netsse.analys.buoy.Fourier2spread_dist_params
=============================================

.. py:function:: netsse.analys.buoy.Fourier2spread_dist_params(a1, b1, a2, b2)

   Infers the parameters of the directional spreading distribution function
   from the Fourier coefficients, as per Kuik et al. (1988).

   :param a1: First four Fourier coefficients of the directional wave spectrum.
   :type a1: array_like of shape (Nf,)
   :param b1: First four Fourier coefficients of the directional wave spectrum.
   :type b1: array_like of shape (Nf,)
   :param a2: First four Fourier coefficients of the directional wave spectrum.
   :type a2: array_like of shape (Nf,)
   :param b2: First four Fourier coefficients of the directional wave spectrum.
   :type b2: array_like of shape (Nf,)

   :returns: * **alpha** (*array_like of shape (Nf,)*) -- Wave direction [rad].
             * **sigma** (*array_like of shape (Nf,)*) -- Directional spread [rad].
             * **gamma** (*array_like of shape (Nf,)*) -- Skewness of the directional distribution [-].
             * **delta** (*array_like of shape (Nf,)*) -- Kurtosis of the directional distribution [-].

   .. seealso::

      :py:obj:`spread_dist_params2Fourier`
          Infers the Fourier coefficients from the parameters of the directional spreading distribution function.

   .. rubric:: References

   Kuik, A. J., van Vledder, G. P., & Holthuijsen, L. H. (1988). *A Method for
   the Routine Analysis of Pitch-and-Roll Buoy Wave Data*. Journal of Physical
   Oceanography, 18(7), 1020–1034.

   .. rubric:: Example

   >>> [alpha, sigma, gamma, delta] = Fourier2spread_dist_params(a1,b1,a2,b2)