@antv/scale/src/scales/quantile.ts

Toolkit for mapping abstract data into visual representation.

import { Threshold } from './threshold';
import { QuantileOptions, Range } from '../types';
import { wilkinsonExtended } from '../tick-methods/wilkinson-extended';
import { createQuartile } from '../utils/create-quartile';

/**
 * 类似 Threshold 比例尺，区别在于分位数比例尺 (Quantile) 将一个离散的输入域映射到一个离散的输出域
 * 输入域被指定为一组离散的样本值，输出域中的值的数量决定了分位数的数量。
 */
export class Quantile extends Threshold<QuantileOptions> {
  protected getDefaultOptions(): QuantileOptions {
    return {
      domain: [],
      range: [],
      tickCount: 5,
      unknown: undefined,
      tickMethod: wilkinsonExtended,
    };
  }

  constructor(options?: QuantileOptions) {
    super(options);
  }

  protected rescale() {
    const { domain, range } = this.options;

    this.n = range.length - 1;
    this.thresholds = createQuartile(domain, this.n + 1, false);
  }

  /**
   * 如果是在第一段后或者最后一段就把两端的值添加上
   */
  public invert(y: Range<QuantileOptions>) {
    const [a, b] = super.invert(y);
    const { domain } = this.options;
    const dMin = domain[0];
    const dMax = domain[domain.length - 1];
    return a === undefined && b === undefined ? [a, b] : [a || dMin, b || dMax];
  }

  public getThresholds() {
    return this.thresholds;
  }

  public clone() {
    return new Quantile(this.options);
  }

  public getTicks() {
    const { tickCount, domain, tickMethod } = this.options;

    const lastIndex = domain.length - 1;
    const min = domain[0];
    const max = domain[lastIndex];
    return tickMethod(min, max, tickCount);
  }
}