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114 lines
3.8 KiB
JavaScript
114 lines
3.8 KiB
JavaScript
// Copyright 2021 Observable, Inc.
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// Released under the ISC license.
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// https://observablehq.com/@d3/choropleth
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function Choropleth({
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id = d => d.id, // given d in data, returns the feature id
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value = () => undefined, // given d in data, returns the quantitative value
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title, // given a feature f and possibly a datum d, returns the hover text
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format, // optional format specifier for the title
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scale = d3.scaleSequential, // type of color scale
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domain, // [min, max] values; input of color scale
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range = d3.interpolateBlues, // output of color scale
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width = 640, // outer width, in pixels
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height, // outer height, in pixels
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projection, // a D3 projection; null for pre-projected geometry
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features, // a GeoJSON feature collection
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featureId = d => d.id, // given a feature, returns its id
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borders, // a GeoJSON object for stroking borders
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outline = projection && projection.rotate ? {type: "Sphere"} : null, // a GeoJSON object for the background
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unknown = "#ccc", // fill color for missing data
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fill = "white", // fill color for outline
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stroke = "white", // stroke color for borders
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strokeLinecap = "round", // stroke line cap for borders
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strokeLinejoin = "round", // stroke line join for borders
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strokeWidth, // stroke width for borders
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strokeOpacity, // stroke opacity for borders
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duration = 0, // duration for transitions
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} = {}) {
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// Compute feture map
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const If = d3.map(features.features, featureId);
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// Compute the default height. If an outline object is specified, scale the projection to fit
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// the width, and then compute the corresponding height.
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if (height === undefined) {
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if (outline === undefined) {
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height = 400;
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} else {
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const [[x0, y0], [x1, y1]] = d3.geoPath(projection.fitWidth(width, outline)).bounds(outline);
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const dy = Math.ceil(y1 - y0), l = Math.min(Math.ceil(x1 - x0), dy);
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projection.scale(projection.scale() * (l - 1) / l).precision(0.2);
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height = dy;
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}
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}
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// Construct a path generator.
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const path = d3.geoPath(projection);
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// Update DOM
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const svg = d3.create("svg")
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.classed('choropleth', true)
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.attr("width", width)
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.attr("height", height)
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.attr("viewBox", [0, 0, width, height])
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.attr("style", "width: 100%; height: auto; height: intrinsic;");
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svg.append("g")
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.classed("data-group", true);
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if (outline != null) svg.append("path")
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.classed('hidden', false)
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.attr("fill", fill)
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.attr("stroke", "currentColor")
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.attr("d", path(outline));
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if (borders != null) svg.append("path")
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.attr("pointer-events", "none")
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.attr("fill", "none")
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.attr("stroke", stroke)
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.attr("stroke-linecap", strokeLinecap)
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.attr("stroke-linejoin", strokeLinejoin)
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.attr("stroke-width", strokeWidth)
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.attr("stroke-opacity", strokeOpacity)
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.attr("d", path(borders));
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// Object facet to update visualization
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let obj = {
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node: svg.node(),
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update: function (data) {
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const dataDomain = domain(data);
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const color = scale(dataDomain, range);
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if (color.unknown && unknown !== undefined) color.unknown(unknown);
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// Update DOM
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const svg = d3.select("svg.choropleth");
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svg.select("g.data-group")
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.selectAll("path")
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.data(features.features)
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.join(
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(enter) => {
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return enter.append("path")
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.attr("fill",
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(d, i) => color(value(data[d.id])))
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.attr("d", path)
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.append("title")
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.text((d, i) => title(d, data[d.id]));
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},
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(update) => {
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update
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.transition()
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.duration(duration)
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.attr("fill", (d, i) =>
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color(data[d.id].sevenDayMean));
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return update
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.select("title")
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.text((d, i) => title(d, data[d.id]));
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});
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Object.assign(svg.node(), {scales: {color}});
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}
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}
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return obj;
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}
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