Published
Edited
Apr 2, 2020
3 forks
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md`# Networks and graphs
This module implements a velocity Verlet numerical integrator for simulating physical forces on particles. The simulation is simplified: it assumes a constant unit time step Δt = 1 for each step, and a constant unit mass m = 1 for all particles. As a result, a force F acting on a particle is equivalent to a constant acceleration a over the time interval Δt, and can be simulated simply by adding to the particle’s velocity, which is then added to the particle’s position.`
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d3 = require("d3@^5.9")
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graph = FileAttachment("miserables.json").json()
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network = {
var width = 960
var height = 600
var svg = d3.create("svg")
.attr("viewBox", [0, 0,960,600]);
var simulation = d3.forceSimulation()
.force("link", d3.forceLink().id(function(d) { return d.id; }))
.force("charge", d3.forceManyBody())
.force("center", d3.forceCenter(width / 2, height / 2));

var link = svg.append("g")
.attr("stroke", "red")
.selectAll("line")
.data(graph.links)
.enter().append("line");

var node = svg.append("g")
.attr("stroke-width", "480px")
.attr('pointer-events','all')
.attr('stroke','none')
.selectAll("circle")
.data(graph.nodes)
.enter().append("circle")
.attr("r", 2.5)
.call(d3.drag()
.on("start", dragstarted)
.on("drag", dragged)
.on("end", dragended));

node.append("title")
.text(function(d) { return 12; });

simulation
.nodes(graph.nodes)
.on("tick", ticked);

simulation.force("link")
.links(graph.links);

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

function dragstarted(d) {
if (!d3.event.active) simulation.alphaTarget(0.3).restart();
d.fx = d.x;
d.fy = d.y;
}

function dragged(d) {
d.fx = d3.event.x;
d.fy = d3.event.y;
}

function dragended(d) {
if (!d3.event.active) simulation.alphaTarget(0);
d.fx = null;
d.fy = null;
}
return svg.node();
}
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