Simple filled area in v4

This is a simple graph demonstrating the addition of a filled area in conjunction with a line graph. This was written using d3.js v4 and is a follow on to the simple graph example here.

This graph is part of the code samples for the update to the book D3 Tips and Tricks to version 4 of d3.js.

forked from d3noob's block: Simple filled area in v4

<!DOCTYPE html>
<meta charset="utf-8">
<style> /* set the CSS */

.line {
  fill: none;
  stroke: rgba(0,128,255,0.5);
  stroke-width: 2px;
}

.area {
  fill: rgba(0,128,255,0.2);
}
  
.chart:hover .line {
  stroke: rgba(0,128,255,1);
}

</style>
<body>

<script src="https://d3js.org/d3.v4.min.js"></script>
<script>
console.clear();
// set the dimensions and margins of the graph
var margin = {top: 20, right: 20, bottom: 30, left: 50},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

// set the ranges
var x = d3.scaleLinear().range([0, width]);
var y = d3.scaleLinear().range([height, 0]);

// define the area
var area = d3.area()
    .x(function(d,i) { return x(d.x0); })
    .y0(height)
    .y1(function(d) { return y(d.length); });

// define the line
var valueline = d3.line()
    .x(function(d) { return x(d.x0); })
    .y(function(d) { return y(d.length); });

// append the svg obgect to the body of the page
// appends a 'group' element to 'svg'
// moves the 'group' element to the top left margin
var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
		.attr('class','chart')
  .append("g")
    .attr("transform",
          "translate(" + margin.left + "," + margin.top + ")");

render();
  
function render() {
  // generate data
  var data = d3.range(2000).map(d3.randomBates(6));
  var bins=d3.histogram().thresholds(x.ticks(200))(data);

// scale the range of the data
  x.domain(d3.extent(bins, function(d,i) { return d.x0; })).nice(2);
  y.domain(d3.extent(bins, function(d) { return d.length; })).nice();

// add the area
  var a = svg.selectAll('.area')
     .data([bins]); // must cast as array
  
  var l = svg.selectAll('.line')
    .data([bins]);
  
  // enter
  a.enter()
    .append("path")
    .attr("class", "area")
    .transition()
    .duration(250)
    .attr("d", area);
 
  // update
  a.transition()
    .duration(250)
  	.attr("d", area);
    
  // exit
  a.exit().remove();
  
  // enter
  l.enter()
    .append("path")
    .attr("class", "line")
    .transition()
    .duration(250)
    .attr("d", valueline);
 
  // update
  l.transition()
    .duration(250)
  	.attr("d", valueline);
    
  // exit
  l.exit().remove();
  
  // add the X Axis
	var axisx = svg.append("g")
    .attr("transform", "translate(0," + height + ")")
    .call(d3.axisBottom(x));

// add the Y Axis
	svg.append("g")
    .call(d3.axisLeft(y));

}

svg.on('click', function(){
  render();
});

</script>
</body>

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