diff options
Diffstat (limited to 'Lib')
| -rw-r--r-- | Lib/statistics.py | 6 | ||||
| -rw-r--r-- | Lib/test/test_statistics.py | 12 |
2 files changed, 16 insertions, 2 deletions
diff --git a/Lib/statistics.py b/Lib/statistics.py index c76a6ca..93a4633 100644 --- a/Lib/statistics.py +++ b/Lib/statistics.py @@ -682,8 +682,10 @@ def _ss(data, c=None): calculated from ``c`` as given. Use the second case with care, as it can lead to garbage results. """ - if c is None: - c = mean(data) + if c is not None: + T, total, count = _sum((x-c)**2 for x in data) + return (T, total) + c = mean(data) T, total, count = _sum((x-c)**2 for x in data) # The following sum should mathematically equal zero, but due to rounding # error may not. diff --git a/Lib/test/test_statistics.py b/Lib/test/test_statistics.py index 5c3b1fd..bf415dd 100644 --- a/Lib/test/test_statistics.py +++ b/Lib/test/test_statistics.py @@ -2089,6 +2089,10 @@ class TestVariance(VarianceStdevMixin, NumericTestCase, UnivariateTypeMixin): self.assertEqual(result, exact) self.assertIsInstance(result, Decimal) + def test_center_not_at_mean(self): + data = (1.0, 2.0) + self.assertEqual(self.func(data), 0.5) + self.assertEqual(self.func(data, xbar=2.0), 1.0) class TestPStdev(VarianceStdevMixin, NumericTestCase): # Tests for population standard deviation. @@ -2101,6 +2105,11 @@ class TestPStdev(VarianceStdevMixin, NumericTestCase): expected = math.sqrt(statistics.pvariance(data)) self.assertEqual(self.func(data), expected) + def test_center_not_at_mean(self): + # See issue: 40855 + data = (3, 6, 7, 10) + self.assertEqual(self.func(data), 2.5) + self.assertEqual(self.func(data, mu=0.5), 6.5) class TestStdev(VarianceStdevMixin, NumericTestCase): # Tests for sample standard deviation. @@ -2118,6 +2127,9 @@ class TestStdev(VarianceStdevMixin, NumericTestCase): expected = math.sqrt(statistics.variance(data)) self.assertEqual(self.func(data), expected) + def test_center_not_at_mean(self): + data = (1.0, 2.0) + self.assertEqual(self.func(data, xbar=2.0), 1.0) class TestGeometricMean(unittest.TestCase): |