averageBy method
Returns the average value (arithmetic mean) of all values produces by the
selector
function that is applied to each element.
Example:
[1, 2, 3].averageBy((n) => n); // 2.0
['cat', 'horse'].averageBy((s) => s.length); // 4.0
Implementation
double? averageBy(num Function(T) selector) {
if (isEmpty) {
return null;
}
return sumByDouble(selector) / length;
}