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Fonction sign - module numpy.matlib

Signature de la fonction sign

Description

sign.__doc__

sign(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True[, signature, extobj])

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``.  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
----------
x : array_like
    Input values.
out : ndarray, None, or tuple of ndarray and None, optional
    A location into which the result is stored. If provided, it must have
    a shape that the inputs broadcast to. If not provided or None,
    a freshly-allocated array is returned. A tuple (possible only as a
    keyword argument) must have length equal to the number of outputs.
where : array_like, optional
    This condition is broadcast over the input. At locations where the
    condition is True, the `out` array will be set to the ufunc result.
    Elsewhere, the `out` array will retain its original value.
    Note that if an uninitialized `out` array is created via the default
    ``out=None``, locations within it where the condition is False will
    remain uninitialized.
**kwargs
    For other keyword-only arguments, see the
    :ref:`ufunc docs <ufuncs.kwargs>`.

Returns
-------
y : ndarray
    The sign of `x`.
    This is a scalar if `x` is a scalar.

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)