@tanstack/charts/dist/transform-rolling-window.js

A chart grammar for TypeScript and JavaScript. Marks consume your data directly, channels describe visual encodings, and the engine compiles them into a renderer-neutral keyed scene. TanStack's compact scales cover common numeric and categorical mappings.

import {
  materializeGroups,
  orderedIndexes,
  toArray
} from "./transform-internal.js";
import {
  assertTransformOutputNames,
  prepareOutputs,
  reducePreparedOutputs
} from "./transform-reduce-internal.js";
function rollingWindow(source, options) {
  const data = toArray(source);
  const size = normalizeWindowSize(options.size);
  assertTransformOutputNames(
    options.outputs,
    ["source", "sourceIndexes"],
    "rollingWindow"
  );
  const preparedOutputs = prepareOutputs(data, options.outputs);
  return materializeGroups(data, options.by).flatMap(({ group, indexes }) => {
    const ordered = orderedIndexes(
      data,
      indexes,
      options.orderBy,
      options.order
    );
    return ordered.flatMap((index, position) => {
      const windowIndexes = selectedWindow(
        ordered,
        position,
        size,
        options.anchor ?? "end"
      );
      if (options.partial === false && windowIndexes.length < size) return [];
      return [
        {
          ...data[index],
          source: windowIndexes.map(
            (sourceIndex) => data[sourceIndex]
          ),
          sourceIndexes: windowIndexes,
          ...reducePreparedOutputs(
            data,
            windowIndexes,
            group,
            preparedOutputs
          )
        }
      ];
    });
  });
}
function normalizeWindowSize(value) {
  if (!Number.isFinite(value) || value <= 0) {
    throw new TypeError("rollingWindow: size must be a positive finite number");
  }
  return Math.floor(value);
}
function selectedWindow(indexes, position, size, anchor) {
  const start = anchor === "start" ? position : anchor === "middle" ? position - Math.floor((size - 1) / 2) : position - size + 1;
  const end = anchor === "end" ? position + 1 : start + size;
  return indexes.slice(Math.max(0, start), Math.min(indexes.length, end));
}
export {
  rollingWindow
};