Convex Hull

This example uses d3.geom.hull to compute the 2D convex hull of a set of points. An outer stroke is used to pad the hull. Click to add a new point.

forked from mbostock's block: Convex Hull

<!DOCTYPE html>
<meta charset="utf-8">
<title>Convex Hull</title>
<style>

rect {
  fill: none;
  pointer-events: all;
}

.hull {
  fill: steelblue;
  stroke: steelblue;
  stroke-width: 32px;
  stroke-linejoin: round;
}

circle {
  fill: white;
  stroke: black;
  stroke-width: 1.5px;
}

</style>
<body>
<button id="changeBtn">Change</button>	
<script src="//d3js.org/d3.v3.min.js"></script>
<script>

var width = 500,
    height = 500;

var randomX = d3.random.normal(width / 2, 60),
    randomY = d3.random.normal(height / 2, 60);

function generatePoints(count){
	return d3.range(count).map(function() { 
    return [randomX(), randomY()]; 
  });  
}
  
var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height)

svg.append("rect")
    .attr("width", width)
    .attr("height", height);

var hull = svg.append("path")
  .attr("class", "hull");

draw(generatePoints(10));

function draw(points) {
  hull.datum(d3.geom.hull(points))
  	.transition()
    .attr("d", function(d) { 
    	return "M" + d.join("L") + "Z"; 
  	});

var selection = svg.selectAll("circle")
  	.data(points);
  selection.enter()
    .append("circle")
    .attr("r", 3);
  selection.transition()
    .attr("transform", function(d) { 
    	return "translate(" + d + ")"; 
  	});
  selection.exit().remove();
}
  
document.getElementById('changeBtn').addEventListener('click', function(){
  draw(generatePoints(Math.round(3 + Math.random()*6)));
})

</script>

https://d3js.org/d3.v3.min.js