Pie Centroid

The black dots show the midpoint computed by d3-shape’s arc.centroid. Note that this is not the geometric center of the arc, which may be outside the arc; this method is merely a convenience for positioning labels.

forked from mbostock's block: Pie Centroid

forked from anonymous's block: Pie Centroid

<!DOCTYPE html>
<meta charset="utf-8">
<canvas width="960" height="500"></canvas>
<script src="//d3js.org/d3.v4.0.0-alpha.4.min.js"></script>
<script>

var data = [];
var i;
for(var i=0; i< 5; i++)
        	{
        		data.push(Math.floor(Math.random() * 100 +20 ));
       	}

var canvas = document.querySelector("canvas"),
    context = canvas.getContext("2d");

var width = canvas.width,
    height = canvas.height,
    radius = Math.min(width, height) / 2;

var arc = d3.arc()
    .outerRadius(radius - 10)
    .innerRadius(100)
    .context(context);

var dot = d3.symbol()
    .context(context);

var pie = d3.pie();

var arcs = pie(data);

context.translate(width / 2, height / 2);

arcs.forEach(function(d, i) {
  context.beginPath();
  arc(d);
  context.fillStyle = 'white';
  context.fill();
});

context.beginPath();
arcs.forEach(arc);
context.lineWidth = 1.5;
context.stroke();

context.beginPath();

function num(){
  var num1=Math.floor(Math.random()*5);
  var num2=Math.floor(Math.random()*5);
  while(num1>=num2){
    num1=Math.floor(Math.random()*5)
  }
  return [num1,num2];
}
var index=num()

arcs.forEach(function(d) {
  var c = arc.centroid(d);
  context.save();
  context.translate(c[0], c[1]);
  dot();
  context.restore();
});
context.fillStyle = "#000";
context.fill();

</script>

https://d3js.org/d3.v4.0.0-alpha.4.min.js