-
numpy.log2(x[, out]) =
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Base-2 logarithm of
x
.Parameters: x : array_like
Input values.
Returns: y : ndarray
Base-2 logarithm of
x
.Notes
New in version 1.3.0.
Logarithm is a multivalued function: for each
x
there is an infinite number ofz
such that2**z = x
. The convention is to return thez
whose imaginary part lies in[-pi, pi]
.For real-valued input data types,
log2
always returns real output. For each value that cannot be expressed as a real number or infinity, it yieldsnan
and sets theinvalid
floating point error flag.For complex-valued input,
log2
is a complex analytical function that has a branch cut[-inf, 0]
and is continuous from above on it.log2
handles the floating-point negative zero as an infinitesimal negative number, conforming to the C99 standard.Examples
>>> x = np.array([0, 1, 2, 2**4]) >>> np.log2(x) array([-Inf, 0., 1., 4.])
>>> xi = np.array([0+1.j, 1, 2+0.j, 4.j]) >>> np.log2(xi) array([ 0.+2.26618007j, 0.+0.j , 1.+0.j , 2.+2.26618007j])
numpy.log2()
2017-01-10 18:14:53
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