Published
Edited
Jun 27, 2019
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chart = {
// const svg = d3.select(DOM.svg(width, height));
// svg.append("g")
// .call(xAxis);
const svg = d3.select(DOM.svg(width, height));
svg.append("g")
.call(xAxis);
// svg.append("g")
// .selectAll("circle")
// .data(dodge(data, radius * 2 + padding))
// .enter().append("circle")
// .attr("cx", d => d.x)
// .attr("cy", d => height / 2 + d.y)
// .attr("r", radius)
// .append("title")
// .text(d => d.data.name);

// return svg.node();
svg.append("g")
.selectAll("circle")
.data(dodge(data, radius * 2 + padding))
.enter().append("circle")
.attr("cx", d=> d.x)
.attr("cy", d=> height /2 + d.y)
.attr("r", radius)
.append("title")
.text(d => d.data.name);
return svg.node();
}
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dodge = (data, radius) => {
const radius2 = radius ** 2;
const circles = data.map(d => ({x: x(d.value), data: d})).sort((a, b) => a.x - b.x);
const epsilon = 1e-3;
let head = null, tail = null;

// Returns true if circle ⟨x,y⟩ intersects with any circle in the queue.
function intersects(x, y) {
let a = head;
while (a) {
if (radius2 - epsilon > (a.x - x) ** 2 + (a.y - y) ** 2) {
return true;
}
a = a.next;
}
return false;
}

// Place each circle sequentially.
for (const b of circles) {

// Remove circles from the queue that can’t intersect the new circle b.
while (head && head.x < b.x - radius2) head = head.next;

// Choose the minimum non-intersecting tangent.
if (intersects(b.x, b.y = 0)) {
let a = head;
b.y = Infinity;
do {
let y1 = a.y + Math.sqrt(radius2 - (a.x - b.x) ** 2);
let y2 = a.y - Math.sqrt(radius2 - (a.x - b.x) ** 2);
if (Math.abs(y1) < Math.abs(b.y) && !intersects(b.x, y1)) b.y = y1;
if (Math.abs(y2) < Math.abs(b.y) && !intersects(b.x, y2)) b.y = y2;
a = a.next;
} while (a);
}

// Add b to the queue.
b.next = null;
if (head === null) head = tail = b;
else tail = tail.next = b;
}

return circles;
}
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data = (await require("@observablehq/cars")).map(({Name: name, Weight_in_lbs: value}) => ({name, value}))
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x = d3.scaleLinear()
.domain(d3.extent(data, d => d.value))
.range([margin.left, width - margin.right])
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xAxis = g => g
.attr("transform", `translate(0,${height - margin.bottom})`)
.call(d3.axisBottom(x).tickSizeOuter(0))
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height = 240
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radius = 3
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padding = 1.5
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margin = ({top: 20, right: 20, bottom: 30, left: 20})
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d3 = require("d3@5")
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