
      geo: d3.geo.winkel3()
            .scale(245/1.5)
            .translate([width / 2, height / 2])
            .rotate([0, 0])
    },
    {
      name: "map",
      active: false,
      initialScale: (245/2.5),
      clipAngle: null,
      geo: d3.geo.mercator()
            .scale(245/2.5)
            .translate([width / 2, height / 2])
            .rotate([0, 0])
    }
  ];
​
  var scales = [
    {
      name: "linear",
      scale: d3.scale.linear().range([0,width])
    },
    {
      name: "linear",
      scale: d3.scale.linear().range([height,0])
    }
  ];
​
  var state = {
    mode: "globe",
    projection: projections[0],
    dataset: datasets[0],
    scale: 1,
    translate: [0,0],
    play: false,
    x: scales[0],
    y: scales[1],
  }
​
​
  var xAxis = d3.svg.axis()
      .scale(state.x.scale)
      .orient("bottom");
​
  var yAxis = d3.svg.axis()
      .scale(state.y.scale)
      .orient("left")
      .tickFormat(d3.format("s"))
​
​
  var tip = d3.tip()
    .attr('class', 'd3-tip')
    .offset([-5, 0])
​
  var path = d3.geo.path()
    .projection(state.projection.geo);
​
  var scale = 1
  var translate = [0,60];
  var rotate;
​
  var zoom = d3.behavior.zoom()
    .center([0,0])
    .translate(translate)
    .on("zoom", function(d){
​
      scale = d3.event.scale;
      translate = d3.event.translate;
      rotate = state.projection.geo.rotate();
​
      // console.log("zoom", d3.event);
​
     state.projection.geo
        .rotate([(translate[0]/scale) * sens, -(translate[1]/scale) * sens, 0])
        .scale(state.projection.initialScale * d3.event.scale)
​
     inner
      .selectAll("path")
      .attr("d", function(d) { return d.geometry ? path(d.geometry) : path(d); });
​
    })
​
  var menu = d3.select("body").append("div").classed("menu", true).classed("side", true);
  var palette = d3.select("body").append("div").classed("palette", true);
  palette.append("h4").text("Farbskala")
  var colors = palette.append("div").classed("colors", true);
  var colorBrewer = palette.append("div").classed("menu", true);
​
  var playButton = menu
    .append("div")
    .classed("button", true)
    .text("Pause")
    .on("click", function(){
      var d = d3.select(this);
​
      if(d.text()=="Play"){
        state.play = true;
        d.text("Pause")
      } else {
        state.play = false;
        d.text("Play")
      }
    })
​
  menu
    .append("h4")
    .text("Ansichten")
​
  menu
    .append("div")
    .classed("button", true)
    .text("globus")
    .on("click", function(){
      transform2d(0);
    })
    // .append("img")
    // .attr("src", "img/globe.svg")
​
  menu
    .append("div")
    .classed("button", true)
    .text("karte")
    .on("click", function(){
      transform2d(1);
    })
    // .append("img")
    // .attr("src", "img/map.svg")
​
  menu
    .append("div")
    .classed("button", true)
    .text("Diagramm")
    .on("click", function(){
      transformScatter();
    })
    // .append("img")
    // .attr("src", "img/chart.svg")
​
  
​
  //setTimeout(transformScatter, 800);
​
​
  var graticule = d3.geo.graticule();
​
  var svg = d3.select("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
    .call(zoom)
    .call(tip)
    .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");
​
  var axis = svg.append("g").style("opacity", 0);
  var inner = svg.append("g");
  var outer = svg.append("g");
  
​
  outer.append("path")
    .datum({type: "Sphere"})
    .attr("class", "water")
    .attr("d", path)
    
​
  inner.append("path")
    .datum(graticule())
    .attr("class", "graticule")
    .attr("d", path);
​
  axis.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis)
      .append("text")
        .attr("class", "label")
        .attr("x", width)
        .attr("y", -6)
        .style("text-anchor", "end")
        // .text("fleischkonsum (kg/woche)");
​
  axis.append("g")
        .attr("class", "y axis")
        .call(yAxis)
      .append("text")
        .attr("class", "label")
        .attr("transform", "rotate(-90)")
        .attr("y", 6)
        .attr("dy", ".71em")
        .style("text-anchor", "end")
        // .text("population")
​
  
​
  var colorScaleAbs = d3.scale.quantile().range(colorbrewer.Oranges[9]);
  var colorScaleDiverging = d3.scale.quantile().range(colorbrewer.BrBG[9]);
​
  var colorScale;
  var dataMap;
​
  var reverseCountryMap = {};
  var isoCodesMap;
  var globalDataMap;
​
​
  var transform2d = function(id){
    console.log("transform");
​
    state.play = false;
    playButton.text("Play");
​
​
    if(id == 0){
      inner.selectAll(".graticule").transition().style("opacity", 1);
    }
    if(id == 1){
      outer.selectAll(".water").transition().style("opacity", 0);
    }
​
    if(state.mode == "scatter"){
      state.projection = projections[id];
      path.projection(state.projection.geo);
      state.mode = "map"+id;
​
      transformScatterBack();
      return;
    }
​
    state.mode = "map"+id;
​
    var b = projections[id];
    var a = projections[(id+1)>1 ? 0:1];
​
    svg
      .call(zoom.scale(scale).translate(translate).event)
      .transition()
      .duration(function() {
        var distance = (Math.abs(translate[0])+Math.abs(translate[1]));
        return distance*2;
      })
      .call(zoom.scale(1).translate([0,0]).event)
      .each("end", function(){
        
        inner.selectAll("path")
          .transition()
          .duration(1000)
          // .ease("circle-out")
          // .attrTween("d", projectionTween(active(projections).geo, inactive(projections).geo))
          .attrTween("d", geoUtils.projectionTween(a.geo, b.geo))
          .each("end", function(d,i){
            if(i!=0) return;
            
            state.projection = b;
            path.projection(state.projection.geo);
​
            if(id == 0){
              outer.selectAll(".water").transition().style("opacity", 1);
              //zoom.event(svg);
            }
            
          })
      })
​
    
   
  }
​
  var transformScatterBack = function (callback) {
​
    axis.transition().duration(1000).style("opacity", 0);
    //inner.selectAll(".graticule").transition().style("opacity", 1);
​
    inner.selectAll(".land")
      .transition()
      .ease("cubic-out")
      .duration(800)
      .attr("d", function (d) {
        return geoUtils.pathCircle(d.dorling.centroid[0], d.dorling.centroid[1], d.dorling.radius);
      })
      .each("end", function(d) {
        // console.log(d)
        d3.select(this).attr("d", "M" + d.dorling.coordinates.join("L") + "Z");
      })
      .transition()
      .duration(500)
      .ease("cubic")
      .attr("d", function(d) { return path(d.geometry); })
      .each("end",function (d,i) {
        if(i==0 && callback){
          console.log("end", i);
          callback();
        }
      })
    
  }
​
  var transformScatter = function(){
    console.log("transformScatter");
​
    state.mode = "scatter";
​
    state.projection.geo.clipAngle(null);
​
    outer.selectAll(".water").transition().style("opacity", 0);
    inner.selectAll(".graticule").transition().style("opacity", 0);
​
    axis.transition().duration(1000).style("opacity", 1);
​
    inner.selectAll(".land")
      .transition()
      .ease("cubic-out")
      .duration(800)
      .attr("d", function(d) {
        d.dorling = geoUtils.dorling(d.geometry);
        return "M" + d.dorling.coordinates.join("L") + "Z";
      })
      .each("end", function(d) {
        d = d.dorling;
        d3.select(this).attr("d", geoUtils.pathCircle(d.centroid[0], d.centroid[1], d.radius));
      })
      .transition()
      .duration(1500)
      .ease("cubic-out")
      .attr("d", function (d) {
        var yVal = globalDataMap.get(d.iso);
        var xVal = state.dataset.map.get(d.iso)
        // todo clean that data !!
        if(!yVal || !yVal.gdp || !xVal || !xVal.value){
          // return pathCircle(d.dorling.centroid[0], d.dorling.centroid[1], 0);
          return;
        };
      
        var x = state.x.scale(xVal.value);
        var y = state.y.scale(yVal.gdp);
​
        return geoUtils.pathCircle(x, y, 5)
      })
​
      state.projection.geo.clipAngle(state.projection.clipAngle);
​
​
  }
​
​
  queue()
    .defer(d3.json, "world-110m.json")
    // .defer(d3.json, "data/world-50m.json")
    .defer(d3.csv, "iso3166.csv")
    .defer(d3.csv, datasets[0].url)
    .defer(d3.csv, datasets[1].url)
    .await(ready);
​
  function ready(error, world, isoCodes, ds1, ds2) {
    datasets[0].data = ds1;
    datasets[0].data.forEach(function(d){ d.value *= 1; });
    datasets[0].map = d3.map(datasets[0].data, function(d){ return d.iso; });
​
    datasets[1].data = ds2;
    datasets[1].data.forEach(function(d){ d.value *= 1; });
    datasets[1].map = d3.map(datasets[1].data, function(d){ return d.iso; });
​
    isoCodes.forEach(function(d){ d.numeric *= 1; d.population *= 1; d.gdp *= 1; });
    isoCodesMap = d3.map(isoCodes, function(d){ return d.numeric; });
    globalDataMap = d3.map(isoCodes, function(d){ return d.alpha3; });
​
​
    // filter out antarctica
    world.objects.countries.geometries = world.objects.countries.geometries.filter(function(d) { return d.id != 10; });
    
    var land = {
      type: "GeometryCollection",
      geometries: geoUtils.polygons(world.objects.countries.geometries)
    };
​
    var nodes = topojson.feature(world, land).features.map(function(d) {
      //exterior(d.geometry);
      //var centroid = path.centroid(d.geometry);
      var iso = isoCodesMap.get(d.id);
​
      return {
        iso: reverseCountryMap[d.id],
        // x: centroid[0],
        // y: centroid[1],
        // ox: centroid[0],
        // oy: centroid[1],
        geometry: d.geometry,
        //dorling: dorling(d.geometry)
      };
    });
​
    console.log(nodes[0]);
​
​
​
    var populationExtent = d3.extent(datasets[1].data, function(d){ return d.value; });
    var max = Math.max(Math.abs(populationExtent[0]), Math.abs(populationExtent[1]));
    console.log(populationExtent, max);
​
    colorScaleDiverging
      .domain([-max,max])
​
    colorScaleAbs
      .domain([0, d3.max(datasets[0].data, function(d){ return d.value; })])
​
    colorScale = colorScaleAbs;
​
    var getColor = function(d){
      var entry = state.dataset.map.get(d.iso);
      return entry ? colorScale(entry.value) : "#B5B5B5";
    }
​
​
    state.x.scale.domain(d3.extent(state.dataset.data, function(d) { return d.value; }));
    state.y.scale.domain(d3.extent(isoCodes, function(d) { return d.gdp; }));
​
    axis.select(".x.axis").call(xAxis);
    axis.select(".y.axis").call(yAxis);
​
    //console.log(state.x.scale.domain());
​
    tip.html(function(d) {
      //console.log(d, isoCodesMap.get(d.id).name_deu,meatMap.get(d.iso).value)
      var map = state.dataset.map.get(d.iso);
      var val = map ? map.value : "n.v."
      return "<strong>"+ globalDataMap.get(d.iso).name_deu +"</strong> <span style='color:red'>" + val + "</span>";
    })
​
    var world = inner.selectAll("path.land")
      .data(nodes)
      .enter()
      .append("path")
      .attr("class", "land")
      .attr("d", function(d) { return path(d.geometry); })
      .style("fill", getColor)
      .classed("noData", function(d){ return !state.dataset.map.get(d.iso); })
      .on('mouseover', tip.show)
      .on('mousemove', tip.show)
      .on('mouseout', tip.hide)
​
    // var world = inner.selectAll("path.land")
    //   .data(countries)
    //   .enter()
    //   .append("path")
    //   .attr("class", "land")
    //   .attr("d", path)
    //   .style("fill", getColor)
    //   .classed("noData", function(d){ return !active(datasets).map.get(d.iso); })
      // .on('mouseover', tip.show)
      // .on('mousemove', tip.show)
      // .on('mouseout', tip.hide)
​
    var colorRange = colorScale.range();
​
    colors
      .selectAll("input")
      .data(colorRange)
      .enter()
      .append("input")
      .attr("value", function(d){ return d; })
      .style("background", function(d){ return d; })
      .on("input", function(d,i){
        d3.select(this).style("background",this.value);
        colorRange[i] = this.value;
        colorScale.range(colorRange);
​
        updateColors();
      })
​
    menu
    .append("h4")
    .text("Daten")
​
    menu
      .append("div")
      .classed("button", true)
      .text("Fleischkonsum")
      .on("click", function(){
        state.dataset = datasets[0];
​
        colorScale = colorScaleAbs;
        colorRange = colorScale.range();
​
        updateColors();
      })
​
    menu
      .append("div")
      .classed("button", true)
      .text("Bevölkerungswachstum")
      .on("click", function(){
        state.dataset = datasets[1];
​
        colorScale = colorScaleDiverging;
        colorRange = colorScale.range();
​
        updateColors();
      })
​
    var updateColors = function(){
      inner
        .selectAll("path.land")
        .classed("noData", function(d){ return !state.dataset.map.get(d.iso); })
        .transition()
        .style("fill", getColor)
​
      legend
        .scale(colorScale)
        .title(state.dataset.name)
​
      svg.select(".legendQuant")
        .call(legend);
​
      colors
        .selectAll("input")
        .data(colorRange)
        .style("background", function(d){ return d; })
        .attr("value", function(d){ return d; })
​
      state.x.scale.domain(d3.extent(state.dataset.data, function(d) { return d.value; }));
      state.y.scale.domain(d3.extent(isoCodes, function(d) { return d.gdp; }));
​
      axis.select(".x.axis").call(xAxis);
      axis.select(".y.axis").call(yAxis);
      
    }
​
    var cbrew = d3.entries(colorbrewer).filter(function(d){ return d.value[9]; });
​
    colorBrewer
      .selectAll("div")
      .data(cbrew)
      .enter()
      .append("div")
      .classed("button", true)
      .text(function(d){ return d.key; })
      .on("click", function(d){
        colorRange = colorbrewer[d.key][9];
        colorScale.range(colorRange)
​
        updateColors();
      })
​
    svg.append("g")
      .attr("class", "legendQuant")
      .attr("transform", "translate(10,10)");
​
    axis.select(".x.axis").call(xAxis);
    axis.select(".y.axis").call(yAxis);
​
    var legend = d3.legend.color()
      .labelFormat(d3.format(".2f"))
      .useClass(false)
      .labelFormat(function(d){ return d3.format("f")(d); })
      .scale(colorScale)
      //.orient("horizontal")
      .title("Fleischkonsum pro Woche in kg")
​
    svg.select(".legendQuant")
      .call(legend);
​
   zoom.event(svg);
​
   d3.timer(function() {
​
      if(state.play){
        // active(projections).geo
        //  .rotate([speed * start++, -15])
​
        // svg.selectAll("path").attr("d", path)
        zoom.translate([translate[0]+((5)*speed), translate[1]]).event(svg);
      }
​
  })
​
​
};
​
var geoUtils = {};
​
geoUtils.exterior = function(d) {
  // From Jason Davis https://www.jasondavies.com/maps/dorling-world/
  switch (d.type) {
    case "Polygon": d.coordinates = [d.coordinates[0]]; break;
    case "MultiPolygon": d.coordinates = [[d.coordinates[0][0]]]; break;
  }
  return d;
}
​
​
geoUtils.projectRing = function(coordinates) {
  // From Jason Davis https://www.jasondavies.com/maps/dorling-world/
  var ring = [];
  d3.geo.stream({type: "Polygon", coordinates: [coordinates]}, state.projection.geo.stream({
    point: function(x, y) { ring.push([x, y]); },
    lineStart: geoUtils.noop,
    lineEnd: geoUtils.noop,
    polygonStart: geoUtils.noop,
    polygonEnd: geoUtils.noop,
    sphere: geoUtils.noop
  }));
  ring.push(ring[0]);
  return ring;
}
​
​
geoUtils.dorling = function(d) {
  // From Jason Davis https://www.jasondavies.com/maps/dorling-world/
  switch (d.type) {
    case "Polygon": return geoUtils.circle(geoUtils.projectRing(d.coordinates[0]));
    case "MultiPolygon": return geoUtils.circle(geoUtils.projectRing(d.coordinates[0][0]));
  }
  return {radius: 0, coordinates: []};
}
​
​
geoUtils.circle = function(coordinates) {
  // From Mike Bostock’s https://bl.ocks.org/3081153
  var circle = [],
      length = 0,
      lengths = [length],
      polygon = d3.geom.polygon(coordinates),
      p0 = coordinates[0],
      p1,
      x,
      y,
      i = 0,
      n = coordinates.length - 1;
​
  // Compute the distances of each coordinate.
  while (++i < n) {
    p1 = coordinates[i];
    x = p1[0] - p0[0];
    y = p1[1] - p0[1];
    lengths.push(length += Math.sqrt(x * x + y * y));
    p0 = p1;
  }
​
  var area = polygon.area(),
      radius = Math.sqrt(Math.abs(area) / Math.PI),
      centroid = polygon.centroid(-1 / (6 * area)),
      angleOffset = Math.atan2(coordinates[0][1] - centroid[1], coordinates[0][0] - centroid[0]),
      angle,
      i = -1,
      k = 2 * Math.PI / length;
​
  // Compute points along the circle’s circumference at equivalent distances.
  while (++i < n) {
    angle = angleOffset + lengths[i] * k;
    circle.push([
      centroid[0] + radius * Math.cos(angle),
      centroid[1] + radius * Math.sin(angle)
    ]);
  }
​
  return {coordinates: circle, radius: radius, centroid: centroid};
}
​
​
geoUtils.polygons = function(geometries) {
  // From Jason Davis https://www.jasondavies.com/maps/dorling-world/
  var id = 0;
  return d3.merge(geometries.map(function(geometry) {
    var iso = isoCodesMap.get(geometry.id);
    var isoName = iso ? iso.alpha3 : "";
​
    return (geometry.type === "MultiPolygon" ? geometry.arcs : [geometry.arcs]).map(function(d) {
      reverseCountryMap[++id] = isoName;
      return {id: id, type: "Polygon", arcs: d, parent: geometry};
    });
  }));
}
​
​
geoUtils.collide = function(node) {
  // From https://mbostock.github.com/d3/talk/20111018/collision.html
  var r = node.radius,
      nx1 = node.x - r,
      nx2 = node.x + r,
      ny1 = node.y - r,
      ny2 = node.y + r;
  return function(quad, x1, y1, x2, y2) {
    if (quad.point && (quad.point !== node)) {
      var x = node.x - quad.point.x,
          y = node.y - quad.point.y,
          l = Math.sqrt(x * x + y * y),
          r = node.dorling.radius + quad.point.dorling.radius;
      if (l < r) {
        l = (l - r) / l * .5;
        node.x -= x *= l;
        node.y -= y *= l;
        quad.point.x += x;
        quad.point.y += y;
      }
    }
    return x1 > nx2
        || x2 < nx1
        || y1 > ny2
        || y2 < ny1;
  };
}
​
geoUtils.noop = function() {}
​
geoUtils.pathCircle = function(x, y, radius) {
  return "M" + x + "," + (y + radius)
      + "a" + radius + "," + radius + " 0 1,1 0," + -2 * radius
      + "a" + radius + "," + radius + " 0 1,1 0," + 2 * radius
      + "z";
}
​
​
geoUtils.projectionTween = function(projection0, projection1) {
  // by Mike Bostock
  return function(d) {
    var t = 0;
​
    var projection = d3.geo.projection(project)
        .scale(1)
        .translate([width / 2, height / 2]);
​
    var path = d3.geo.path()
        .projection(projection);
​
    function project(λ, φ) {
      λ *= 180 / Math.PI, φ *= 180 / Math.PI;
      var p0 = projection0([λ, φ]), p1 = projection1([λ, φ]);
      var x = (1 - t) * p0[0] + t * p1[0];
      var y = (1 - t) * -p0[1] + t * -p1[1];
​
      // hacky error workaround
      if(x == Infinity || x == -Infinity ) x = -height-1;
      if(y == Infinity || y == -Infinity) y = -height-1;
​
      if(isNaN(x)) x = -height;
      if(isNaN(y)) y = -height;
​
      return [x, y];
    }
​
    return function(_) {
      t = _;
      return d.geometry ? path(d.geometry) : path(d);
    };
  };
}
  </script>
</body>
</html>
​
    