public/zh/builder/src/echarts/scale/Log.js

/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements.  See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership.  The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License.  You may obtain a copy of the License at
*
*   http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied.  See the License for the
* specific language governing permissions and limitations
* under the License.
*/

/**
 * Log scale
 * @module echarts/scale/Log
 */
import * as zrUtil from 'zrender/src/core/util';
import Scale from './Scale';
import * as numberUtil from '../util/number'; // Use some method of IntervalScale

import IntervalScale from './Interval';
var scaleProto = Scale.prototype;
var intervalScaleProto = IntervalScale.prototype;
var getPrecisionSafe = numberUtil.getPrecisionSafe;
var roundingErrorFix = numberUtil.round;
var mathFloor = Math.floor;
var mathCeil = Math.ceil;
var mathPow = Math.pow;
var mathLog = Math.log;
var LogScale = Scale.extend({
  type: 'log',
  base: 10,
  $constructor: function () {
    Scale.apply(this, arguments);
    this._originalScale = new IntervalScale();
  },

  /**
   * @return {Array.<number>}
   */
  getTicks: function () {
    var originalScale = this._originalScale;
    var extent = this._extent;
    var originalExtent = originalScale.getExtent();
    return zrUtil.map(intervalScaleProto.getTicks.call(this), function (val) {
      var powVal = numberUtil.round(mathPow(this.base, val)); // Fix #4158

      powVal = val === extent[0] && originalScale.__fixMin ? fixRoundingError(powVal, originalExtent[0]) : powVal;
      powVal = val === extent[1] && originalScale.__fixMax ? fixRoundingError(powVal, originalExtent[1]) : powVal;
      return powVal;
    }, this);
  },

  /**
   * @param {number} val
   * @return {string}
   */
  getLabel: intervalScaleProto.getLabel,

  /**
   * @param  {number} val
   * @return {number}
   */
  scale: function (val) {
    val = scaleProto.scale.call(this, val);
    return mathPow(this.base, val);
  },

  /**
   * @param {number} start
   * @param {number} end
   */
  setExtent: function (start, end) {
    var base = this.base;
    start = mathLog(start) / mathLog(base);
    end = mathLog(end) / mathLog(base);
    intervalScaleProto.setExtent.call(this, start, end);
  },

  /**
   * @return {number} end
   */
  getExtent: function () {
    var base = this.base;
    var extent = scaleProto.getExtent.call(this);
    extent[0] = mathPow(base, extent[0]);
    extent[1] = mathPow(base, extent[1]); // Fix #4158

    var originalScale = this._originalScale;
    var originalExtent = originalScale.getExtent();
    originalScale.__fixMin && (extent[0] = fixRoundingError(extent[0], originalExtent[0]));
    originalScale.__fixMax && (extent[1] = fixRoundingError(extent[1], originalExtent[1]));
    return extent;
  },

  /**
   * @param  {Array.<number>} extent
   */
  unionExtent: function (extent) {
    this._originalScale.unionExtent(extent);

    var base = this.base;
    extent[0] = mathLog(extent[0]) / mathLog(base);
    extent[1] = mathLog(extent[1]) / mathLog(base);
    scaleProto.unionExtent.call(this, extent);
  },

  /**
   * @override
   */
  unionExtentFromData: function (data, dim) {
    // TODO
    // filter value that <= 0
    this.unionExtent(data.getApproximateExtent(dim));
  },

  /**
   * Update interval and extent of intervals for nice ticks
   * @param  {number} [approxTickNum = 10] Given approx tick number
   */
  niceTicks: function (approxTickNum) {
    approxTickNum = approxTickNum || 10;
    var extent = this._extent;
    var span = extent[1] - extent[0];

    if (span === Infinity || span <= 0) {
      return;
    }

    var interval = numberUtil.quantity(span);
    var err = approxTickNum / span * interval; // Filter ticks to get closer to the desired count.

    if (err <= 0.5) {
      interval *= 10;
    } // Interval should be integer


    while (!isNaN(interval) && Math.abs(interval) < 1 && Math.abs(interval) > 0) {
      interval *= 10;
    }

    var niceExtent = [numberUtil.round(mathCeil(extent[0] / interval) * interval), numberUtil.round(mathFloor(extent[1] / interval) * interval)];
    this._interval = interval;
    this._niceExtent = niceExtent;
  },

  /**
   * Nice extent.
   * @override
   */
  niceExtent: function (opt) {
    intervalScaleProto.niceExtent.call(this, opt);
    var originalScale = this._originalScale;
    originalScale.__fixMin = opt.fixMin;
    originalScale.__fixMax = opt.fixMax;
  }
});
zrUtil.each(['contain', 'normalize'], function (methodName) {
  LogScale.prototype[methodName] = function (val) {
    val = mathLog(val) / mathLog(this.base);
    return scaleProto[methodName].call(this, val);
  };
});

LogScale.create = function () {
  return new LogScale();
};

function fixRoundingError(val, originalVal) {
  return roundingErrorFix(val, getPrecisionSafe(originalVal));
}

export default LogScale;