nums.numpy.log2

nums.numpy.log2(x, out=None, where=True, **kwargs)[source]

Base-2 logarithm of x.

This docstring was copied from numpy.log2.

Some inconsistencies with the NumS version may exist.

Parameters

  • x (BlockArray) – Input values.

  • out (BlockArray, None, or 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 (BlockArray, 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 ufunc docs.

Returns

y – Base-2 logarithm of x.

Return type

BlockArray

See also

log, log10, log1p

Notes

Logarithm is a multivalued function: for each x there is an infinite number of z such that 2**z = x. The convention is to return the z 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 yields nan and sets the invalid 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

The doctests shown below are copied from NumPy. They won’t show the correct result until you operate get().

>>> x = nps.array([0, 1, 2, 2**4])  
>>> nps.log2(x).get()  
array([-Inf,   0.,   1.,   4.])

>>> xi = nps.array([0+1.j, 1, 2+0.j, 4.j])  
>>> nps.log2(xi).get()  
array([ 0.+2.26618007j,  0.+0.j        ,  1.+0.j        ,  2.+2.26618007j])