Visualization toolmaker. Founder @observablehq. Creator @d3. Former @nytgraphics. Pronounced BOSS-tock.
chart = {
const path = d3.geoPath();
const svg = d3.create("svg")
.attr("viewBox", "0 0 960 600")
.style("width", "100%")
.style("height", "auto");
svg.append("g")
.attr("transform", "translate(600,40)")
.call(legend);
svg.append("g")
.selectAll("path")
.data(topojson.feature(us, us.objects.counties).features)
.join("path")
.attr("fill", d => color(data.get(d.id)))
.attr("d", path)
.append("title")
.text(d => `${d.properties.name}, ${states.get(d.id.slice(0, 2)).name}
${format(data.get(d.id))}`);
svg.append("path")
.datum(topojson.mesh(us, us.objects.states, (a, b) => a !== b))
.attr("fill", "none")
.attr("stroke", "white")
.attr("stroke-linejoin", "round")
.attr("d", path);
return svg.node();
}
legend = g => {
const width = 240;
g.append("image")
.attr("width", width)
.attr("height", 8)
.attr("preserveAspectRatio", "none")
.attr("xlink:href", ramp(color.interpolator()).toDataURL());
g.append("text")
.attr("class", "caption")
.attr("y", -6)
.attr("fill", "#000")
.attr("text-anchor", "start")
.attr("font-weight", "bold")
.text(data.title);
g.call(d3.axisBottom(d3.scaleLinear(color.domain(), [0, width / 2, width]))
.ticks(6)
.tickFormat(d => `${d > 0 ? "+" : ""}${(d * 100).toFixed(0)}`)
.tickSize(13))
.select(".domain")
.remove();
}
data = Object.assign(new Map(d3.zip(...await Promise.all([10, 11].map(fetchPopulation))).map(([[id2017, population2017], [id2018, population2018]]) => {
if (id2017 !== id2018) throw new Error;
return [id2017, Math.round((population2018 - population2017) / population2017 * 1000) / 1000];
})), {title: "Population change (%)"})
function fetchPopulation(date) {
return d3.json("https://api.census.gov/data/2018/pep/population?get=POP&for=county:*&DATE_CODE=" + date).then(rows => rows.slice(1).sort((a, b) => d3.ascending(a[2], b[2]) || d3.ascending(a[3], b[3])).map(([population,, state, county]) => [state + county, +population]));
}
color = d3.scaleDiverging([-0.03, 0, 0.03], d3.interpolateRdBu)
format = d3.format("+.1%")
states = new Map(us.objects.states.geometries.map(d => [d.id, d.properties]))
us = FileAttachment("counties-albers-10m.json").json()
topojson = require("topojson-client@3")
d3 = require("d3@5")
import {ramp} from "@mbostock/color-ramp"
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