Stretched Chord - The Final Result

.block

height: 660

README.md

Final step (number 6) from my blog on How to create a Flow diagram with a circular Twist in which the Chord Diagram is now officially a circular flow diagram and the chords have been sorted to reduce overlap. An example based on actual data can be found here

d3.layout.chord.sort.js

customChordLayout = function() {
	var ε = 1e-6, ε2 = ε * ε, π = Math.PI, τ = 2 * π, τε = τ - ε, halfπ = π / 2, d3_radians = π / 180, d3_degrees = 180 / π;
    var chord = {}, chords, groups, matrix, n, padding = 0, sortGroups, sortSubgroups, sortChords;
    function relayout() {
      var subgroups = {}, groupSums = [], groupIndex = d3.range(n), subgroupIndex = [], k, x, x0, i, j;
      chords = [];
      groups = [];
      k = 0, i = -1;
      while (++i < n) {
        x = 0, j = -1;
        while (++j < n) {
          x += matrix[i][j];
        }
        groupSums.push(x);
        subgroupIndex.push(d3.range(n).reverse());
        k += x;
      }
      if (sortGroups) {
        groupIndex.sort(function(a, b) {
          return sortGroups(groupSums[a], groupSums[b]);
        });
      }
      if (sortSubgroups) {
        subgroupIndex.forEach(function(d, i) {
          d.sort(function(a, b) {
            return sortSubgroups(matrix[i][a], matrix[i][b]);
          });
        });
      }
      k = (τ - padding * n) / k;
      x = 0, i = -1;
      while (++i < n) {
        x0 = x, j = -1;
        while (++j < n) {
          var di = groupIndex[i], dj = subgroupIndex[di][j], v = matrix[di][dj], a0 = x, a1 = x += v * k;
          subgroups[di + "-" + dj] = {
            index: di,
            subindex: dj,
            startAngle: a0,
            endAngle: a1,
            value: v
          };
        }
        groups[di] = {
          index: di,
          startAngle: x0,
          endAngle: x,
          value: (x - x0) / k
        };
        x += padding;
      }
      i = -1;
      while (++i < n) {
        j = i - 1;
        while (++j < n) {
          var source = subgroups[i + "-" + j], target = subgroups[j + "-" + i];
          if (source.value || target.value) {
            chords.push(source.value < target.value ? {
              source: target,
              target: source
            } : {
              source: source,
              target: target
            });
          }
        }
      }
      if (sortChords) resort();
    }
    function resort() {
      chords.sort(function(a, b) {
        return sortChords((a.source.value + a.target.value) / 2, (b.source.value + b.target.value) / 2);
      });
    }
    chord.matrix = function(x) {
      if (!arguments.length) return matrix;
      n = (matrix = x) && matrix.length;
      chords = groups = null;
      return chord;
    };
    chord.padding = function(x) {
      if (!arguments.length) return padding;
      padding = x;
      chords = groups = null;
      return chord;
    };
    chord.sortGroups = function(x) {
      if (!arguments.length) return sortGroups;
      sortGroups = x;
      chords = groups = null;
      return chord;
    };
    chord.sortSubgroups = function(x) {
      if (!arguments.length) return sortSubgroups;
      sortSubgroups = x;
      chords = null;
      return chord;
    };
    chord.sortChords = function(x) {
      if (!arguments.length) return sortChords;
      sortChords = x;
      if (chords) resort();
      return chord;
    };
    chord.chords = function() {
      if (!chords) relayout();
      return chords;
    };
    chord.groups = function() {
      if (!groups) relayout();
      return groups;
    };
    return chord;
  };

d3.stretched.chord.js

////////////////////////////////////////////////////////////
/////////////// Custom Chord Function //////////////////////
//////// Pulls the chords pullOutSize pixels apart /////////
////////////////// along the x axis ////////////////////////
////////////////////////////////////////////////////////////
///////////// Created by Nadieh Bremer /////////////////////
//////////////// VisualCinnamon.com ////////////////////////
////////////////////////////////////////////////////////////
//// Adjusted from the original d3.svg.chord() function ////
///////////////// from the d3.js library ///////////////////
//////////////// Created by Mike Bostock ///////////////////
////////////////////////////////////////////////////////////

stretchedChord = function() {
    var source = d3_source, 
    target = d3_target, 
    radius = d3_svg_chordRadius, 
    startAngle = d3_svg_arcStartAngle, 
    endAngle = d3_svg_arcEndAngle,
    pullOutSize = 0;
    
  var π = Math.PI,
    halfπ = π / 2;

    function subgroup(self, f, d, i) {
    var subgroup = f.call(self, d, i), 
      r = radius.call(self, subgroup, i), 
      a0 = startAngle.call(self, subgroup, i) - halfπ, 
      a1 = endAngle.call(self, subgroup, i) - halfπ;
      return {
        r: r,
        a0: [a0],
        a1: [a1],
        p0: [ r * Math.cos(a0), r * Math.sin(a0)],
        p1: [ r * Math.cos(a1), r * Math.sin(a1)]
      };
    }

    function arc(r, p, a) {
    var sign = (p[0] >= 0 ? 1 : -1);
    return "A" + r + "," + r + " 0 " + +(a > π) + ",1 " + (p[0] + sign*pullOutSize) + "," + p[1];
    }


    function curve(p1) {
    var sign = (p1[0] >= 0 ? 1 : -1);
    return "Q 0,0 " + (p1[0] + sign*pullOutSize) + "," + p1[1];
    }
  
  /*
  M = moveto
  M x,y
  Q = quadratic Bézier curve
  Q control-point-x,control-point-y end-point-x, end-point-y
  A = elliptical Arc
  A rx, ry x-axis-rotation large-arc-flag, sweep-flag  end-point-x, end-point-y
  Z = closepath

  M251.5579641956022,87.98204731514328
  A266.5,266.5 0 0,1 244.49937503334525,106.02973926358392
  Q 0,0 -177.8355222451483,198.48621369706098
  A266.5,266.5 0 0,1 -191.78901944612068,185.0384338992728
  Q 0,0 251.5579641956022,87.98204731514328
  Z
  */  
    function chord(d, i) {
    var s = subgroup(this, source, d, i), 
      t = subgroup(this, target, d, i);
          
  return "M" + (s.p0[0] + pullOutSize) + "," + s.p0[1] + 
      arc(s.r, s.p1, s.a1 - s.a0) + 
      curve(t.p0) + 
      arc(t.r, t.p1, t.a1 - t.a0) + 
      curve(s.p0) + 
      "Z";
   }//chord

    chord.radius = function(v) {
      if (!arguments.length) return radius;
      radius = d3_functor(v);
      return chord;
    };
    chord.pullOutSize = function(v) {
      if (!arguments.length) return pullOutSize;
      pullOutSize = v;
      return chord;
    };
    chord.source = function(v) {
      if (!arguments.length) return source;
      source = d3_functor(v);
      return chord;
    };
    chord.target = function(v) {
      if (!arguments.length) return target;
      target = d3_functor(v);
      return chord;
    };
    chord.startAngle = function(v) {
      if (!arguments.length) return startAngle;
      startAngle = d3_functor(v);
      return chord;
    };
    chord.endAngle = function(v) {
      if (!arguments.length) return endAngle;
      endAngle = d3_functor(v);
      return chord;
    };


  function d3_svg_chordRadius(d) {
      return d.radius;
  }

  function d3_source(d) {
    return d.source;
  }
    
  function d3_target(d) {
      return d.target;
  }

  function d3_svg_arcStartAngle(d) {
      return d.startAngle;
  }
    
  function d3_svg_arcEndAngle(d) {
      return d.endAngle;
  }

  function d3_functor(v) {
    return typeof v === "function" ? v : function() {
      return v;
    };
  }

  return chord;

}//stretchedChord

index.html

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
	<title>Stretched Chord to show Flows</title>

	<!-- D3.js -->	
    <script src="http://d3js.org/d3.v3.js"></script>
	<script src="d3.stretched.chord.js"></script>
	<script src="d3.layout.chord.sort.js"></script>
	
	<!-- jQuery -->
	<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
	
	<!-- Open Sans & CSS -->
	<link href='http://fonts.googleapis.com/css?family=Open+Sans:700,400,300' rel='stylesheet' type='text/css'>
	  <style>
		body {
		  font-family: 'Open Sans', sans-serif;
		  font-size: 12px;
		  font-weight: 400;
		  color: #525252;
		  text-align: center;
		}	
		
		line {
		  stroke: #000;
		  stroke-width: 1.px;
		}

		text {
		  font-size: 8px;
		}

		.titles{
		  font-size: 10px;
		}

		path.chord {
		  fill-opacity: .80;
		}
	  </style>
  </head>
  <body>

    <div id="chart"></div>	
    <script src="script.js"></script>
	
  </body>
</html>

script.js

////////////////////////////////////////////////////////////
//////////////////////// Set-up ////////////////////////////
////////////////////////////////////////////////////////////
var screenWidth = $(window).width(),
	mobileScreen = (screenWidth > 400 ? false : true);

var margin = {left: 50, top: 10, right: 50, bottom: 10},
	width = Math.min(screenWidth, 800) - margin.left - margin.right,
	height = (mobileScreen ? 300 : Math.min(screenWidth, 800)*5/6) - margin.top - margin.bottom;
			
var svg = d3.select("#chart").append("svg")
			.attr("width", (width + margin.left + margin.right))
			.attr("height", (height + margin.top + margin.bottom));
			
var wrapper = svg.append("g").attr("class", "chordWrapper")
			.attr("transform", "translate(" + (width / 2 + margin.left) + "," + (height / 2 + margin.top) + ")");;
			
var outerRadius = Math.min(width, height) / 2  - (mobileScreen ? 80 : 100),
	innerRadius = outerRadius * 0.95,
	pullOutSize = (mobileScreen? 20 : 50),
	opacityDefault = 0.7, //default opacity of chords
	opacityLow = 0.02; //hover opacity of those chords not hovered over
	
////////////////////////////////////////////////////////////
////////////////////////// Data ////////////////////////////
////////////////////////////////////////////////////////////

var Names = ["X","Y","Z","","C","B","A",""];

var respondents = 95, //Total number of respondents (i.e. the number that makes up the total group)
	emptyPerc = 0.4, //What % of the circle should become empty
	emptyStroke = Math.round(respondents*emptyPerc); 
var matrix = [
	[0,0,0,0,10,5,15,0], //X
	[0,0,0,0,5,15,20,0], //Y
	[0,0,0,0,15,5,5,0], //Z
	[0,0,0,0,0,0,0,emptyStroke], //Dummy stroke
	[10,5,15,0,0,0,0,0], //C
	[5,15,5,0,0,0,0,0], //B
	[15,20,5,0,0,0,0,0], //A
	[0,0,0,emptyStroke,0,0,0,0] //Dummy stroke
];
//Calculate how far the Chord Diagram needs to be rotated clockwise to make the dummy
//invisible chord center vertically
var offset = (2 * Math.PI) * (emptyStroke/(respondents + emptyStroke))/4;

//Custom sort function of the chords to keep them in the original order
function customSort(a,b) {
	return 1;
};

//Custom sort function of the chords to keep them in the original order
var chord = customChordLayout() //d3.layout.chord()//Custom sort function of the chords to keep them in the original order
	.padding(.02)
	.sortChords(d3.descending) //which chord should be shown on top when chords cross. Now the biggest chord is at the bottom
	.matrix(matrix);
	
var arc = d3.svg.arc()
	.innerRadius(innerRadius)
	.outerRadius(outerRadius)
	.startAngle(startAngle) //startAngle and endAngle now include the offset in degrees
	.endAngle(endAngle);

var path = stretchedChord()
	.radius(innerRadius)
	.startAngle(startAngle)
	.endAngle(endAngle)
	.pullOutSize(pullOutSize);

////////////////////////////////////////////////////////////
//////////////////// Draw outer Arcs ///////////////////////
////////////////////////////////////////////////////////////

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

g.append("path")
	.style("stroke", function(d,i) { return (Names[i] === "" ? "none" : "#00A1DE"); })
	.style("fill", function(d,i) { return (Names[i] === "" ? "none" : "#00A1DE"); })
	.style("pointer-events", function(d,i) { return (Names[i] === "" ? "none" : "auto"); })
	.attr("d", arc)
	.attr("transform", function(d, i) { //Pull the two slices apart
				d.pullOutSize = pullOutSize * ( d.startAngle + 0.001 > Math.PI ? -1 : 1);
				return "translate(" + d.pullOutSize + ',' + 0 + ")";
	});


////////////////////////////////////////////////////////////
////////////////////// Append Names ////////////////////////
////////////////////////////////////////////////////////////

//The text also needs to be displaced in the horizontal directions
//And also rotated with the offset in the clockwise direction
g.append("text")
	.each(function(d) { d.angle = ((d.startAngle + d.endAngle) / 2) + offset;})
	.attr("dy", ".35em")
	.attr("class", "titles")
	.attr("text-anchor", function(d) { return d.angle > Math.PI ? "end" : null; })
	.attr("transform", function(d,i) { 
		var c = arc.centroid(d);
		return "translate(" + (c[0] + d.pullOutSize) + "," + c[1] + ")"
		+ "rotate(" + (d.angle * 180 / Math.PI - 90) + ")"
		+ "translate(" + 55 + ",0)"
		+ (d.angle > Math.PI ? "rotate(180)" : "")
	})
  .text(function(d,i) { return Names[i]; });

////////////////////////////////////////////////////////////
//////////////////// Draw inner chords /////////////////////
////////////////////////////////////////////////////////////
 
var chords = wrapper.selectAll("path.chord")
	.data(chord.chords)
	.enter().append("path")
	.attr("class", "chord")
	.style("stroke", "none")
	.style("fill", "#C4C4C4")
	.style("opacity", function(d) { return (Names[d.source.index] === "" ? 0 : opacityDefault); }) //Make the dummy strokes have a zero opacity (invisible)
	.style("pointer-events", function(d,i) { return (Names[d.source.index] === "" ? "none" : "auto"); }) //Remove pointer events from dummy strokes
	.attr("d", path);	

////////////////////////////////////////////////////////////
///////////////////////// Tooltip //////////////////////////
////////////////////////////////////////////////////////////

//Arcs
g.append("title")	
	.text(function(d, i) {return Math.round(d.value) + " people in " + Names[i];});
	
//Chords
chords.append("title")
	.text(function(d) {
		return [Math.round(d.source.value), " people from ", Names[d.target.index], " to ", Names[d.source.index]].join(""); 
	});
	
////////////////////////////////////////////////////////////
////////////////// Extra Functions /////////////////////////
////////////////////////////////////////////////////////////

//Include the offset in de start and end angle to rotate the Chord diagram clockwise
function startAngle(d) { return d.startAngle + offset; }
function endAngle(d) { return d.endAngle + offset; }

// 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 && Names[d.source.index] !== ""; })
		.transition("fadeOnArc")
		.style("opacity", opacity);
  };
}//fade

thumbnail.png

This is yummy. I want to do the exact same thing using Swift on a native app. Thanks for sharing.