@antv/scale/src/utils/d3-linear-nice.ts

Toolkit for mapping abstract data into visual representation.

// 参考 d3-ticks nice 的实现
// https://github.com/d3/d3-scale

import { tickIncrement } from './ticks';
import { NiceMethod } from '../types';

export const d3LinearNice: NiceMethod = (min: number, max: number, count: number = 5) => {
  const d = [min, max];
  let i0 = 0;
  let i1 = d.length - 1;
  let start = d[i0];
  let stop = d[i1];
  let step;

  if (stop < start) {
    [start, stop] = [stop, start];
    [i0, i1] = [i1, i0];
  }
  step = tickIncrement(start, stop, count);

  if (step > 0) {
    start = Math.floor(start / step) * step;
    stop = Math.ceil(stop / step) * step;
    step = tickIncrement(start, stop, count);
  } else if (step < 0) {
    start = Math.ceil(start * step) / step;
    stop = Math.floor(stop * step) / step;
    step = tickIncrement(start, stop, count);
  }

  if (step > 0) {
    d[i0] = Math.floor(start / step) * step;
    d[i1] = Math.ceil(stop / step) * step;
  } else if (step < 0) {
    d[i0] = Math.ceil(start * step) / step;
    d[i1] = Math.floor(stop * step) / step;
  }
  return d;
};