時系列データの累積和

cumulativeSumObjects.ts

/**
 * cumulativeSumObjects({
 *   20200101: {a: 1, b: 2, c: 3},
 *   20200102: {b: 1, c: 2, d: 3},
 *   20200103: {c: 1, d: 2, e: 3},
 * })
 * => {
 *   20200101: {a: 1, b: 2, c: 3, d: 0, e: 0},
 *   20200102: {a: 1, b: 3, c: 5, d: 3, e: 0},
 *   20200103: {a: 1, b: 3, c: 6, d: 5, e: 3},
 * }
 */
type SeriesItem = Record<string, number>
type SeriesObjects = Record<string, SeriesItem>

const cumulativeSumObjects = (seriesData: SeriesObjects) => {
  const baseRecord = Object.values(seriesData).reduce((acc, cur) => {
    Object.keys(cur).forEach((k) => (acc[k] = 0))
    return acc
  }, {})

  const sumObjects = (objects: SeriesItem[]) =>
    objects.reduce(
      (acc, cur) => {
        Object.entries(cur).forEach(([k, v]) => {
          acc[k] = (acc[k] ?? 0) + v
        })
        return acc
      },
      { ...baseRecord }
    )

  return Object.entries(seriesData).reduce((acc: SeriesObjects, [k], i) => {
    const targets = Object.values(seriesData).filter((_, _i) => _i <= i)
    acc[k] = sumObjects(targets)
    return acc
  }, {})
}