Pie Chart Rotation on Click

This pie chart, based on Mike Bostock's example, rotates so that any clicked wedge well spin to the bottom. The text rotates in the opposite direction so that it remains upright.

Part of this answer on Stack Overflow

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

.arc text {
  font: 10px sans-serif;
  text-anchor: middle;
}

.arc path {
  stroke: #fff;

</style>
<svg width="960" height="600"></svg>
<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
var svg = d3.select("svg"),
    width = +svg.attr("width"),
    height = +svg.attr("height"),
    radius = Math.min(width, height) / 2,
    g = svg.append("g").attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");

var color = d3.scaleOrdinal(["#98abc5", "#8a89a6", "#7b6888", "#6b486b", "#a05d56", "#d0743c", "#ff8c00"]);

var data = [ {age:"<5", population: 2704659},{age:"5-13", population: 4499890},{age:"14-17", population: 2159981},{age:"18-24", population: 3853788},{age:"25-44", population: 14106543},{age:"45-64", population: 8819342},{age:"≥65", population: 612463} ]

var pie = d3.pie()
    .sort(null)
    .value(function(d) { return d.population; });

var path = d3.arc()
    .outerRadius(radius - 10)
    .innerRadius(0);

var label = d3.arc()
    .outerRadius(radius - 40)
    .innerRadius(radius - 40);

var arc = g.selectAll(".arc")
    .data(pie(data))
    .enter().append("g")
      .attr("class", "arc");

arc.append("path")
    .attr("d", path)
    .attr("fill", function(d) { return color(d.data.age); })
    .on("click",function(d) { 
      // The amount we need to rotate:
      var rotate = 180-(d.startAngle + d.endAngle)/2 / Math.PI * 180;
    
      // Transition the pie chart
      g.transition()
        .attr("transform",  "translate(" + width / 2 + "," + height / 2 + ") rotate(" + rotate + ")")
        .duration(1000);
     
     // Τransition the labels:
     text.transition()
       .attr("transform", function(dd) {
         return "translate(" + label.centroid(dd) + ") rotate(" + (-rotate) + ")"; })
       .duration(1000);

});

var text = arc.append("text")
      .attr("transform", function(d) { return "translate(" + label.centroid(d) + ")"; })
      .attr("dy", "0.35em")
      .text(function(d) { return d.data.age; });

</script>

https://d3js.org/d3.v4.min.js