105 lines
2.3 KiB
Java
105 lines
2.3 KiB
Java
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/**
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* @fileOverview 使用pow进行度量计算
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* @author dxq613@gmail.com
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*/
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const Base = require('./base');
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const Linear = require('./linear');
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// 求以a为次幂，结果为b的基数，如 x^^a = b;求x
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function calBase(a, b) {
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const e = Math.E;
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const value = Math.pow(e, Math.log(b) / a); // 使用换底公式求底
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return value;
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}
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/**
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* 度量的Pow计算
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* @class Scale.Log
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*/
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class Pow extends Linear {
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_initDefaultCfg() {
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super._initDefaultCfg();
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this.type = 'pow';
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/**
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* @override
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* pow 的坐标点的个数控制在10个以下
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* @type {Number}
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*/
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this.tickCount = 10;
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/**
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* 进行pow计算的基数
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* @type {Number}
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*/
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this.exponent = 2;
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}
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/**
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* @override
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*/
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calculateTicks() {
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const self = this;
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const exponent = self.exponent;
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let min;
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let max = Math.ceil(calBase(exponent, self.max));
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if (self.min >= 0) {
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min = Math.floor(calBase(exponent, self.min));
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} else {
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min = 0;
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}
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if (min > max) {
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const tmp = max;
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max = min;
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min = tmp;
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}
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const count = max - min;
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const tickCount = self.tickCount;
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const avg = Math.ceil(count / tickCount);
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const ticks = [];
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for (let i = min; i < max + avg; i = i + avg) {
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ticks.push(Math.pow(i, exponent));
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}
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return ticks;
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}
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// 获取度量计算时，value占的定义域百分比
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_getScalePercent(value) {
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const max = this.max;
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const min = this.min;
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if (max === min) {
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return 0;
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}
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const exponent = this.exponent;
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const percent = (calBase(exponent, value) - calBase(exponent, min)) / (calBase(exponent, max) - calBase(exponent, min));
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return percent;
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}
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/**
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* @override
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*/
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scale(value) {
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const percent = this._getScalePercent(value);
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const rangeMin = this.rangeMin();
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const rangeMax = this.rangeMax();
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return rangeMin + percent * (rangeMax - rangeMin);
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}
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/**
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* @override
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*/
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invert(value) {
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const percent = (value - this.rangeMin()) / (this.rangeMax() - this.rangeMin());
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const exponent = this.exponent;
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const max = calBase(exponent, this.max);
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const min = calBase(exponent, this.min);
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const tmp = percent * (max - min) + min;
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return Math.pow(tmp, exponent);
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}
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}
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Base.Pow = Pow;
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module.exports = Pow;
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