simpleMovingAverage function

List<double> simpleMovingAverage(List<num> values, int size)

Simple moving average of values over window size. Audited: 2026-06-12 11:26 EDT

Implementation

List<double> simpleMovingAverage(List<num> values, int size) {
  // No window fits when size is non-positive or larger than the data, so there
  // are no averages to emit — return empty rather than a partial/garbage window.
  if (size < 1 || values.length < size) return <double>[];
  final List<double> out = <double>[];
  // Seed the running sum with the first full window.
  double sum = 0;
  for (int i = 0; i < size; i++) {
    sum += values[i].toDouble();
  }
  out.add(sum / size);
  // Slide the window by adjusting the running sum — subtract the element leaving
  // the window, add the one entering — so each step is constant-time;
  // recomputing the whole window sum at every position would instead make the
  // total cost grow with the window size.
  for (int i = size; i < values.length; i++) {
    sum = sum - values[i - size].toDouble() + values[i].toDouble();
    out.add(sum / size);
  }
  return out;
}