Adaptation of Mike Bostock's Force-Directed Graph of Les Mis Characters using .csv dataset instead of json

##Fork of Mike Bostock's original force-directed example. This fork uses an ugly csv which unfortunately is just a fact of life in my world. JSON is highly recommended unless it is unavailable.

##Original readme.md is below and does a very nice job of explaining the graph.

This simple force-directed graph shows character co-occurence in Les Misérables. A physical simulation of charged particles and springs places related characters in closer proximity, while unrelated characters are farther apart. Layout algorithm inspired by Tim Dwyer and Thomas Jakobsen. Data based on character coappearence in Victor Hugo's Les Misérables, compiled by Donald Knuth.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

.node {
  stroke: #fff;
  stroke-width: 1.5px;
}

.link {
  stroke: #999;
  stroke-opacity: .6;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.js"></script>
<script>

var width = 960,
        height = 500;

var color = d3.scale.category20();

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

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

d3.csv("les_mis.csv", function (error, data) {
        //set up graph in same style as original example but empty
        graph = { "nodes": [], "links": [] };

//loop through each link record from the csv data
        //add to the nodes each source and target; we'll reduce to unique values later
        //add to the links each source, target record with the value (if desired, multiple value fields can be added)
        data.forEach(function (d) {
            graph.nodes.push({ "name": d.source, "group": +d.groupsource });
            graph.nodes.push({ "name": d.target, "group": +d.grouptarget });

graph.links.push({ "source": d.source, "target": d.target, "value": +d.value });
        });

//use this as temporary holding while we manipulate graph.nodes
        //this will contain a map object containing an object for each node
        //within each node object there will be a child object for each instance that node appear
        //however, using rollup we can eliminate this duplication
        var nodesmap = d3.nest()
                            .key(function (d) { return d.name; })
                            .rollup(function (d) { return { "name": d[0].name, "group": d[0].group }; })
                            .map(graph.nodes);

//thanks Mike Bostock https://groups.google.com/d/msg/d3-js/pl297cFtIQk/Eso4q_eBu1IJ
        //this handy little function returns only the distinct / unique nodes
        graph.nodes = d3.keys(d3.nest()
                             .key(function (d) { return d.name; })
                             .map(graph.nodes));

//it appears d3 with force layout wants a numeric source and target
        //so loop through each link replacing the text with its index from node
        graph.links.forEach(function (d, i) {
            graph.links[i].source = graph.nodes.indexOf(graph.links[i].source);
            graph.links[i].target = graph.nodes.indexOf(graph.links[i].target);
        });

//this is not in the least bit pretty
        //will get graph.nodes in its final useable form
        //loop through each unique node and replace with an object with same numeric key and name/group as properties
        //that will come from the nodesmap that we defined earlier
        graph.nodes.forEach(function (d,i) { graph.nodes[i]={ "name": nodesmap[d].name, "group": nodesmap[d].group }; })

force
          .nodes(graph.nodes)
          .links(graph.links)
          .start();

var link = svg.selectAll(".link")
          .data(graph.links)
        .enter().append("line")
          .attr("class", "link")
          .style("stroke-width", function (d) { return Math.sqrt(d.value); });

var node = svg.selectAll(".node")
          .data(graph.nodes)
        .enter().append("circle")
          .attr("class", "node")
          .attr("r", 5)
          .style("fill", function (d) { return color(d.group); })
          .call(force.drag);

node.append("title")
          .text(function (d) { return d.name; });

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 d.y; });
        });
    });

</script>        
</body>
</html>

Modified http://d3js.org/d3.v3.js to a secure url

https://d3js.org/d3.v3.js