# numpy.emath.log2#

emath.log2(x)[source]#

Compute the logarithm base 2 of x.

Return the “principal value” (for a description of this, see numpy.log2) of $$log_2(x)$$. 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:
xarray_like

The value(s) whose log base 2 is (are) required.

Returns:
outndarray or scalar

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

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    ])