Initial data commit

Task/Statistics-Normal-distribution/Elixir/statistics-normal-distribution.elixir

@@ -0,0 +1,30 @@
+defmodule Statistics do
+  def normal_distribution(n, w\\5) do
+    {sum, sum2, hist} = generate(n, w)
+    mean = sum / n
+    stddev = :math.sqrt(sum2 / n - mean*mean)
+
+    IO.puts "size:   #{n}"
+    IO.puts "mean:   #{mean}"
+    IO.puts "stddev: #{stddev}"
+    {min, max} = Map.to_list(hist)
+                 |> Enum.filter_map(fn {_k,v} -> v >= n/120/w end, fn {k,_v} -> k end)
+                 |> Enum.min_max
+    Enum.each(min..max, fn i ->
+      bar = String.duplicate("=", trunc(120 * w * Map.get(hist, i, 0) / n))
+      :io.fwrite "~4.1f: ~s~n", [i/w, bar]
+    end)
+    IO.puts ""
+  end
+
+  defp generate(n, w) do
+    Enum.reduce(1..n, {0, 0, %{}}, fn _,{sum, sum2, hist} ->
+      z = :rand.normal
+      {sum+z, sum2+z*z, Map.update(hist, round(w*z), 1, &(&1+1))}
+    end)
+  end
+end
+
+Enum.each([100,1000,10000], fn n ->
+  Statistics.normal_distribution(n)
+end)