Initial data commit

Task/Statistics-Normal-distribution/Lua/statistics-normal-distribution.lua

@@ -0,0 +1,46 @@
+function gaussian (mean, variance)
+    return  math.sqrt(-2 * variance * math.log(math.random())) *
+            math.cos(2 * math.pi * math.random()) + mean
+end
+
+function mean (t)
+    local sum = 0
+    for k, v in pairs(t) do
+        sum = sum + v
+    end
+    return sum / #t
+end
+
+function std (t)
+    local squares, avg = 0, mean(t)
+    for k, v in pairs(t) do
+        squares = squares + ((avg - v) ^ 2)
+    end
+    local variance = squares / #t
+    return math.sqrt(variance)
+end
+
+function showHistogram (t)
+    local lo = math.ceil(math.min(unpack(t)))
+    local hi = math.floor(math.max(unpack(t)))
+    local hist, barScale = {}, 200
+    for i = lo, hi do
+        hist[i] = 0
+        for k, v in pairs(t) do
+            if math.ceil(v - 0.5) == i then
+                hist[i] = hist[i] + 1
+            end
+        end
+        io.write(i .. "\t" .. string.rep('=', hist[i] / #t * barScale))
+        print(" " .. hist[i])
+    end
+end
+
+math.randomseed(os.time())
+local t, average, variance = {}, 50, 10
+for i = 1, 1000 do
+    table.insert(t, gaussian(average, variance))
+end
+print("Mean:", mean(t) .. ", expected " .. average)
+print("StdDev:", std(t) .. ", expected " .. math.sqrt(variance) .. "\n")
+showHistogram(t)