averageBy method

double averageBy(num selector(T))

Returns an average value produced by selector function applied to each element in the collection.

Implementation

double averageBy(num Function(T) selector) {
  num sum = 0.0;
  var count = 0;
  for (final element in iter) {
    final value = selector(element);
    // nan values are ignored
    if (!value.isNaN) {
      sum += value;
      count++;
    }
  }
  if (count == 0) {
    return double.nan;
  }
  return sum / count;
}