d3app_s1

Basic force directed layout

by Simon Raper

HTML

<script src="http://labratrevenge.com/d3-tip/javascripts/d3.tip.v0.6.3.js"></script>
<div id ="chart"></div>

CSS

.node {
    stroke: #fff;
    stroke-width: 1.5px;
}
.link {
    stroke: #999;
    stroke-opacity: .6;
}

JavaScript

var url = "https://afternoon-anchorage-24816.herokuapp.com/api/data?audience=younger_segment"


var dispatcher = d3.dispatch('jsonLoad');

d3.select('#loadData').on('click', function() {
    d3.json(url, callback);
});

// optional dispatcher
dispatcher.on('jsonLoad', function(data) {
    // triggered afer json is loaded (just if you want to do additional stuff here.)
    console.log(data);
});

var callback = function (error, root) {
        dispatcher.jsonLoad(root); 

//Constants for the SVG
var width = 500,
    height = 500;

//Set up the force layout
var force = d3.layout.force()
    .charge(-120)
    .linkDistance(30)
    .size([width, height]);

//Append a SVG to the body of the html page. Assign this SVG as an object to svg
var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);


//Creates the graph data structure out of the json data
force.nodes(graph.nodes)
    .links(graph.links)
    .start();

//Create all the line svgs but without locations yet
var link = svg.selectAll(".link")
    .data(graph.links)
    .enter().append("line")
    .attr("class", "link")
    .style("stroke-width", function (d) {
    return Math.sqrt(d.value);
});

//Do the same with the circles for the nodes - no 
var node = svg.selectAll(".node")
    .data(graph.nodes)
    .enter().append("circle")
    .attr("class", "node")
    .attr("r", 8)
    .call(force.drag);


//Now we are giving the SVGs co-ordinates - the force layout is generating the co-ordinates which this code is using to update the attributes of the SVG elements
force.on("tick", function () {
    link.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;
    });

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