netsse.analys.spec.spec2d_to_spread_dist
========================================

.. py:function:: netsse.analys.spec.spec2d_to_spread_dist(S2D, theta)

   Converts the given 2-D wave spectrum into a directional spreading function
   and a 1-D wave spectrum.

   :param S2D: Directional wave spectrum, as a function of frequency and wave
               direction (with arbitrary units).
   :type S2D: array_like of shape (...,Nf,Ntheta,...)
   :param theta: Vector of wave headings (with arbitrary unit).
   :type theta: array_like of shape (Ntheta,)

   :returns: * **Sf** (*array_like of shape (...,Nf,...)*) -- One-sided variance spectrum of the waves, as a function of frequency.
             * **D** (*array_like of shape (...,Nf,Ntheta,...)*) -- Directional spreading function.

   .. seealso::

      :py:obj:`spread_dist_to_spec2d`
          Converts the given 1-D wave spectrum and directional spreading function into a 2-D wave spectrum.

   .. rubric:: Example

   >>> Sf, D = spec2d_to_spread_dist(S2D,theta)