


The Poisson Distribution
========================

.. function:: gsl_ran_poisson(mu)

 This function returns a random variate from the :index:`Poisson
 distribution` with mean ``mu``. The probability distribution
 for Poisson variates is,

 .. math::
   p(k) = {\mu^k \over k!} \exp(-\mu)

 for :math:`k \geq 0`.

.. function:: gsl_ran_poisson_pdf(k, mu)

 This function computes the probability :math:`p(k)` of obtaining :math:`k` from a
 Poisson distribution with mean ``mu``, using the formula given above.

.. function:: gsl_cdf_poisson_P(k, mu)

.. function:: gsl_cdf_poisson_Q(k, mu)

 These functions compute the cumulative distribution functions
 :math:`P(k), Q(k)` for the Poisson distribution with parameter ``mu``.
