erkal/README.md

## README.md

      
    Raw
  

              README.md
            
          
    Using Invisible Nodes

This is supposed to be an answer to this question.
It combines this example with the use of invisible nodes.

  
## index.html
<!DOCTYPE html>
<meta charset="utf-8">

<style>
.link {
  stroke: black;
  stroke-width: 2px;
}
.node {
  stroke: white;
  stroke-width: 2px;
}
</style>

<body>
<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script>
<script>

var width = 960, height = 500, colors = d3.scale.category10();

var n = 200,
    k = 7,
    nodes = d3.range(n).map(function (num) { return {type: num % k, charge: -50} }),
    links = d3.range(1,n).map(function (a) { return {source: nodes[0], target: nodes[a]} });

    nodes[0].fixed = true;
    nodes[0].x = 480;
    nodes[0].y = 250;

var invisibleNodes = d3.range(k).map(function () { return {charge: -1000} }),
    invisibleLinks = invisibleNodes.map(function (a) { return {source: 0, target: a} });

var force = d3.layout.force()
    .size([width, height])
    .nodes(nodes.concat(invisibleNodes))
    .links(invisibleLinks)
    .charge(function (d) { return d.charge })
    .on("tick", tick)
    .start();

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

svgLinks = svg.selectAll(".link").data(links)
  .enter().append("line")
    .attr("class", "link")

svgNodes = svg.selectAll(".node").data(nodes)
  .enter().append("circle")
    .attr("class", "node")
    .attr("r", 8)
    .style("fill", function (d) { return colors(d.type) })
    .call(force.drag);

function tick(e) {
  var k = .3 * e.alpha;

  // Push nodes toward their designated focus.
  nodes.forEach(function(o, i) {
    o.y += (invisibleNodes[o.type].y - o.y) * k;
    o.x += (invisibleNodes[o.type].x - o.x) * k;
  });

  svgNodes
      .attr("cx", function(d) { return d.x })
      .attr("cy", function(d) { return d.y });

  svgLinks
      .attr("x1", function(d) { return d.source.x })
      .attr("y1", function(d) { return d.source.y })
      .attr("x2", function(d) { return d.target.x })
      .attr("y2", function(d) { return d.target.y });
};

</script>

## thumbnail.png

      
    Raw
  

              thumbnail.png
	<!DOCTYPE html>
	<meta charset="utf-8">

	<style>
	.link {
	stroke: black;
	stroke-width: 2px;
	}
	.node {
	stroke: white;
	stroke-width: 2px;
	}
	</style>

	<body>
	<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script>
	<script>

	var width = 960, height = 500, colors = d3.scale.category10();

	var n = 200,
	k = 7,
	nodes = d3.range(n).map(function (num) { return {type: num % k, charge: -50} }),
	links = d3.range(1,n).map(function (a) { return {source: nodes[0], target: nodes[a]} });

	nodes[0].fixed = true;
	nodes[0].x = 480;
	nodes[0].y = 250;

	var invisibleNodes = d3.range(k).map(function () { return {charge: -1000} }),
	invisibleLinks = invisibleNodes.map(function (a) { return {source: 0, target: a} });

	var force = d3.layout.force()
	.size([width, height])
	.nodes(nodes.concat(invisibleNodes))
	.links(invisibleLinks)
	.charge(function (d) { return d.charge })
	.on("tick", tick)
	.start();

	var svg = d3.select("body").append("svg")
	.attr("width", width)
	.attr("height", height);

	svgLinks = svg.selectAll(".link").data(links)
	.enter().append("line")
	.attr("class", "link")

	svgNodes = svg.selectAll(".node").data(nodes)
	.enter().append("circle")
	.attr("class", "node")
	.attr("r", 8)
	.style("fill", function (d) { return colors(d.type) })
	.call(force.drag);

	function tick(e) {
	var k = .3 * e.alpha;

	// Push nodes toward their designated focus.
	nodes.forEach(function(o, i) {
	o.y += (invisibleNodes[o.type].y - o.y) * k;
	o.x += (invisibleNodes[o.type].x - o.x) * k;
	});

	svgNodes
	.attr("cx", function(d) { return d.x })
	.attr("cy", function(d) { return d.y });

	svgLinks
	.attr("x1", function(d) { return d.source.x })
	.attr("y1", function(d) { return d.source.y })
	.attr("x2", function(d) { return d.target.x })
	.attr("y2", function(d) { return d.target.y });
	};

	</script>