block by nbremer d2720fdaab1123df73f4806360a09c9e

Data based orientations in SVG Gradients - Step 1

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This Chord diagram shows the first step of the example used in my blog on Data-based orientations for gradients in a d3.js Chord Diagram

What you see here are movie collaborations between the Avengers in the MCU (up until & including Thor Ragnarok). This is how a normal chord diagram would look with the Avenger collaborations dataset. As you can see each chord is given only 1 color. But because collaborations are symmetrical, the chords are all as thick at the beginnen as at the end. Therefore, I wanted each chord to represent both the Avengers that it connects through a gradient. That is what will be addressed in the next two steps.

You can find the steps after this one here

script.js

////////////////////////////////////////////////////////////
//////////////////////// Set-Up ////////////////////////////
////////////////////////////////////////////////////////////

var margin = {left:90, top:90, right:90, bottom:90},
	width = Math.min(window.innerWidth, 700) - margin.left - margin.right,
    height = Math.min(window.innerWidth, 700) - margin.top - margin.bottom,
    innerRadius = Math.min(width, height) * .39,
    outerRadius = innerRadius * 1.1;
	
var Names = ["Black Widow","Captain America","Hawkeye","the Hulk","Iron Man","Thor"],
	colors = ["#301E1E", "#083E77", "#342350", "#567235", "#8B161C", "#DF7C00"],
	opacityDefault = 0.8;

var matrix = [
	[0,4,3,2,5,2], //Black Widow
	[4,0,3,2,4,3], //Captain America
	[3,3,0,2,3,3], //Hawkeye
	[2,2,2,0,3,3], //The Hulk
	[5,4,3,3,0,2], //Iron Man
	[2,3,3,3,2,0], //Thor
];

////////////////////////////////////////////////////////////
/////////// Create scale and layout functions //////////////
////////////////////////////////////////////////////////////

var colors = d3.scale.ordinal()
    .domain(d3.range(Names.length))
	.range(colors);

var chord = d3.layout.chord()
    .padding(.15)
    .sortChords(d3.descending)
	.matrix(matrix);
		
var arc = d3.svg.arc()
    .innerRadius(innerRadius*1.01)
    .outerRadius(outerRadius);

var path = d3.svg.chord()
	.radius(innerRadius);
	
////////////////////////////////////////////////////////////
////////////////////// Create SVG //////////////////////////
////////////////////////////////////////////////////////////
	
var svg = d3.select("#chart").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
	.append("g")
    .attr("transform", "translate(" + (width/2 + margin.left) + "," + (height/2 + margin.top) + ")");
		
////////////////////////////////////////////////////////////
////////////////// Draw outer Arcs /////////////////////////
////////////////////////////////////////////////////////////

var outerArcs = svg.selectAll("g.group")
	.data(chord.groups)
	.enter().append("g")
	.attr("class", "group")
	.on("mouseover", fade(.1))
	.on("mouseout", fade(opacityDefault));

outerArcs.append("path")
	.style("fill", function(d) { return colors(d.index); })
	.attr("d", arc);
	
////////////////////////////////////////////////////////////
////////////////////// Append Names ////////////////////////
////////////////////////////////////////////////////////////

//Append the label names on the outside
outerArcs.append("text")
  .each(function(d) { d.angle = (d.startAngle + d.endAngle) / 2; })
  .attr("dy", ".35em")
  .attr("class", "titles")
  .attr("text-anchor", function(d) { return d.angle > Math.PI ? "end" : null; })
  .attr("transform", function(d) {
		return "rotate(" + (d.angle * 180 / Math.PI - 90) + ")"
		+ "translate(" + (outerRadius + 10) + ")"
		+ (d.angle > Math.PI ? "rotate(180)" : "");
  })
  .text(function(d,i) { return Names[i]; });
	
////////////////////////////////////////////////////////////
////////////////// Draw inner chords ///////////////////////
////////////////////////////////////////////////////////////
  
svg.selectAll("path.chord")
	.data(chord.chords)
	.enter().append("path")
	.attr("class", "chord")
	.style("fill", function(d) { return colors(d.source.index); })
	.style("opacity", opacityDefault)
	.attr("d", path);

////////////////////////////////////////////////////////////
////////////////// Extra Functions /////////////////////////
////////////////////////////////////////////////////////////

//Returns an event handler for fading a given chord group.
function fade(opacity) {
  return function(d,i) {
    svg.selectAll("path.chord")
        .filter(function(d) { return d.source.index != i && d.target.index != i; })
		.transition()
        .style("opacity", opacity);
  };
}//fade

index.html

<!DOCTYPE html>
<html>
	<head>
		<meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
		<title>Step 1 - Collaborations between MCU Avengers</title>
	
		<!-- D3.js -->
		<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js" charset="utf-8"></script>
		
		<!-- Google Fonts -->
		<link href='https://fonts.googleapis.com/css?family=Lato:400,900' rel='stylesheet' type='text/css'>
		
		<style>
			body {
			  font-size: 12px;
			  font-family: 'Lato', sans-serif;
			  text-align: center;
			  fill: #2B2B2B;
			  cursor: default;
			}
			
			@media (min-width: 600px) {
				#chart{
					font-size: 16px;
				}
			}
		</style>
	</head>
	<body>
	
		<div id = "chart"></div>
		<script src = "script.js"></script>

  </body>
</html>