diff --git a/src/ticks.js b/src/ticks.js index 6ce6977..5868d8d 100644 --- a/src/ticks.js +++ b/src/ticks.js @@ -1,54 +1,55 @@ -var e10 = Math.sqrt(50), +const e10 = Math.sqrt(50), e5 = Math.sqrt(10), e2 = Math.sqrt(2); -export default function ticks(start, stop, count) { - var reverse, - i = -1, - n, - ticks, - step; +function tickSpec(start, stop, count) { + const step = (stop - start) / Math.max(0, count), + power = Math.floor(Math.log10(step)), + error = step / Math.pow(10, power), + factor = error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1; + let i1, i2, inc; + if (power < 0) { + inc = Math.pow(10, -power) / factor; + i1 = Math.round(start * inc); + i2 = Math.round(stop * inc); + if (i1 / inc < start) ++i1; + if (i2 / inc > stop) --i2; + inc = -inc; + } else { + inc = Math.pow(10, power) * factor; + i1 = Math.round(start / inc); + i2 = Math.round(stop / inc); + if (i1 * inc < start) ++i1; + if (i2 * inc > stop) --i2; + } + if (i2 < i1 && 0.5 <= count && count < 2) return tickSpec(start, stop, count * 2); + return [i1, i2, inc]; +} +export default function ticks(start, stop, count) { stop = +stop, start = +start, count = +count; - if (start === stop && count > 0) return [start]; - if (reverse = stop < start) n = start, start = stop, stop = n; - if ((step = tickIncrement(start, stop, count)) === 0 || !isFinite(step)) return []; - - if (step > 0) { - let r0 = Math.round(start / step), r1 = Math.round(stop / step); - if (r0 * step < start) ++r0; - if (r1 * step > stop) --r1; - ticks = new Array(n = r1 - r0 + 1); - while (++i < n) ticks[i] = (r0 + i) * step; + if (!(count > 0)) return []; + if (start === stop) return [start]; + const reverse = stop < start, [i1, i2, inc] = reverse ? tickSpec(stop, start, count) : tickSpec(start, stop, count); + if (!(i2 >= i1)) return []; + const n = i2 - i1 + 1, ticks = new Array(n); + if (reverse) { + if (inc < 0) for (let i = 0; i < n; ++i) ticks[i] = (i2 - i) / -inc; + else for (let i = 0; i < n; ++i) ticks[i] = (i2 - i) * inc; } else { - step = -step; - let r0 = Math.round(start * step), r1 = Math.round(stop * step); - if (r0 / step < start) ++r0; - if (r1 / step > stop) --r1; - ticks = new Array(n = r1 - r0 + 1); - while (++i < n) ticks[i] = (r0 + i) / step; + if (inc < 0) for (let i = 0; i < n; ++i) ticks[i] = (i1 + i) / -inc; + else for (let i = 0; i < n; ++i) ticks[i] = (i1 + i) * inc; } - - if (reverse) ticks.reverse(); - return ticks; } export function tickIncrement(start, stop, count) { - var step = (stop - start) / Math.max(0, count), - power = Math.floor(Math.log(step) / Math.LN10), - error = step / Math.pow(10, power); - return power >= 0 - ? (error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1) * Math.pow(10, power) - : -Math.pow(10, -power) / (error >= e10 ? 10 : error >= e5 ? 5 : error >= e2 ? 2 : 1); + stop = +stop, start = +start, count = +count; + return tickSpec(start, stop, count)[2]; } export function tickStep(start, stop, count) { - var step0 = Math.abs(stop - start) / Math.max(0, count), - step1 = Math.pow(10, Math.floor(Math.log(step0) / Math.LN10)), - error = step0 / step1; - if (error >= e10) step1 *= 10; - else if (error >= e5) step1 *= 5; - else if (error >= e2) step1 *= 2; - return stop < start ? -step1 : step1; + stop = +stop, start = +start, count = +count; + const reverse = stop < start, inc = reverse ? tickIncrement(stop, start, count) : tickIncrement(start, stop, count); + return (reverse ? -1 : 1) * (inc < 0 ? 1 / -inc : inc); } diff --git a/test/ticks-test.js b/test/ticks-test.js index 3b4fd98..4793e65 100644 --- a/test/ticks-test.js +++ b/test/ticks-test.js @@ -109,3 +109,19 @@ it("ticks(start, stop, count) returns the reverse of ticks(stop, start, count)", it("ticks(start, stop, count) handles precision problems", () => { assert.deepStrictEqual(ticks(0.98, 1.14, 10), [0.98, 1, 1.02, 1.04, 1.06, 1.08, 1.1, 1.12, 1.14]); }); + +it("ticks(start, stop, count) tries to return at least one tick if count >= 0.5", () => { + assert.deepStrictEqual(ticks(1, 364, 0.1), []); + assert.deepStrictEqual(ticks(1, 364, 0.499), []); + assert.deepStrictEqual(ticks(1, 364, 0.5), [200]); + assert.deepStrictEqual(ticks(1, 364, 1), [200]); + assert.deepStrictEqual(ticks(1, 364, 1.5), [200]); + assert.deepStrictEqual(ticks(1, 499, 1), [200, 400]); + assert.deepStrictEqual(ticks(364, 1, 0.5), [200]); + assert.deepStrictEqual(ticks(0.001, 0.364, 0.5), [0.2]); + assert.deepStrictEqual(ticks(0.364, 0.001, 0.5), [0.2]); + assert.deepStrictEqual(ticks(-1, -364, 0.5), [-200]); + assert.deepStrictEqual(ticks(-364, -1, 0.5), [-200]); + assert.deepStrictEqual(ticks(-0.001, -0.364, 0.5), [-0.2]); + assert.deepStrictEqual(ticks(-0.364, -0.001, 0.5), [-0.2]); +});