# numpy.lib.scimath.log2¶

`lib.scimath.``log2`(x)[source]

Compute the logarithm base 2 of x.

Return the “principal value” (for a description of this, see `numpy.log2`) of . 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    ])
```