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Sankey diagram
chart = {
// Specify the dimensions of the chart.
const width = 928;
const height = 600;
const format = d3.format(",.0f");
// Create a SVG container.
const svg = d3.create("svg")
.attr("width", width)
.attr("height", height)
.attr("viewBox", [0, 0, width, height])
.attr("style", "max-width: 100%; height: auto; font: 10px sans-serif;");
// Constructs and configures a Sankey generator.
const sankey = d3.sankey()
.nodeId(d => d.name)
.nodeAlign(d3[nodeAlign]) // d3.sankeyLeft, etc.
.nodeWidth(15)
.nodePadding(10)
.extent([[1, 5], [width - 1, height - 5]]);
// Applies it to the data. We make a copy of the nodes and links objects
// so as to avoid mutating the original.
const {nodes, links} = sankey({
nodes: data.nodes.map(d => Object.assign({}, d)),
links: data.links.map(d => Object.assign({}, d))
});
// Defines a color scale.
const color = d3.scaleOrdinal(d3.schemeCategory10);
// Creates the rects that represent the nodes.
const rect = svg.append("g")
.attr("stroke", "#000")
.selectAll()
.data(nodes)
.join("rect")
.attr("x", d => d.x0)
.attr("y", d => d.y0)
.attr("height", d => d.y1 - d.y0)
.attr("width", d => d.x1 - d.x0)
.attr("fill", d => color(d.category));
// Adds a title on the nodes.
rect.append("title")
.text(d => `${d.name}\n${format(d.value)} TWh`);
// Creates the paths that represent the links.
const link = svg.append("g")
.attr("fill", "none")
.attr("stroke-opacity", 0.5)
.selectAll()
.data(links)
.join("g")
.style("mix-blend-mode", "multiply");
// Creates a gradient, if necessary, for the source-target color option.
if (linkColor === "source-target") {
const gradient = link.append("linearGradient")
.attr("id", d => (d.uid = DOM.uid("link")).id)
.attr("gradientUnits", "userSpaceOnUse")
.attr("x1", d => d.source.x1)
.attr("x2", d => d.target.x0);
gradient.append("stop")
.attr("offset", "0%")
.attr("stop-color", d => color(d.source.category));
gradient.append("stop")
.attr("offset", "100%")
.attr("stop-color", d => color(d.target.category));
}
link.append("path")
.attr("d", d3.sankeyLinkHorizontal())
.attr("stroke", linkColor === "source-target" ? (d) => d.uid
: linkColor === "source" ? (d) => color(d.source.category)
: linkColor === "target" ? (d) => color(d.target.category)
: linkColor)
.attr("stroke-width", d => Math.max(1, d.width));
link.append("title")
.text(d => `${d.source.name} → ${d.target.name}\n${format(d.value)} TWh`);
// Adds labels on the nodes.
svg.append("g")
.selectAll()
.data(nodes)
.join("text")
.attr("x", d => d.x0 < width / 2 ? d.x1 + 6 : d.x0 - 6)
.attr("y", d => (d.y1 + d.y0) / 2)
.attr("dy", "0.35em")
.attr("text-anchor", d => d.x0 < width / 2 ? "start" : "end")
.text(d => d.name);
return svg.node();
}
data = {
const links = await FileAttachment("energy.csv").csv({typed: true});
const nodes = Array.from(new Set(links.flatMap(l => [l.source, l.target])), name => ({name, category: name.replace(/ .*/, "")}));
return {nodes, links};
}
// [d3-sankey](https://github.com/d3/d3-sankey) is not part of the D3 bundle
d3 = require("d3@7", "d3-sankey@0.12")
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.
