Published unlisted
Edited
May 3, 2020
data = fetch(
"https://raw.githubusercontent.com/vega/vega/master/docs/data/annual-precip.json"
).then(d => d.json())
{
const svg = d3.create("svg").attr("viewBox", [0, 0, 960, 600]);
const path = d3.geoPath(projection);
yield svg.node();
svg
.append("g")
.selectAll("path")
.data(contours)
.join("path")
.attr("d", path)
.attr("fill", d => color(d.value));
svg
.append("g")
.append("path")
.datum(land)
.attr("fill", "none")
.attr("stroke", "black")
.attr("stroke-width", .5)
.attr("d", path);
}
projection = d3.geoAzimuthalEqualArea().rotate([-180, 243, 178])
contours = d3
.contours()
.thresholds(10)
.size([data.width, data.height])(data.values.map(d => Math.min(3000, d)))
.map(d => Object.assign({ value: d.value }, invert(d)))
function invert(d) {
const n = data.width,
m = data.height;
const shared = {};
let p = {
type: "Polygon",
coordinates: d3.merge(
d.coordinates.map(polygon => {
return polygon.map(ring => {
return ring
.map(point => {
point[0] *= data.scale[0];
point[1] *= data.scale[1];
point[0] += data.translate[0];
point[1] += data.translate[1];
return point;
})
.reverse();
});
})
)
};
// Record the y-intersections with the antimeridian.
p.coordinates.forEach(ring => {
ring.forEach(p => {
if (p[0] === -180) shared[p[1]] |= 1;
else if (p[0] === 180) shared[p[1]] |= 2;
});
});
// Offset any unshared antimeridian points to prevent their stitching.
p.coordinates.forEach(ring => {
ring.forEach(p => {
if ((p[0] === -180 || p[0] === 180) && shared[p[1]] !== 3) {
p[0] = p[0] === -180 ? -179.9995 : 179.9995;
}
});
});
p = d3.geoStitch(p);
// If the MultiPolygon is empty, treat it as the Sphere.
return p.coordinates.length
? { type: "Polygon", coordinates: p.coordinates }
: { type: "Sphere" };
}
color = d3.scaleSequential(d3.interpolateBuPu).domain([0, 3000])
d3 = require("d3@5", "d3-geo-projection@2")
land = fetch(
"https://unpkg.com/visionscarto-world-atlas@0.0.6/world/110m_land.geojson"
).then(d => d.json())
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