Upper half of generalized normal distribution

The probability density function for the upper half of a generalized normal distribution is:

.. math::

f(x, k) = \frac{k}{\Gamma(1/k)} \exp(-|x|^k)

where :math:x > 0, k > 0. The following plots show the pdf and cdf:

.. image:: ../../../../tests/imgs/stats/continuous/halfgennorm/halfgennormpdf.png :align: center :width: 480

.. image:: ../../../../tests/imgs/stats/continuous/halfgennorm/halfgennormcdf.png :align: center :width: 480