Force-Directed Graph with tooltip / Maeve Kane

chart = {

const links = data.links.map(d => Object.create(d));

const nodes = data.nodes.map(d => Object.create(d));

const simulation = d3

.forceSimulation(nodes)

.force("link", d3.forceLink(links).id(d => d.id))

.force("charge", d3.forceManyBody())

.force("center", d3.forceCenter(width / 2, height / 2))

.force("collision", d3.forceCollide(d => d.degree + 2));

const svg = d3

.create("svg")

.attr("height", height)

.attr("width", width);

const link = svg

.append("g")

.attr("stroke", "#999")

.attr("stroke-opacity", 0.6)

.selectAll("line")

.data(links)

.join("line")

.attr("stroke-width", d => Math.sqrt(d.value));

const node = svg

.append("g")

.attr("stroke", "#fff")

.attr("stroke-width", 1.5)

.selectAll("circle")

.data(nodes)

.join("circle")

.attr("r", d => d.degree + 2)

.attr("fill", color)

.on("mouseover", tooltip_in) // when the mouse hovers a node, call the tooltip_in function to create the tooltip

.on("mouseout", tooltip_out) // when the mouse stops hovering a node, call the tooltip_out function to get rid of the tooltip

.call(drag(simulation));

simulation.on("tick", () => {

link

.attr("x1", d => d.source.x)

.attr("y1", d => d.source.y)

.attr("x2", d => d.target.x)

.attr("y2", d => d.target.y);

node.attr("cx", d => d.x).attr("cy", d => d.y);

});

return svg.node();

}

// name a variable tooltip, and style it using css properties

tooltip = d3

.select("body")

.append("div") // the tooltip always "exists" as its own html div, even when not visible

.style("position", "absolute") // the absolute position is necessary so that we can manually define its position later

.style("visibility", "hidden") // hide it from default at the start so it only appears on hover

.style("background-color", "white")

.attr("class", "tooltip")

//name a tooltip_in function to call when the mouse hovers a node

tooltip_in = function(event, d) { // pass event and d to this function so that it can access d for our data

return tooltip

.html("<h4>" + d.id + "</h4>") // add an html element with a header tag containing the name of the node. This line is where you would add additional information like: "<h4>" + d.name + "</h4></br><p>" + d.type + "</p>" Note the quote marks, pluses and </br>--these are necessary for javascript to put all the data and strings within quotes together properly. Any text needs to be all one line in .html() here

.style("visibility", "visible") // make the tooltip visible on hover

.style("top", event.pageY + "px") // position the tooltip with its top at the same pixel location as the mouse on the screen

.style("left", event.pageX + "px"); // position the tooltip just to the right of the mouse location

}

// name a tooltip_out function to call when the mouse stops hovering

tooltip_out = function() {

return tooltip

.transition()

.duration(50) // give the hide behavior a 50 milisecond delay so that it doesn't jump around as the network moves

.style("visibility", "hidden"); // hide the tooltip when the mouse stops hovering

}

// this is some optional tooltip styling to make it look nice. This just uses regular css

html`

.tooltip {

fill: white;

font-family: sans-serif;

padding: 5px;

border-radius: 5px;

border: 1px solid grey;

}

</style>

`

md`### Get the data file`

data = FileAttachment("graph (1).json").json()

md`### Define height`

height = 600

md`### Define the color scale`

color = {

const scale = d3.scaleOrdinal(d3.schemeCategory10);

return d => scale(d.modularity);

}

md`### Handle dragging`

drag = simulation => {

function dragstarted(event) {

if (!event.active) simulation.alphaTarget(0.3).restart();

event.subject.fx = event.subject.x;

event.subject.fy = event.subject.y;

}

function dragged(event) {

event.subject.fx = event.x;

event.subject.fy = event.y;

}

function dragended(event) {

if (!event.active) simulation.alphaTarget(0);

event.subject.fx = null;

event.subject.fy = null;

}

return d3.drag()

.on("start", dragstarted)

.on("drag", dragged)

.on("end", dragended);

}

md`### Include D3`

d3 = require("d3@6")

Purpose-built for displays of data