world map 09 ckmeans cluster min breaks

in this iteration, we use the ckmeans algorithm from the simple-statistics package to cluster our data. we pick the minimum value of each cluster as a break. we then use these breaks with a quantile scale to map values in the data to colors on the choropleth map.

this is method is my current favorite way to create breaks, or color thresholds, for a choropleth map.

🎩 @Elijah_Meeks for the idea to try the ckmeans algorithm, as it seems to be the new hotness in the choropleth map breaks scene

a further 🙏 to @recifs for talking through where in the ckmeans clusters its reasonable to pick breaks from.
tl;dr any number between max(class n) and min(class n+1) is OK

do check out the other examples in this world map series:

world map 00 original example
world map 01 fix tooltip value
world map 02 d3 v4
world map 03 es2015 + update code style
world map 04 manual breaks + threshold scale
world map 05 linear breaks + quantize scale
world map 06 linear breaks + quantiles scale
world map 07 Jenks natural breaks
world map 08 ckmeans cluster max breaks
world map 09 ckmeans cluster min breaks

forked from micahstubbs's block: world map 09 ckmeans cluster min breaks

<!DOCTYPE html>
<meta charset="utf-8">
<style>
  .names {
    fill: none;
    stroke: #fff;
    stroke-linejoin: round;
  }
  
  /* Tooltip CSS */
  .d3-tip {
    line-height: 1.5;
    font-weight: 400;
    font-family:"avenir next", Arial, sans-serif;
    padding: 6px;
    background: rgba(0, 0, 0, 0.6);
    color: #FFA500;
    border-radius: 1px;
    pointer-events: none;
  }

/* Creates a small triangle extender for the tooltip */
  .d3-tip:after {      
    box-sizing: border-box;
    display: inline;
    font-size: 8px;
    width: 100%;
    line-height: 1.5;
    color: rgba(0, 0, 0, 0.6);
    position: absolute;
    pointer-events: none;
    
  }

/* Northward tooltips */
  .d3-tip.n:after {
    content: "\25BC";
    margin: -1px 0 0 0;
    top: 100%;
    left: 0;
    text-align: center;
  }

/* Eastward tooltips */
  .d3-tip.e:after {
    content: "\25C0";
    margin: -4px 0 0 0;
    top: 50%;
    left: -8px;
  }

/* Southward tooltips */
  .d3-tip.s:after {
    content: "\25B2";
    margin: 0 0 1px 0;
    top: -8px;
    left: 0;
    text-align: center;
  }

/* Westward tooltips */
  .d3-tip.w:after {
    content: "\25B6";
    margin: -4px 0 0 -1px;
    top: 50%;
    left: 100%;
  }

/*    
  text{
    pointer-events:none;
  }
  */

.details{
    color: white;
  }
</style>
<body>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script src="https://d3js.org/queue.v1.min.js"></script>
<script src="https://d3js.org/topojson.v1.min.js"></script>
<script src="https://d3js.org/d3-geo-projection.v1.min.js"></script>
<script src="d3-tip.js"></script>
<script src='https://unpkg.com/simple-statistics@2.0.0/dist/simple-statistics.min.js'></script>
<script src='https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.10.3/babel.min.js'></script>
<script lang='babel' type='text/babel'>
// configuration
const colorVariable = 'population';
const geoIDVariable = 'id';
const format = d3.format(',');

// Set tooltips
const tip = d3.tip()
  .attr('class', 'd3-tip')
  .offset([-10, 0])
  .html(d => `<strong>Country: </strong><span class='details'>${d.properties.name}<br></span><strong>Concentration: </strong><span class='details'>${format(d[colorVariable])}</span>`);

tip.direction(function(d) {
  if (d.properties.name === 'Antarctica') return 'n';
  // Americas
  if (d.properties.name === 'Greenland') return 's';
  if (d.properties.name === 'Canada') return 'e';
  if (d.properties.name === 'USA') return 'e';
  if (d.properties.name === 'Mexico') return 'e';
  // Europe
  if (d.properties.name === 'Iceland') return 's';
  if (d.properties.name === 'Norway') return 's';
  if (d.properties.name === 'Sweden') return 's';
  if (d.properties.name === 'Finland') return 's';
  if (d.properties.name === 'Russia') return 'w';
  // Asia
  if (d.properties.name === 'China') return 'w';
  if (d.properties.name === 'Japan') return 's';
  // Oceania
  if (d.properties.name === 'Indonesia') return 'w';
  if (d.properties.name === 'Papua New Guinea') return 'w';
  if (d.properties.name === 'Australia') return 'w';
  if (d.properties.name === 'New Zealand') return 'w';
  // otherwise if not specified
  return 'n';
})

tip.offset(function(d) { // [top, left]
  if (d.properties.name === 'Antarctica') return [0, 0];
  // Americas
  if (d.properties.name === 'Greenland') return [10, -10];
  if (d.properties.name === 'Canada') return [24, -28];
  if (d.properties.name === 'USA') return [-5, 8];
  if (d.properties.name === 'Mexico') return [12, 10];
  if (d.properties.name === 'Chile') return [0, -15];
  // Europe
  if (d.properties.name === 'Iceland') return [15, 0];
  if (d.properties.name === 'Norway') return [10, -28];
  if (d.properties.name === 'Sweden') return [10, -8];
  if (d.properties.name === 'Finland') return [10, 0];
  if (d.properties.name === 'France') return [-9, 66];
  if (d.properties.name === 'Italy') return [-8, -6];
  if (d.properties.name === 'Russia') return [5, 385];
  // Africa
  if (d.properties.name === 'Madagascar') return [-10, 10];
  // Asia
  if (d.properties.name === 'China') return [-16, -8];
  if (d.properties.name === 'Mongolia') return [-5, 0];
  if (d.properties.name === 'Pakistan') return [-10, 13];
  if (d.properties.name === 'India') return [-11, -18];
  if (d.properties.name === 'Nepal') return [-8, 1];
  if (d.properties.name === 'Myanmar') return [-12, 0];
  if (d.properties.name === 'Laos') return [-12, -8];
  if (d.properties.name === 'Vietnam') return [-12, -4];
  if (d.properties.name === 'Japan') return [5, 5];
  // Oceania
  if (d.properties.name === 'Indonesia') return [0, -5];
  if (d.properties.name === 'Papua New Guinea') return [-5, -10];
  if (d.properties.name === 'Australia') return [-15, 0];
  if (d.properties.name === 'New Zealand') return [-15, 0];
  // otherwise if not specified
  return [-10, 0];
})

d3.select('body')
    .style('overflow', 'hidden');

const parentWidth = d3.select('body').node().getBoundingClientRect().width;
const margin = {top: 0, right: 0, bottom: 0, left: 0};
const width = 960 - margin.left - margin.right;
const height = 500 - margin.top - margin.bottom;

const color = d3.scaleQuantile()
  .range([
    'rgb(247,251,255)',
    'rgb(222,235,247)', 
    'rgb(198,219,239)', 
    'rgb(158,202,225)',
    'rgb(107,174,214)',
    'rgb(66,146,198)',
    'rgb(33,113,181)',
    'rgb(8,81,156)',
    'rgb(8,48,107)',
    'rgb(3,19,43)'
  ]);

const svg = d3.select('body')
  .append('svg')
  .attr('width', width)
  .attr('height', height)
  .append('g')
  .attr('class', 'map');

const projection = d3.geoRobinson()
  .scale(148)
  .rotate([352, 0, 0])
  .translate( [width / 2, height / 2]);

const path = d3.geoPath().projection(projection);

svg.call(tip);

queue()
  .defer(d3.json, 'world_countries.json')
  .defer(d3.tsv, 'world_population.tsv')
  .await(ready);

function ready(error, geography, data) {
  data.forEach(d => {
    d[colorVariable] = Number(d[colorVariable].replace(',', ''));
  })

const colorVariableValueByID = {};

data.forEach(d => { colorVariableValueByID[d[geoIDVariable]] = d[colorVariable]; });
  geography.features.forEach(d => { d[colorVariable] = colorVariableValueByID[d.id] });

// calculate ckmeans clusters
  // then use the max value of each cluster
  // as a break
  const numberOfClasses = color.range().length - 1;
  const ckmeansClusters = ss.ckmeans(data.map(d => d[colorVariable]), numberOfClasses);
  const ckmeansBreaks = ckmeansClusters.map(d => d3.min(d));
  console.log('numberOfClasses', numberOfClasses);
  console.log('ckmeansClusters', ckmeansClusters);
  console.log('ckmeansBreaks', ckmeansBreaks);

// set the domain of the color scale based on our data
  color
  //  .domain(ckmeansBreaks);
  //
  // .domain(jenksNaturalBreaks)
  //
  // .domain(d3.extent(data, d => d[colorVariable]));
  //
  .domain([
    0,
    5,
    10,
    20,
    30,
    40,
    50,
    60,
    70,
    80,
    90,
  ]);

svg.append('g')
    .attr('class', 'countries')
    .selectAll('path')
    .data(geography.features)
    .enter().append('path')
      .attr('d', path)
      .style('fill', d => {
        if (typeof colorVariableValueByID[d.id] !== 'undefined') {
          return color(colorVariableValueByID[d.id])
        } 
        return 'white'
      })
      .style('fill-opacity',0.8)
      .style('stroke', d => {
          if (d[colorVariable] !== 0) {
          return 'white';
        } 
        return 'lightgray';
      })
      .style('stroke-width', 1)
      .style('stroke-opacity', 0.5)
      // tooltips
      .on('mouseover',function(d){
        tip.show(d);
        d3.select(this)
          .style('fill-opacity', 1)
          .style('stroke-opacity', 1)
          .style('stroke-width', 2)
      })
      .on('mouseout', function(d){
        tip.hide(d);
        d3.select(this)
          .style('fill-opacity', 0.8)
          .style('stroke-opacity', 0.5)
          .style('stroke-width', 1)
      });

svg.append('path')
    .datum(topojson.mesh(geography.features, (a, b) => a.id !== b.id))
    .attr('class', 'names')
    .attr('d', path);
}
</script>
</body>
</html>

Modified http://d3js.org/d3.v4.min.js to a secure url

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

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

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

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

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

https://d3js.org/d3-geo-projection.v1.min.js

https://unpkg.com/simple-statistics@2.0.0/dist/simple-statistics.min.js

https://cdnjs.cloudflare.com/ajax/libs/babel-standalone/6.10.3/babel.min.js