# xarray.ufuncs.log2

`xarray.ufuncs.``log2` = <xarray.ufuncs._UFuncDispatcher object>

  xarray specific variant of numpy.log2. Handles xarray.Dataset, xarray.DataArray, xarray.Variable, numpy.ndarray and dask.array.Array objects with automatic dispatching.

  Documentation from numpy:

  log2(x, /, out=None, *, where=True, casting=’same_kind’, order=’K’, dtype=None, subok=True[, signature, extobj])

  Base-2 logarithm of x.

  Parameters:

  x : array_like

  > Input values.

  out : ndarray, None, or tuple of ndarray and None, 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 : array_like, optional

  > Values of True indicate to calculate the ufunc at that position, values of False indicate to leave the value in the output alone.

  **kwargs

  > For other keyword-only arguments, see the ufunc docs.

  Returns:

  y : ndarray

  > Base-2 logarithm of x.

  See also

  `log`, `log10`, `log1p`, `emath.log2`

  Notes

  New in version 1.3.0.

  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

      >>> 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])