def average(arr)
arr.sum(0.0) / arr.size
end
arr = [3.14, 8.0, 2.87, 5.982, 10.0]
arr.size.downto(0) do |i|
arr_len = arr[0, i]
puts "array size #{arr_len.size} : average = #{average(arr_len)}"
end
#
# run:
#
# array size 5 : average = 5.9984
# array size 4 : average = 4.998
# array size 3 : average = 4.67
# array size 2 : average = 5.57
# array size 1 : average = 3.14
# array size 0 : average = NaN
#