Published
Edited
May 29, 2021
1 fork
md`# Annual PM2.5 Concentrations Bar Chart Race`
data = FileAttachment("Average_PM₂̣_₅ 2010-2018@4.csv").csv({typed: true})
viewof replay = html`<button>Replay`
chart = {
replay;
const svg = d3.create("svg")
.attr("viewBox", [0, 0, width, height]);
const updateBars = bars(svg);
const updateAxis = axis(svg);
const updateLabels = labels(svg);
const updateTicker = ticker(svg);
yield svg.node();
for (const keyframe of keyframes) {
const transition = svg.transition()
.duration(duration)
.ease(d3.easeLinear);
// Extract the top bar’s value.
x.domain([0, keyframe[1][0].value]);
updateAxis(keyframe, transition);
updateBars(keyframe, transition);
updateLabels(keyframe, transition);
updateTicker(keyframe, transition);
invalidation.then(() => svg.interrupt());
await transition.end();
}
}
duration = 250
n = 15
names = new Set(data.map(d => d.name))
datevalues = Array.from(d3.rollup(data, ([d]) => d.value, d => +d.date, d => d.name))
.map(([date, data]) => [new Date(date), data])
.sort(([a], [b]) => d3.ascending(a, b))
function rank(value) {
const data = Array.from(names, name => ({name, value: value(name)}));
data.sort((a, b) => d3.descending(a.value, b.value));
for (let i = 0; i < data.length; ++i) data[i].rank = Math.min(n, i);
return data;
}
k = 15
keyframes = {
const keyframes = [];
let ka, a, kb, b;
for ([[ka, a], [kb, b]] of d3.pairs(datevalues)) {
for (let i = 0; i < k; ++i) {
const t = i / k;
keyframes.push([
new Date(ka * (1 - t) + kb * t),
rank(name => (a.get(name) || 0) * (1 - t) + (b.get(name) || 0) * t)
]);
}
}
keyframes.push([new Date(kb), rank(name => b.get(name) || 0)]);
return keyframes;
}
nameframes = d3.groups(keyframes.flatMap(([, data]) => data), d => d.name)
prev = new Map(nameframes.flatMap(([, data]) => d3.pairs(data, (a, b) => [b, a])))
next = new Map(nameframes.flatMap(([, data]) => d3.pairs(data)))
function bars(svg) {
let bar = svg.append("g")
.attr("fill-opacity", 0.6)
.selectAll("rect");
return ([date, data], transition) => bar = bar
.data(data.slice(0, n), d => d.name)
.join(
enter => enter.append("rect")
.attr("fill", color)
.attr("height", y.bandwidth())
.attr("x", x(0))
.attr("y", d => y((prev.get(d) || d).rank))
.attr("width", d => x((prev.get(d) || d).value) - x(0)),
update => update,
exit => exit.transition(transition).remove()
.attr("y", d => y((next.get(d) || d).rank))
.attr("width", d => x((next.get(d) || d).value) - x(0))
)
.call(bar => bar.transition(transition)
.attr("y", d => y(d.rank))
.attr("width", d => x(d.value) - x(0)));
}
function labels(svg) {
let label = svg.append("g")
.style("font", "bold 12px var(--sans-serif)")
.style("font-variant-numeric", "tabular-nums")
.attr("text-anchor", "end")
.selectAll("text");
return ([date, data], transition) => label = label
.data(data.slice(0, n), d => d.name)
.join(
enter => enter.append("text")
.attr("transform", d => `translate(${x((prev.get(d) || d).value)},${y((prev.get(d) || d).rank)})`)
.attr("y", y.bandwidth() / 2)
.attr("x", -6)
.attr("dy", "-0.25em")
.text(d => d.name)
.call(text => text.append("tspan")
.attr("fill-opacity", 0.7)
.attr("font-weight", "normal")
.attr("x", -6)
.attr("dy", "1.15em")),
update => update,
exit => exit.transition(transition).remove()
.attr("transform", d => `translate(${x((next.get(d) || d).value)},${y((next.get(d) || d).rank)})`)
.call(g => g.select("tspan").tween("text", d => textTween(d.value, (next.get(d) || d).value)))
)
.call(bar => bar.transition(transition)
.attr("transform", d => `translate(${x(d.value)},${y(d.rank)})`)
.call(g => g.select("tspan").tween("text", d => textTween((prev.get(d) || d).value, d.value))));
}
function textTween(a, b) {
const i = d3.interpolateNumber(a, b);
return function(t) {
this.textContent = formatNumber(i(t));
};
}
formatNumber = d3.format(",d")
tickFormat = undefined // override as desired
function axis(svg) {
const g = svg.append("g")
.attr("transform", `translate(0,${margin.top})`);
const axis = d3.axisTop(x)
.ticks(width / 160, tickFormat)
.tickSizeOuter(0)
.tickSizeInner(-barSize * (n + y.padding()));
return (_, transition) => {
g.transition(transition).call(axis);
g.select(".tick:first-of-type text").remove();
g.selectAll(".tick:not(:first-of-type) line").attr("stroke", "white");
g.select(".domain").remove();
};
}
function ticker(svg) {
const now = svg.append("text")
.style("font", `bold ${barSize}px var(--sans-serif)`)
.style("font-variant-numeric", "tabular-nums")
.attr("text-anchor", "end")
.attr("x", width - 6)
.attr("y", margin.top + barSize * (n - 0.45))
.attr("dy", "0.32em")
.text(formatDate(keyframes[0][0]));
return ([date], transition) => {
transition.end().then(() => now.text(formatDate(date)));
};
}
formatDate = d3.utcFormat("%Y")
color = {
const scale = d3.scaleOrdinal(d3.schemePaired);
if (data.some(d => d.category !== undefined)) {
const categoryByName = new Map(data.map(d => [d.name, d.category]))
scale.domain(categoryByName.values());
return d => scale(categoryByName.get(d.name));
}
return d => scale(d.name);
}
x = d3.scaleLinear([0, 1], [margin.left, width - margin.right])
y = d3.scaleBand()
.domain(d3.range(n + 1))
.rangeRound([margin.top, margin.top + barSize * (n + 1 + 0.1)])
.padding(0.1)
height = margin.top + barSize * n + margin.bottom
barSize = 30
margin = ({top: 16, right: 6, bottom: 6, left: 0})
d3 = require("d3@6")
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Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
