Function stack

src/utils/stackingUtils.ts:65–110

(
  datasets: Dataset[],
  keyAccessor: IAccessor<any>,
  valueAccessor: IAccessor<number>,
  stackingOrder: IStackingOrder = "bottomup",
)

 * @return {StackingResult} value and offset for each datapoint in each Dataset
 */
export function stack(
  datasets: Dataset[],
  keyAccessor: IAccessor<any>,
  valueAccessor: IAccessor<number>,
  stackingOrder: IStackingOrder = "bottomup",
): StackingResult {
  const positiveOffsets = d3.map<number>();
  const negativeOffsets = d3.map<number>();
  const datasetToKeyToStackedDatum = new Utils.Map<Dataset, Utils.Map<string, StackedDatum>>();

  if (stackingOrder === "topdown") {
    datasets = datasets.slice();
    datasets.reverse();
  }

  for (const dataset of datasets) {
    const keyToStackedDatum = new Utils.Map<string, StackedDatum>();
    const data = dataset.data();
    const dataLen = data.length;
    for (let index = 0; index < dataLen; index++) {
      const datum = data[index];
      const accessedKey = keyAccessor(datum, index, dataset);
      const key = normalizeKey(accessedKey);
      const value = +valueAccessor(datum, index, dataset);
      let offset: number;
      const offsetMap = (value >= 0) ? positiveOffsets : negativeOffsets;
      if (offsetMap.has(key)) {
        offset = offsetMap.get(key);
        offsetMap.set(key, offset + value);
      } else {
        offset = 0;
        offsetMap.set(key, value);
      }
      keyToStackedDatum.set(key, {
        offset: offset,
        value: value,
        axisValue: accessedKey,
        originalDatum: datum,
        originalDataset: dataset,
        originalIndex: index,
      });
    }
    datasetToKeyToStackedDatum.set(dataset, keyToStackedDatum);
  }
  return datasetToKeyToStackedDatum;
}

/**
 * Computes the maximum and minimum extents of each stack individually.