.block

## .block
license: gpl-3.0

## README.md

      
          Raw
        
        
              README.md
            
          
    Working with spatial data

Example #16

Using turf.js to measure features

forked from mbostock's block: U.S. Counties TopoJSON

forked from enjalot's block: WWSD #12: d3 + TopoJSON

forked from enjalot's block: WWSD #13: d3 + Canvas

  
## index.html
<!DOCTYPE html>
<meta charset="utf-8">
<style>

path {
  fill: #ccc;
  stroke: #fff;
  stroke-width: .5px;
}

path:hover {
  fill: red;
}

</style>
<body>
  <canvas></canvas>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Turf.js/2.0.2/turf.min.js"></script>
<script>

var width = 960,
    height = 500;

var canvas = d3.select("canvas").node()
canvas.width = width;
canvas.height = height;
var ctx = canvas.getContext('2d')

var projection = d3.geo.mercator()
.center([-122.2615006,37.8469266])
.scale(2000)

var path = d3.geo.path()
  .projection(projection)
  .context(ctx)


var url = "http://enjalot.github.io/wwsd/data/USA/california-streams.topojson"
d3.json(url, function(error, topology) {
  if (error) throw error;

  console.log("topojson", topology)
  var geojson = topojson.feature(topology, topology.objects['us-streams-unmerged-18']);
  console.log("geojson", geojson)

  var maxLength = d3.max(geojson.features, function(d) {
    var length = turf.lineDistance(d, 'miles');
    d.properties.length = length;
    return length;
  })

  var color = d3.scale.threshold()
  .domain([0, 2, 20, maxLength])
  .range(["#853c3c", "#85763c", "#3c8544", "#0068b7"])

  ctx.strokeStyle = "#111";
  ctx.fillStyle = "#99ffe8"
  geojson.features.forEach(function(feature) {
    ctx.strokeStyle = color(feature.properties.length)
    ctx.beginPath()
    path(feature)
    ctx.stroke();
  })
});

</script>

## thumbnail.png

      
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              thumbnail.png