Function createLinearScale

src/utils/scales.ts:84–135

()

 * domain [0, 1] -> range [0, 1]
 */
export function createLinearScale(): LinearScale {
  let domainMin = 0;
  let domainMax = 1;
  let rangeMin = 0;
  let rangeMax = 1;

  const self: LinearScale = {
    domain(min: number, max: number) {
      assertFinite('domain min', min);
      assertFinite('domain max', max);
      domainMin = min;
      domainMax = max;
      return self;
    },

    range(min: number, max: number) {
      assertFinite('range min', min);
      assertFinite('range max', max);
      rangeMin = min;
      rangeMax = max;
      return self;
    },

    scale(value: number) {
      if (!Number.isFinite(value)) return Number.NaN;

      if (domainMin === domainMax) {
        return (rangeMin + rangeMax) / 2;
      }

      const t = (value - domainMin) / (domainMax - domainMin);
      return rangeMin + t * (rangeMax - rangeMin);
    },

    invert(pixel: number) {
      if (!Number.isFinite(pixel)) return Number.NaN;

      if (domainMin === domainMax) {
        return domainMin;
      }

      if (rangeMin === rangeMax) {
        return (domainMin + domainMax) / 2;
      }

      const t = (pixel - rangeMin) / (rangeMax - rangeMin);
      return domainMin + t * (domainMax - domainMin);
    },
  };

  return self;
}

/**
 * Creates a category scale for mapping string categories to evenly spaced