dd_xcx/node_modules/@antv/scale/lib/log.js

function _inheritsLoose(subClass, superClass) { subClass.prototype = Object.create(superClass.prototype); subClass.prototype.constructor = subClass; subClass.__proto__ = superClass; }

/**
 * @fileOverview 使用度量，进行log转换
 * @author dxq613@gmail.com
 */
var each = require('@antv/util/lib/each');

var Base = require('./base');

var Linear = require('./linear'); // 计算log


function log(a, b) {
  if (a === 1) {
    return 1;
  }

  return Math.log(b) / Math.log(a);
}
/**
 * 度量的log计算
 * @class Scale.Log
 */


var Log =
/*#__PURE__*/
function (_Linear) {
  _inheritsLoose(Log, _Linear);

  function Log() {
    return _Linear.apply(this, arguments) || this;
  }

  var _proto = Log.prototype;

  _proto._initDefaultCfg = function _initDefaultCfg() {
    _Linear.prototype._initDefaultCfg.call(this);

    this.type = 'log';
    /**
     * @override
     * log 的坐标点的个数控制在10个以下
     * @type {Number}
     */

    this.tickCount = 10;
    /**
     * 进行log计算的基数
     * @type {Number}
     */

    this.base = 2; // 最小的tick，仅内部使用

    this._minTick = null;
  }
  /**
   * @override
   */
  ;

  _proto.calculateTicks = function calculateTicks() {
    var self = this;
    var base = self.base;
    var minTick;

    if (self.min < 0) {
      throw new Error('The minimum value must be greater than zero!');
    }

    var maxTick = log(base, self.max);

    if (self.min > 0) {
      minTick = Math.floor(log(base, self.min));
    } else {
      var values = self.values;
      var positiveMin = self.max; // 查找大于0的第一个值, 如果都小于0，默认为1

      each(values, function (value) {
        if (value > 0 && value < positiveMin) {
          positiveMin = value;
        }
      });

      if (positiveMin === self.max) {
        positiveMin = self.max / base;
      }

      if (positiveMin > 1) {
        positiveMin = 1;
      }

      minTick = Math.floor(log(base, positiveMin));
      self._minTick = minTick;
      self.positiveMin = positiveMin;
    }

    var count = maxTick - minTick;
    var tickCount = self.tickCount;
    var avg = Math.ceil(count / tickCount);
    var ticks = [];

    for (var i = minTick; i < maxTick + avg; i = i + avg) {
      ticks.push(Math.pow(base, i));
    }

    if (self.min === 0) {
      ticks.unshift(0);
    }

    return ticks;
  } // 获取度量计算时，value占的定义域百分比
  ;

  _proto._getScalePercent = function _getScalePercent(value) {
    var max = this.max;
    var min = this.min;

    if (max === min) {
      return 0;
    } // 如果值小于等于0，则按照0处理


    if (value <= 0) {
      return 0;
    }

    var base = this.base;
    var positiveMin = this.positiveMin; // 如果min == 0, 则根据比0大的最小值，计算比例关系。这个最小值作为坐标轴上的第二个tick，第一个是0但是不显示

    if (positiveMin) {
      min = positiveMin * 1 / base;
    }

    var percent; // 如果数值小于次小值，那么就计算 value / 次小值 占整体的比例

    if (value < positiveMin) {
      percent = value / positiveMin / (log(base, max) - log(base, min));
    } else {
      percent = (log(base, value) - log(base, min)) / (log(base, max) - log(base, min));
    }

    return percent;
  }
  /**
   * @override
   */
  ;

  _proto.scale = function scale(value) {
    var percent = this._getScalePercent(value);

    var rangeMin = this.rangeMin();
    var rangeMax = this.rangeMax();
    return rangeMin + percent * (rangeMax - rangeMin);
  }
  /**
   * @override
   */
  ;

  _proto.invert = function invert(value) {
    var base = this.base;
    var max = log(base, this.max);
    var rangeMin = this.rangeMin();
    var range = this.rangeMax() - rangeMin;
    var min;
    var positiveMin = this.positiveMin;

    if (positiveMin) {
      if (value === 0) {
        return 0;
      }

      min = log(base, positiveMin / base);
      var appendPercent = 1 / (max - min) * range; // 0 到 positiveMin的占比

      if (value < appendPercent) {
        // 落到 0 - positiveMin 之间
        return value / appendPercent * positiveMin;
      }
    } else {
      min = log(base, this.min);
    }

    var percent = (value - rangeMin) / range;
    var tmp = percent * (max - min) + min;
    return Math.pow(base, tmp);
  };

  return Log;
}(Linear);

Base.Log = Log;
module.exports = Log;