226 lines
6.8 KiB
JavaScript
226 lines
6.8 KiB
JavaScript
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import {extent, nice, thresholdSturges, ticks} from "d3-array";
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import {slice} from "./array.js";
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import ascending from "./ascending.js";
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import area from "./area.js";
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import constant from "./constant.js";
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import contains from "./contains.js";
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import noop from "./noop.js";
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var cases = [
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[],
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[[[1.0, 1.5], [0.5, 1.0]]],
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[[[1.5, 1.0], [1.0, 1.5]]],
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[[[1.5, 1.0], [0.5, 1.0]]],
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[[[1.0, 0.5], [1.5, 1.0]]],
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[[[1.0, 1.5], [0.5, 1.0]], [[1.0, 0.5], [1.5, 1.0]]],
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[[[1.0, 0.5], [1.0, 1.5]]],
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[[[1.0, 0.5], [0.5, 1.0]]],
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[[[0.5, 1.0], [1.0, 0.5]]],
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[[[1.0, 1.5], [1.0, 0.5]]],
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[[[0.5, 1.0], [1.0, 0.5]], [[1.5, 1.0], [1.0, 1.5]]],
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[[[1.5, 1.0], [1.0, 0.5]]],
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[[[0.5, 1.0], [1.5, 1.0]]],
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[[[1.0, 1.5], [1.5, 1.0]]],
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[[[0.5, 1.0], [1.0, 1.5]]],
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[]
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];
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export default function() {
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var dx = 1,
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dy = 1,
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threshold = thresholdSturges,
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smooth = smoothLinear;
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function contours(values) {
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var tz = threshold(values);
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// Convert number of thresholds into uniform thresholds.
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if (!Array.isArray(tz)) {
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const e = extent(values, finite);
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tz = ticks(...nice(e[0], e[1], tz), tz);
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while (tz[tz.length - 1] >= e[1]) tz.pop();
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while (tz[1] < e[0]) tz.shift();
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} else {
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tz = tz.slice().sort(ascending);
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}
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return tz.map(value => contour(values, value));
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}
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// Accumulate, smooth contour rings, assign holes to exterior rings.
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// Based on https://github.com/mbostock/shapefile/blob/v0.6.2/shp/polygon.js
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function contour(values, value) {
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const v = value == null ? NaN : +value;
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if (isNaN(v)) throw new Error(`invalid value: ${value}`);
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var polygons = [],
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holes = [];
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isorings(values, v, function(ring) {
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smooth(ring, values, v);
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if (area(ring) > 0) polygons.push([ring]);
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else holes.push(ring);
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});
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holes.forEach(function(hole) {
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for (var i = 0, n = polygons.length, polygon; i < n; ++i) {
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if (contains((polygon = polygons[i])[0], hole) !== -1) {
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polygon.push(hole);
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return;
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}
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}
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});
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return {
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type: "MultiPolygon",
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value: value,
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coordinates: polygons
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};
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}
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// Marching squares with isolines stitched into rings.
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// Based on https://github.com/topojson/topojson-client/blob/v3.0.0/src/stitch.js
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function isorings(values, value, callback) {
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var fragmentByStart = new Array,
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fragmentByEnd = new Array,
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x, y, t0, t1, t2, t3;
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// Special case for the first row (y = -1, t2 = t3 = 0).
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x = y = -1;
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t1 = above(values[0], value);
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cases[t1 << 1].forEach(stitch);
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while (++x < dx - 1) {
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t0 = t1, t1 = above(values[x + 1], value);
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cases[t0 | t1 << 1].forEach(stitch);
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}
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cases[t1 << 0].forEach(stitch);
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// General case for the intermediate rows.
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while (++y < dy - 1) {
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x = -1;
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t1 = above(values[y * dx + dx], value);
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t2 = above(values[y * dx], value);
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cases[t1 << 1 | t2 << 2].forEach(stitch);
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while (++x < dx - 1) {
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t0 = t1, t1 = above(values[y * dx + dx + x + 1], value);
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t3 = t2, t2 = above(values[y * dx + x + 1], value);
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cases[t0 | t1 << 1 | t2 << 2 | t3 << 3].forEach(stitch);
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}
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cases[t1 | t2 << 3].forEach(stitch);
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}
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// Special case for the last row (y = dy - 1, t0 = t1 = 0).
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x = -1;
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t2 = values[y * dx] >= value;
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cases[t2 << 2].forEach(stitch);
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while (++x < dx - 1) {
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t3 = t2, t2 = above(values[y * dx + x + 1], value);
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cases[t2 << 2 | t3 << 3].forEach(stitch);
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}
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cases[t2 << 3].forEach(stitch);
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function stitch(line) {
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var start = [line[0][0] + x, line[0][1] + y],
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end = [line[1][0] + x, line[1][1] + y],
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startIndex = index(start),
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endIndex = index(end),
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f, g;
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if (f = fragmentByEnd[startIndex]) {
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if (g = fragmentByStart[endIndex]) {
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delete fragmentByEnd[f.end];
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delete fragmentByStart[g.start];
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if (f === g) {
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f.ring.push(end);
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callback(f.ring);
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} else {
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fragmentByStart[f.start] = fragmentByEnd[g.end] = {start: f.start, end: g.end, ring: f.ring.concat(g.ring)};
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}
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} else {
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delete fragmentByEnd[f.end];
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f.ring.push(end);
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fragmentByEnd[f.end = endIndex] = f;
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}
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} else if (f = fragmentByStart[endIndex]) {
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if (g = fragmentByEnd[startIndex]) {
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delete fragmentByStart[f.start];
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delete fragmentByEnd[g.end];
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if (f === g) {
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f.ring.push(end);
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callback(f.ring);
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} else {
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fragmentByStart[g.start] = fragmentByEnd[f.end] = {start: g.start, end: f.end, ring: g.ring.concat(f.ring)};
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}
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} else {
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delete fragmentByStart[f.start];
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f.ring.unshift(start);
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fragmentByStart[f.start = startIndex] = f;
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}
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} else {
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fragmentByStart[startIndex] = fragmentByEnd[endIndex] = {start: startIndex, end: endIndex, ring: [start, end]};
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}
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}
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}
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function index(point) {
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return point[0] * 2 + point[1] * (dx + 1) * 4;
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}
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function smoothLinear(ring, values, value) {
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ring.forEach(function(point) {
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var x = point[0],
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y = point[1],
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xt = x | 0,
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yt = y | 0,
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v1 = valid(values[yt * dx + xt]);
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if (x > 0 && x < dx && xt === x) {
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point[0] = smooth1(x, valid(values[yt * dx + xt - 1]), v1, value);
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}
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if (y > 0 && y < dy && yt === y) {
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point[1] = smooth1(y, valid(values[(yt - 1) * dx + xt]), v1, value);
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}
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});
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}
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contours.contour = contour;
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contours.size = function(_) {
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if (!arguments.length) return [dx, dy];
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var _0 = Math.floor(_[0]), _1 = Math.floor(_[1]);
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if (!(_0 >= 0 && _1 >= 0)) throw new Error("invalid size");
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return dx = _0, dy = _1, contours;
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};
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contours.thresholds = function(_) {
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return arguments.length ? (threshold = typeof _ === "function" ? _ : Array.isArray(_) ? constant(slice.call(_)) : constant(_), contours) : threshold;
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};
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contours.smooth = function(_) {
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return arguments.length ? (smooth = _ ? smoothLinear : noop, contours) : smooth === smoothLinear;
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};
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return contours;
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}
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// When computing the extent, ignore infinite values (as well as invalid ones).
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function finite(x) {
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return isFinite(x) ? x : NaN;
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}
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// Is the (possibly invalid) x greater than or equal to the (known valid) value?
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// Treat any invalid value as below negative infinity.
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function above(x, value) {
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return x == null ? false : +x >= value;
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}
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// During smoothing, treat any invalid value as negative infinity.
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function valid(v) {
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return v == null || isNaN(v = +v) ? -Infinity : v;
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}
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function smooth1(x, v0, v1, value) {
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const a = value - v0;
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const b = v1 - v0;
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const d = isFinite(a) || isFinite(b) ? a / b : Math.sign(a) / Math.sign(b);
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return isNaN(d) ? x : x + d - 0.5;
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}
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