pathg.selectAll("path").remove();

return "M" +
    d3.polygonHull(d.values.map(function(i) { return [i.x, i.y]; }))
    .join("L") + "Z";

var poly = d3.polygonHull(d.values.map(function(i) { return [i.x, i.y]; }));
if (poly){
 return "M" + poly.join("L") + "Z";
}