netsse.analys.buoy.cross_spec2Fourier_coef
==========================================

.. py:function:: netsse.analys.buoy.cross_spec2Fourier_coef(Gf)

   Computes the Fourier coefficients from the cross-spectra of a
   heave-East-North wave buoy, as per Benoit et al. (1997).

   :param Gf: Cross-spectra (Heave-East-North), as a function of frequency in Hertz.
   :type Gf: array_like of shape (3,3,Nf)

   :returns: * **Sf** (*array_like of shape (Nf,)*) -- One-sided variance spectrum of the waves [m^2.s], as a function of
               frequency in Hertz.
             * **a1, a2, b1, b2** (*array_like of shape (Nf,)*) -- Frequency-dependent Fourier coefficients of the directional wave
               spectrum.

   .. seealso::

      :py:obj:`Shannon_MEMII_Newton`
          Reconstructs the directional spreading function based on the first four Fourier coefficients of a directional wave spectrum.

   .. rubric:: References

   Benoit, M., Frigaard, P., & Schäffer, H. A. (1997). *Analysing Multidirectional
   Wave Spectra: A tentative classification of available methods*. Proceedings of
   the 27th IAHR Congress, San Francisco, CA, USA (pp. 131–158). Canadian
   Government Publishing.

   .. rubric:: Example

   >>> Sf, a1, a2, b1, b2 = cross_spec2Fourier_coef(Gf)