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Weibull Maximum Extreme Value Distribution

doc/source/tutorial/stats/continuous_weibull_max.rst

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.. _continuous-weibull_max:

Weibull Maximum Extreme Value Distribution

Defined for :math:x<0 and :math:c>0 .

.. math:: :nowrap:

\begin{eqnarray*} f\left(x;c\right) & = & c\left(-x\right)^{c-1}\exp\left(-\left(-x\right)^{c}\right)\\ F\left(x;c\right) & = & \exp\left(-\left(-x\right)^{c}\right)\\ G\left(q;c\right) & = & -\left(-\log q\right)^{1/c}\end{eqnarray*}

The mean is the negative of the right-skewed Frechet distribution given above, and the other statistical parameters can be computed from

.. math::

 \mu_{n}^{\prime}=\left(-1\right)^{n}\Gamma\left(1+\frac{n}{c}\right).

.. math:: :nowrap:

\begin{eqnarray*}
    \mu & = & -\Gamma\left(1+\frac{1}{c}\right) \\
    \mu_{2} & = & \Gamma\left(1+\frac{2}{c}\right) -
                  \Gamma^{2}\left(1+\frac{1}{c}\right) \\
    \gamma_{1} & = & -\frac{\Gamma\left(1+\frac{3}{c}\right) -
                            3\Gamma\left(1+\frac{2}{c}\right)\Gamma\left(1+\frac{1}{c}\right) +
                            2\Gamma^{3}\left(1+\frac{1}{c}\right)}
                           {\mu_{2}^{3/2}} \\
    \gamma_{2} & = & \frac{\Gamma\left(1+\frac{4}{c}\right) -
                           4\Gamma\left(1+\frac{1}{c}\right)\Gamma\left(1+\frac{3}{c}\right) +
                           6\Gamma^{2}\left(1+\frac{1}{c}\right)\Gamma\left(1+\frac{2}{c}\right) -
                           3\Gamma^{4}\left(1+\frac{1}{c}\right)}
                          {\mu_{2}^{2}} - 3 \\
    m_{d} & = & \begin{cases}
                    -\left(\frac{c-1}{c}\right)^{\frac{1}{c}} & \text{if}\; c > 1 \\
                    0 & \text{if}\; c <= 1
                \end{cases} \\
    m_{n} & = & -\ln\left(2\right)^{\frac{1}{c}}
\end{eqnarray*}

.. math::

 h\left[X\right]=-\frac{\gamma}{c}-\log\left(c\right)+\gamma+1

where :math:\gamma is Euler's constant and equal to

.. math::

 \gamma\approx0.57721566490153286061.

Implementation: scipy.stats.weibull_max