chart = LineChart(unemployment, {
x: d => d.date,
y: d => d.unemployment,
z: d => d.division,
yLabel: "↑ Unemployment (%)",
width,
height: 500,
color: "steelblue",
voronoi // if true, show Voronoi overlay
})
unemployment = FileAttachment("bls-metro-unemployment.csv").csv({typed: true})
focus = Generators.input(chart) // or say viewof focus = LineChart(…)
// Copyright 2021 Observable, Inc.
// Released under the ISC license.
// https://observablehq.com/@d3/multi-line-chart
function LineChart(data, {
x = ([x]) => x, // given d in data, returns the (temporal) x-value
y = ([, y]) => y, // 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
defined, // for gaps in data
curve = d3.curveLinear, // method of interpolation between points
marginTop = 20, // top margin, in pixels
marginRight = 30, // 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
xType = d3.scaleUtc, // type of x-scale
xDomain, // [xmin, xmax]
xRange = [marginLeft, width - marginRight], // [left, right]
yType = d3.scaleLinear, // type of y-scale
yDomain, // [ymin, ymax]
yRange = [height - marginBottom, marginTop], // [bottom, top]
yFormat, // a format specifier string for the y-axis
yLabel, // a label for the y-axis
zDomain, // array of z-values
color = "currentColor", // stroke color of line, as a constant or a function of *z*
strokeLinecap, // stroke line cap of line
strokeLinejoin, // stroke line join of line
strokeWidth = 1.5, // stroke width of line
strokeOpacity, // stroke opacity of line
mixBlendMode = "multiply", // blend mode of lines
voronoi // show a Voronoi overlay? (for debugging)
} = {}) {
// Compute values.
const X = d3.map(data, x);
const Y = d3.map(data, y);
const Z = d3.map(data, z);
const O = d3.map(data, d => d);
if (defined === undefined) defined = (d, i) => !isNaN(X[i]) && !isNaN(Y[i]);
const D = d3.map(data, defined);
// Compute default domains, and unique the z-domain.
if (xDomain === undefined) xDomain = d3.extent(X);
if (yDomain === undefined) yDomain = [0, d3.max(Y, d => typeof d === "string" ? +d : d)];
if (zDomain === undefined) zDomain = Z;
zDomain = new d3.InternSet(zDomain);
// Omit any data not present in the z-domain.
const I = d3.range(X.length).filter(i => zDomain.has(Z[i]));
// Construct scales and axes.
const xScale = xType(xDomain, xRange);
const yScale = yType(yDomain, yRange);
const xAxis = d3.axisBottom(xScale).ticks(width / 80).tickSizeOuter(0);
const yAxis = d3.axisLeft(yScale).ticks(height / 60, yFormat);
// Compute titles.
const T = title === undefined ? Z : title === null ? null : d3.map(data, title);
// Construct a line generator.
const line = d3.line()
.defined(i => D[i])
.curve(curve)
.x(i => xScale(X[i]))
.y(i => yScale(Y[i]));
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;")
.style("-webkit-tap-highlight-color", "transparent")
.on("pointerenter", pointerentered)
.on("pointermove", pointermoved)
.on("pointerleave", pointerleft)
.on("touchstart", event => event.preventDefault());
// An optional Voronoi display (for fun).
if (voronoi) svg.append("path")
.attr("fill", "none")
.attr("stroke", "#ccc")
.attr("d", d3.Delaunay
.from(I, i => xScale(X[i]), i => yScale(Y[i]))
.voronoi([0, 0, width, height])
.render());
svg.append("g")
.attr("transform", `translate(0,${height - marginBottom})`)
.call(xAxis);
svg.append("g")
.attr("transform", `translate(${marginLeft},0)`)
.call(yAxis)
.call(g => g.select(".domain").remove())
.call(voronoi ? () => {} : 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 path = svg.append("g")
.attr("fill", "none")
.attr("stroke", typeof color === "string" ? color : null)
.attr("stroke-linecap", strokeLinecap)
.attr("stroke-linejoin", strokeLinejoin)
.attr("stroke-width", strokeWidth)
.attr("stroke-opacity", strokeOpacity)
.selectAll("path")
.data(d3.group(I, i => Z[i]))
.join("path")
.style("mix-blend-mode", mixBlendMode)
.attr("stroke", typeof color === "function" ? ([z]) => color(z) : null)
.attr("d", ([, I]) => line(I));
const dot = svg.append("g")
.attr("display", "none");
dot.append("circle")
.attr("r", 2.5);
dot.append("text")
.attr("font-family", "sans-serif")
.attr("font-size", 10)
.attr("text-anchor", "middle")
.attr("y", -8);
function pointermoved(event) {
const [xm, ym] = d3.pointer(event);
const i = d3.least(I, i => Math.hypot(xScale(X[i]) - xm, yScale(Y[i]) - ym)); // closest point
path.style("stroke", ([z]) => Z[i] === z ? null : "#ddd").filter(([z]) => Z[i] === z).raise();
dot.attr("transform", `translate(${xScale(X[i])},${yScale(Y[i])})`);
if (T) dot.select("text").text(T[i]);
svg.property("value", O[i]).dispatch("input", {bubbles: true});
}
function pointerentered() {
path.style("mix-blend-mode", null).style("stroke", "#ddd");
dot.attr("display", null);
}
function pointerleft() {
path.style("mix-blend-mode", mixBlendMode).style("stroke", null);
dot.attr("display", "none");
svg.node().value = null;
svg.dispatch("input", {bubbles: true});
}
return Object.assign(svg.node(), {value: null});
}
import {howto, altplot} from "@d3/example-components"
Purpose-built for displays of data
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.
