diff options
| -rw-r--r-- | numpy/core/code_generators/ufunc_docstrings.py | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/numpy/core/code_generators/ufunc_docstrings.py b/numpy/core/code_generators/ufunc_docstrings.py index bfa3ad221..34ac59984 100644 --- a/numpy/core/code_generators/ufunc_docstrings.py +++ b/numpy/core/code_generators/ufunc_docstrings.py @@ -2799,7 +2799,13 @@ add_newdoc('numpy.core.umath', 'sign', """ Returns an element-wise indication of the sign of a number. - The `sign` function returns ``-1 if x < 0, 0 if x==0, 1 if x > 0``. + The `sign` function returns ``-1 if x < 0, 0 if x==0, 1 if x > 0``. nan + is returned for nan inputs. + + For complex inputs, the `sign` function returns + ``sign(x.real) + 0j if x.real != 0 else sign(x.imag) + 0j``. + + complex(nan, 0) is returned for complex nan inputs. Parameters ---------- @@ -2811,12 +2817,20 @@ add_newdoc('numpy.core.umath', 'sign', y : ndarray The sign of `x`. + Notes + ----- + There is more than one definition of sign in common use for complex + numbers. The definition used here is equivalent to :math:`x/\\sqrt{x*x}` + which is different from a common alternative, :math:`x/|x|`. + Examples -------- >>> np.sign([-5., 4.5]) array([-1., 1.]) >>> np.sign(0) 0 + >>> np.sign(5-2j) + (1+0j) """) |