public static async Task<Statistics<T>> Statistics<T>(this ChannelReader<T> reader,
                                                           Func<T, double> selector,
                                                           ChannelParallelOptions options)

using Amphisbaena;
using Amphisbaena.Linq;

...

int[] data = new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9};

Statistics<int> stat = await data
  .ToChannelReader()
  .Statistics();

Console.WriteLine($"range: [{stat.Min}..{stat.Max}] Sum = {stat.Sum} Average = {stat.Average}");