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Module « numpy.emath »

Fonction log2 - module numpy.emath

Signature de la fonction log2

def log2(x) 

Description

help(numpy.emath.log2)

Compute the logarithm base 2 of `x`.

Return the "principal value" (for a description of this, see
`numpy.log2`) of :math:`log_2(x)`. For real `x > 0`, this is
a real number (``log2(0)`` returns ``-inf`` and ``log2(np.inf)`` returns
``inf``). Otherwise, the complex principle value is returned.

Parameters
----------
x : array_like
   The value(s) whose log base 2 is (are) required.

Returns
-------
out : ndarray or scalar
   The log base 2 of the `x` value(s). If `x` was a scalar, so is `out`,
   otherwise an array is returned.

See Also
--------
numpy.log2

Notes
-----
For a log2() that returns ``NAN`` when real `x < 0`, use `numpy.log2`
(note, however, that otherwise `numpy.log2` and this `log2` are
identical, i.e., both return ``-inf`` for `x = 0`, ``inf`` for `x = inf`,
and, notably, the complex principle value if ``x.imag != 0``).

Examples
--------

We set the printing precision so the example can be auto-tested:

>>> np.set_printoptions(precision=4)

>>> np.emath.log2(8)
3.0
>>> np.emath.log2([-4, -8, 8])
array([2.+4.5324j, 3.+4.5324j, 3.+0.j    ])

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