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Commit e003e82

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BUG: np.cov transpose control
* Fixes #27658 * Use a more sensible filter for controlling the decision to transpose the design matrix received by `np.cov`. * Add a release note.
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* `numpy.cov` now properly transposes single-row (2d array) design matrices
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when ``rowvar=False``. Previously, single-row design matrices would
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return a scalar in this scenario, which is not correct, so this
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is a behavior change and an array of the appropriate shape will
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now be returned.

‎numpy/lib/_function_base_impl.py

Copy file name to clipboardExpand all lines: numpy/lib/_function_base_impl.py
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@@ -2736,7 +2736,7 @@ def cov(m, y=None, rowvar=True, bias=False, ddof=None, fweights=None,
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dtype = np.result_type(m, y, np.float64)
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X = array(m, ndmin=2, dtype=dtype)
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if not rowvar and X.shape[0] != 1:
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if not rowvar and m.ndim != 1:
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X = X.T
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if X.shape[0] == 0:
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return np.array([]).reshape(0, 0)

‎numpy/lib/tests/test_function_base.py

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@@ -2509,6 +2509,12 @@ def test_cov_dtype(self, test_type):
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res = cov(cast_x1, dtype=test_type)
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assert test_type == res.dtype
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def test_gh_27658(self):
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x = np.ones((3, 1))
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expected = np.cov(x, ddof=0, rowvar=True)
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actual = np.cov(x.T, ddof=0, rowvar=False)
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assert_allclose(actual, expected, strict=True)
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class Test_I0:
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