nlcpy.sign

nlcpy.sign = <ufunc 'nlcpy_sign'>

Returns the element-wise indication of the sign of a number.

The sign function returns -1 if x < 0, 0 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. arary(nan+0j) is returned for complex nan inputs.

Parameters

xarray_like: Input an array or a scalar.
outndarray or 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.
wherearray_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 section Optional Keyword Arguments.

Returns

yndarray: A ndarray, containing the sign for each element in x. If x is a scalar, this function returns the result as a 0-dimension ndarray.

参考

ceil: Returns the ceiling of the input, element-wise.
floor: Returns the floor of the input, element-wise.
trunc: Returns the truncated value of the input, element-wise.

注釈

There is more than one definition of sign in common use for complex numbers. The definition used here is equivalent to $x/\sqrt{x*x}$ which is different from a common alternative, $x/|x|$ .

Examples

>>> import nlcpy as vp
>>> vp.sign([-5., 4.5])
array([-1.,  1.])
>>> vp.sign(0)
array(0)
>>> vp.sign(5-2j)
array(1.+0.j)