56 lines
1.9 KiB
JavaScript
56 lines
1.9 KiB
JavaScript
const e10 = Math.sqrt(50),
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e5 = Math.sqrt(10),
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e2 = Math.sqrt(2);
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function tickSpec(start, stop, count) {
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const step = (stop - start) / Math.max(0, count),
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power = Math.floor(Math.log10(step)),
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error = step / Math.pow(10, power),
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factor = error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1;
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let i1, i2, inc;
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if (power < 0) {
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inc = Math.pow(10, -power) / factor;
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i1 = Math.round(start * inc);
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i2 = Math.round(stop * inc);
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if (i1 / inc < start) ++i1;
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if (i2 / inc > stop) --i2;
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inc = -inc;
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} else {
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inc = Math.pow(10, power) * factor;
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i1 = Math.round(start / inc);
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i2 = Math.round(stop / inc);
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if (i1 * inc < start) ++i1;
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if (i2 * inc > stop) --i2;
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}
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if (i2 < i1 && 0.5 <= count && count < 2) return tickSpec(start, stop, count * 2);
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return [i1, i2, inc];
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}
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export default function ticks(start, stop, count) {
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stop = +stop, start = +start, count = +count;
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if (!(count > 0)) return [];
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if (start === stop) return [start];
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const reverse = stop < start, [i1, i2, inc] = reverse ? tickSpec(stop, start, count) : tickSpec(start, stop, count);
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if (!(i2 >= i1)) return [];
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const n = i2 - i1 + 1, ticks = new Array(n);
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if (reverse) {
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if (inc < 0) for (let i = 0; i < n; ++i) ticks[i] = (i2 - i) / -inc;
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else for (let i = 0; i < n; ++i) ticks[i] = (i2 - i) * inc;
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} else {
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if (inc < 0) for (let i = 0; i < n; ++i) ticks[i] = (i1 + i) / -inc;
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else for (let i = 0; i < n; ++i) ticks[i] = (i1 + i) * inc;
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}
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return ticks;
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}
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export function tickIncrement(start, stop, count) {
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stop = +stop, start = +start, count = +count;
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return tickSpec(start, stop, count)[2];
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}
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export function tickStep(start, stop, count) {
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stop = +stop, start = +start, count = +count;
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const reverse = stop < start, inc = reverse ? tickIncrement(stop, start, count) : tickIncrement(start, stop, count);
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return (reverse ? -1 : 1) * (inc < 0 ? 1 / -inc : inc);
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}
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