.block

## .block
license: gpl-3.0

## README.md

      
        

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              README.md
            
          
        
      
    
  
    This symbol map encodes the area of each county using a circle at the county's centroid.

  

  

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

circle {
  fill: none;
  stroke: steelblue;
}

</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script src="//d3js.org/topojson.v1.min.js"></script>
<script>

var width = 960,
    height = 500;

var path = d3.geo.path();

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

d3.json("/mbostock/raw/4090846/us.json", function(error, us) {
  if (error) throw error;

  svg.selectAll("circle")
      .data(topojson.feature(us, us.objects.counties).features)
    .enter().append("circle")
      .attr("transform", function(d) { return "translate(" + path.centroid(d) + ")"; })
      .attr("r", function(d) { return Math.sqrt(path.area(d) / Math.PI); });
});

</script>

## thumbnail.png

      
        

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              thumbnail.png