project

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <script src="https://d3js.org/topojson.v2.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    // Feel free to change or delete any of the code you see in this editor!
    /*var svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)

svg.append("text")
      .text("Edit the code below to change me!")
      .attr("y", 200)
      .attr("x", 120)
      .attr("font-size", 36)
      .attr("font-family", "monospace")*/

d3.json("Allegheny_County_Census_Tracts_2016.geojson", function(json){
      // Loop through each state data value in the .csv file
    for (var i = 0; i < data.length; i++) {

// Grab census tract
      var dataState = data[i].censusTract;

// Grab data value 
      var dataValue = data[i].value;

// Find the corresponding state inside the GeoJSON
      for (var j = 0; j < json.features.length; j++) {
        var jsonState = json.features[j].properties.name;

if (dataState == jsonState) {

// Copy the data value into the JSON
          json.features[j].properties.value = dataValue;

// Stop looking through the JSON
          break;
        }
      }
    }
    })
   // d3.queue()
     //   .defer(d3.json, "Allegheny_County_Census_Tracts_2016.geojson")
    
  </script>
</body>

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https://d3js.org/topojson.v2.min.js