Based on Mike Bostock's force-directed graph example showing character co-occurence in Les Misérables, this gist shows how to implement a dynamic link-display threshold. (The slider is based on Bostock's "brush as slider" block.) See this blog post on bilateral migration for an example use case.
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<meta charset="utf-8">
<style>
.node {
stroke: #fff;
stroke-width: 1.5px;
}
.link {
stroke: #999;
stroke-opacity: .6;
}
.axis {
opacity: 0.5;
font: 10px sans-serif;
-webkit-user-select: none;
-moz-user-select: none;
user-select: none;
}
.axis .domain {
fill: none;
stroke: #000;
stroke-opacity: .3;
stroke-width: 4px;
stroke-linecap: round;
}
.axis .halo {
fill: none;
stroke: #ddd;
stroke-width: 3px;
stroke-linecap: round;
}
.slider .handle {
fill: #fff;
stroke: #000;
stroke-opacity: .5;
stroke-width: 1.25px;
cursor: grab;
}
</style>
<body>
<script src="https://d3js.org/d3.v3.min.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 x = d3.scale.linear()
.domain([0, 20])
.range([250, 80])
.clamp(true);
var brush = d3.svg.brush()
.y(x)
.extent([0, 0]);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height);
var links_g = svg.append("g");
var nodes_g = svg.append("g");
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(" + (width - 20) + ",0)")
.call(d3.svg.axis()
.scale(x)
.orient("left")
.tickFormat(function(d) { return d; })
.tickSize(0)
.tickPadding(12))
.select(".domain")
.select(function() { return this.parentNode.appendChild(this.cloneNode(true)); })
.attr("class", "halo");
var slider = svg.append("g")
.attr("class", "slider")
.call(brush);
slider.selectAll(".extent,.resize")
.remove();
var handle = slider.append("circle")
.attr("class", "handle")
.attr("transform", "translate(" + (width - 20) + ",0)")
.attr("r", 5);
svg.append("text")
.attr("x", width - 15)
.attr("y", 60)
.attr("text-anchor", "end")
.attr("font-size", "12px")
.style("opacity", 0.5)
.text("co-occurence threshold")
d3.json("miserables.json", function(error, graph) {
if (error) throw error;
graph.links.forEach(function(d,i){ d.i = i; });
function brushed() {
var value = brush.extent()[0];
if (d3.event.sourceEvent) {
value = x.invert(d3.mouse(this)[1]);
brush.extent([value, value]);
}
handle.attr("cy", x(value));
var threshold = value;
var thresholded_links = graph.links.filter(function(d){ return (d.value > threshold);});
force
.links(thresholded_links);
var link = links_g.selectAll(".link")
.data(thresholded_links, function(d){ return d.i; });
link.enter().append("line")
.attr("class", "link")
.style("stroke-width", function(d) { return Math.sqrt(d.value); });
link.exit().remove();
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; });
});
force.start();
}
force
.nodes(graph.nodes);
var node = nodes_g.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; });
brush.on("brush", brushed);
slider
.call(brush.extent([5, 5]))
.call(brush.event);
});
</script>
https://d3js.org/d3.v3.min.js