numpy.sign#

numpy.sign(x,/,out=None,*,where=True,casting='same_kind',order='K',dtype=None,subok=True[,signature])=<ufunc'sign'>#

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

Thesign function returns-1ifx<0,0ifx==0,1ifx>0. nanis returned for nan inputs.

For complex inputs, thesign function returnsx/abs(x), thegeneralization of the above (and0ifx==0).

Changed in version 2.0.0:Definition of complex sign changed to follow the Array API standard.

Parameters:
xarray_like

Input values.

outndarray, None, or tuple of ndarray and None, optional

A location into which the result is stored. If provided, it must havea shape that the inputs broadcast to. If not provided or None,a freshly-allocated array is returned. A tuple (possible only as akeyword argument) must have length equal to the number of outputs.

wherearray_like, optional

This condition is broadcast over the input. At locations where thecondition is True, theout array will be set to the ufunc result.Elsewhere, theout array will retain its original value.Note that if an uninitializedout array is created via the defaultout=None, locations within it where the condition is False willremain uninitialized.

**kwargs

For other keyword-only arguments, see theufunc docs.

Returns:
yndarray

The sign ofx.This is a scalar ifx is a scalar.

Notes

There is more than one definition of sign in common use for complexnumbers. The definition used here,\(x/|x|\), is the more commonand useful one, but is different from the one used in numpy prior toversion 2.0,\(x/\sqrt{x*x}\), which is equivalent tosign(x.real)+0jifx.real!=0elsesign(x.imag)+0j.

Examples

>>>importnumpyasnp>>>np.sign([-5.,4.5])array([-1.,  1.])>>>np.sign(0)0>>>np.sign([3-4j,8j])array([0.6-0.8j, 0. +1.j ])
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