chart = StackedBarChart(stateages, {
x: d => d.state,
y: d => d.population / 1e6,
z: d => d.age,
xDomain: d3.groupSort(stateages, D => d3.sum(D, d => -d.population), d => d.state),
yLabel: "↑ Population (millions)",
zDomain: ages,
colors: d3.schemeSpectral[ages.length],
width,
height: 500
})
states = FileAttachment("us-population-state-age.csv").csv({typed: true})
ages = states.columns.slice(1)
stateages = ages.flatMap(age => states.map(d => ({state: d.name, age, population: d[age]}))) // pivot longer
// Copyright 2021 Observable, Inc.
// Released under the ISC license.
// https://observablehq.com/@d3/stacked-bar-chart
function StackedBarChart(data, {
x = (d, i) => i, // given d in data, returns the (ordinal) x-value
y = d => d, // given d in data, returns the (quantitative) y-value
z = () => 1, // given d in data, returns the (categorical) z-value
title, // given d in data, returns the title text
marginTop = 30, // top margin, in pixels
marginRight = 0, // right margin, in pixels
marginBottom = 30, // bottom margin, in pixels
marginLeft = 40, // left margin, in pixels
width = 640, // outer width, in pixels
height = 400, // outer height, in pixels
xDomain, // array of x-values
xRange = [marginLeft, width - marginRight], // [left, right]
xPadding = 0.1, // amount of x-range to reserve to separate bars
yType = d3.scaleLinear, // type of y-scale
yDomain, // [ymin, ymax]
yRange = [height - marginBottom, marginTop], // [bottom, top]
zDomain, // array of z-values
offset = d3.stackOffsetDiverging, // stack offset method
order = d3.stackOrderNone, // stack order method
yFormat, // a format specifier string for the y-axis
yLabel, // a label for the y-axis
colors = d3.schemeTableau10, // array of colors
} = {}) {
// Compute values.
const X = d3.map(data, x);
const Y = d3.map(data, y);
const Z = d3.map(data, z);
// Compute default x- and z-domains, and unique them.
if (xDomain === undefined) xDomain = X;
if (zDomain === undefined) zDomain = Z;
xDomain = new d3.InternSet(xDomain);
zDomain = new d3.InternSet(zDomain);
// Omit any data not present in the x- and z-domains.
const I = d3.range(X.length).filter(i => xDomain.has(X[i]) && zDomain.has(Z[i]));
// Compute a nested array of series where each series is [[y1, y2], [y1, y2],
// [y1, y2], …] representing the y-extent of each stacked rect. In addition,
// each tuple has an i (index) property so that we can refer back to the
// original data point (data[i]). This code assumes that there is only one
// data point for a given unique x- and z-value.
const series = d3.stack()
.keys(zDomain)
.value(([x, I], z) => Y[I.get(z)])
.order(order)
.offset(offset)
(d3.rollup(I, ([i]) => i, i => X[i], i => Z[i]))
.map(s => s.map(d => Object.assign(d, {i: d.data[1].get(s.key)})));
// Compute the default y-domain. Note: diverging stacks can be negative.
if (yDomain === undefined) yDomain = d3.extent(series.flat(2));
// Construct scales, axes, and formats.
const xScale = d3.scaleBand(xDomain, xRange).paddingInner(xPadding);
const yScale = yType(yDomain, yRange);
const color = d3.scaleOrdinal(zDomain, colors);
const xAxis = d3.axisBottom(xScale).tickSizeOuter(0);
const yAxis = d3.axisLeft(yScale).ticks(height / 60, yFormat);
// Compute titles.
if (title === undefined) {
const formatValue = yScale.tickFormat(100, yFormat);
title = i => `${X[i]}\n${Z[i]}\n${formatValue(Y[i])}`;
} else {
const O = d3.map(data, d => d);
const T = title;
title = i => T(O[i], i, data);
}
const svg = d3.create("svg")
.attr("width", width)
.attr("height", height)
.attr("viewBox", [0, 0, width, height])
.attr("style", "max-width: 100%; height: auto; height: intrinsic;");
svg.append("g")
.attr("transform", `translate(${marginLeft},0)`)
.call(yAxis)
.call(g => g.select(".domain").remove())
.call(g => g.selectAll(".tick line").clone()
.attr("x2", width - marginLeft - marginRight)
.attr("stroke-opacity", 0.1))
.call(g => g.append("text")
.attr("x", -marginLeft)
.attr("y", 10)
.attr("fill", "currentColor")
.attr("text-anchor", "start")
.text(yLabel));
const bar = svg.append("g")
.selectAll("g")
.data(series)
.join("g")
.attr("fill", ([{i}]) => color(Z[i]))
.selectAll("rect")
.data(d => d)
.join("rect")
.attr("x", ({i}) => xScale(X[i]))
.attr("y", ([y1, y2]) => Math.min(yScale(y1), yScale(y2)))
.attr("height", ([y1, y2]) => Math.abs(yScale(y1) - yScale(y2)))
.attr("width", xScale.bandwidth());
if (title) bar.append("title")
.text(({i}) => title(i));
svg.append("g")
.attr("transform", `translate(0,${yScale(0)})`)
.call(xAxis);
return Object.assign(svg.node(), {scales: {color}});
}
import {Legend, Swatches} from "@d3/color-legend"
import {howto, altplot} from "@d3/example-components"
One platform to build and deploy the best data apps
Experiment and prototype by building visualizations in live JavaScript notebooks. Collaborate with your team and decide which concepts to build out.
Use Observable Framework to build data apps locally. Use data loaders to build in any language or library, including Python, SQL, and R.
Seamlessly deploy to Observable. Test before you ship, use automatic deploy-on-commit, and ensure your projects are always up-to-date.