Most basic network chart in d3.js




This post describes how to build a very basic network chart with d3.js. You can see many other examples in the network graph section of the gallery. Learn more about network charts in d3.js here.


Network section

Steps:

  • First of all, it is important to understand that network input data is composed by a list of nodes and a list of links. Have a look to the data.

  • After the d3.csv() call, you can do console.log(data.links) to check how the data looks like.

  • In the links part, elements must be called source and target to be recognized by d3
<!DOCTYPE html>
<meta charset="utf-8">

<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>

<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>


<script>

// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 40},
  width = 400 - margin.left - margin.right,
  height = 400 - margin.top - margin.bottom;

// append the svg object to the body of the page
var svg = d3.select("#my_dataviz")
.append("svg")
  .attr("width", width + margin.left + margin.right)
  .attr("height", height + margin.top + margin.bottom)
.append("g")
  .attr("transform",
        "translate(" + margin.left + "," + margin.top + ")");

d3.json("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/data_network.json", function( data) {

  // Initialize the links
  var link = svg
    .selectAll("line")
    .data(data.links)
    .enter()
    .append("line")
      .style("stroke", "#aaa")

  // Initialize the nodes
  var node = svg
    .selectAll("circle")
    .data(data.nodes)
    .enter()
    .append("circle")
      .attr("r", 20)
      .style("fill", "#69b3a2")

  // Let's list the force we wanna apply on the network
  var simulation = d3.forceSimulation(data.nodes)                 // Force algorithm is applied to data.nodes
      .force("link", d3.forceLink()                               // This force provides links between nodes
            .id(function(d) { return d.id; })                     // This provide  the id of a node
            .links(data.links)                                    // and this the list of links
      )
      .force("charge", d3.forceManyBody().strength(-400))         // This adds repulsion between nodes. Play with the -400 for the repulsion strength
      .force("center", d3.forceCenter(width / 2, height / 2))     // This force attracts nodes to the center of the svg area
      .on("end", ticked);

  // This function is run at each iteration of the force algorithm, updating the nodes position.
  function ticked() {
    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+6; })
         .attr("cy", function(d) { return d.y-6; });
  }

});


</script>

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