gistfile1.js

vertices = [];
for (i=0; i<turnoutData.length; i++) {
  vertices.push([x(turnoutData[i].date), y(turnoutData[i].registered_voters_percent)])
}
svg.selectAll("path.cell")
      .data(d3.geom.voronoi(vertices))
    .enter().append("path")
      .attr({
        "class": "cell",
        d: function(d, i) {
              return "M" + d.join("L") + "Z";
        }
      });