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Task/Statistics-Basic/Python/statistics-basic.py

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+def sd1(numbers):
+    if numbers:
+        mean = sum(numbers) / len(numbers)
+        sd = (sum((n - mean)**2 for n in numbers) / len(numbers))**0.5
+        return sd, mean
+    else:
+        return 0, 0
+
+def sd2(numbers):
+    if numbers:
+        sx = sxx = n = 0
+        for x in numbers:
+            sx += x
+            sxx += x*x
+            n += 1
+        sd = (n * sxx - sx*sx)**0.5 / n
+        return sd, sx / n
+    else:
+        return 0, 0
+
+def histogram(numbers):
+    h = [0] * 10
+    maxwidth = 50 # characters
+    for n in numbers:
+        h[int(n*10)] += 1
+    mx = max(h)
+    print()
+    for n, i in enumerate(h):
+        print('%3.1f: %s' % (n / 10, '+' * int(i / mx * maxwidth)))
+    print()
+
+if __name__ == '__main__':
+    import random
+    for i in range(1, 6):
+        n = [random.random() for j in range(10**i)]
+        print("\n##\n## %i numbers\n##" % 10**i)
+        print('  Naive  method: sd: %8.6f, mean: %8.6f' % sd1(n))
+        print('  Second method: sd: %8.6f, mean: %8.6f' % sd2(n))
+        histogram(n)