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

<!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 src='./index.js' lang='babel' type='text/babel'>
</script>
</body>
</html>

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