Minetrack/assets/js/scale.js

export class RelativeScale {
  static scale(data, tickCount, maxFactor) {
    const { min, max } = RelativeScale.calculateBounds(data);

    let factor = 1;

    while (true) {
      const scale = Math.pow(10, factor);

      const scaledMin = min - (min % scale);
      let scaledMax = max + (max % scale === 0 ? 0 : scale - (max % scale));

      // Prevent min/max from being equal (and generating 0 ticks)
      // This happens when all data points are products of scale value
      if (scaledMin === scaledMax) {
        scaledMax += scale;
      }

      const ticks = (scaledMax - scaledMin) / scale;

      if (
        ticks <= tickCount ||
        (typeof maxFactor === "number" && factor === maxFactor)
      ) {
        return {
          scaledMin,
          scaledMax,
          scale,
        };
      } else {
        // Too many steps between min/max, increase factor and try again
        factor++;
      }
    }
  }

  static scaleMatrix(data, tickCount, maxFactor) {
    const nonNullData = data.flat().filter((val) => val !== null);

    // when used with the spread operator large nonNullData/data arrays can reach the max call stack size
    // use reduce calls to safely determine min/max values for any size of array
    // https://stackoverflow.com/questions/63705432/maximum-call-stack-size-exceeded-when-using-the-dots-operator/63706516#63706516
    const max = nonNullData.reduce((a, b) => {
      return Math.max(a, b);
    }, Number.NEGATIVE_INFINITY);

    return RelativeScale.scale(
      [0, RelativeScale.isFiniteOrZero(max)],
      tickCount,
      maxFactor
    );
  }

  static generateTicks(min, max, step) {
    const ticks = [];
    for (let i = min; i <= max; i += step) {
      ticks.push(i);
    }
    return ticks;
  }

  static calculateBounds(data) {
    if (data.length === 0) {
      return {
        min: 0,
        max: 0,
      };
    } else {
      const nonNullData = data.filter((val) => val !== null);

      // when used with the spread operator large nonNullData/data arrays can reach the max call stack size
      // use reduce calls to safely determine min/max values for any size of array
      // https://stackoverflow.com/questions/63705432/maximum-call-stack-size-exceeded-when-using-the-dots-operator/63706516#63706516
      const min = nonNullData.reduce((a, b) => {
        return Math.min(a, b);
      }, Number.POSITIVE_INFINITY);
      const max = nonNullData.reduce((a, b) => {
        return Math.max(a, b);
      }, Number.NEGATIVE_INFINITY);

      return {
        min: RelativeScale.isFiniteOrZero(min),
        max: RelativeScale.isFiniteOrZero(max),
      };
    }
  }

  static isFiniteOrZero(val) {
    return Number.isFinite(val) ? val : 0;
  }
}