text: function find_largest(d) {
    var areas = [];
    var threshold = 0.9;
    d.geometry.coordinates = d.geometry.coordinates.filter(function(c, i) {
      var test = copy(d);
      test.geometry.coordinates = [test.geometry.coordinates[i]];
      var a = path.area(test);
      if (a >= threshold) {
        areas.push(a);
        return true;
      }
      return false;
    });
    areas.sort(function(a,b) { return a-b; });
  
    var reduced = copy(d),
        largest = copy(d);
    reduced.geometry.coordinates = reduced.geometry.coordinates.filter(function(c, i) {
      var test = copy(d);
      test.geometry.coordinates = [test.geometry.coordinates[i]];
      var a = path.area(test);
      if (a == areas[areas.length-1]) {
        largest.geometry.coordinates = test.geometry.coordinates;
      }
      return a >= d3.quantile(areas, .9);
    });
  
    var coords = largest.geometry.coordinates[0];
  
    if (coords && largest.geometry.type === "MultiPolygon") {
      coords = coords[0];
      largest.geometry.coordinates[0] = coords;
      largest.geometry.type = "Polygon";
    }
    return largest;
  }
  
  function copy(source) {
    return JSON.parse(JSON.stringify(source));
  }
  