function dws = dwstats( f, d, S )
% DWSTATS - Calculate statistics from directional wave spectra
% dws = dwstats( f, d, S )
%
% Inputs:
%   f - Frequency bin centers (evenly spaced, Hz)
%   d - Directional bin centers (evenly spaced, Degrees)
%   S - Sea-surface spectra

df = f(2)-f(1)
dd = d(2)-d(1)
dws.Hrms = 2*sqrt(2)*sqrt(sum(sum(real(S)*df*dd)));