%% Copyright (C) 2006 Peter V. Lanspeary
%%
%% This program is free software; you can redistribute it and/or
%% modify it under the terms of the GNU General Public License
%% as published by the Free Software Foundation; either version 2,
%% or (at your option) any later version.
%%
%% This program is distributed in the hope that it will be useful,
%% but WITHOUT ANY WARRANTY; without even the implied warranty of
%% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%% GNU General Public License for more details.
%%
%% You should have received a copy of the GNU General Public License
%% along with this program; if not, write to the Free Software Foundation,
%% Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

%% Usage:
%%   [Pxx,freq] = csd(x,y,Nfft,Fs,window,overlap,range,plot_type,detrend)
%%
%%     Estimate cross power spectrum of data "x" and "y" by the Welch (1967)
%%     periodogram/FFT method.  Compatible with Matlab R11 csd and earlier.
%%     See "help pwelch" for description of arguments, hints and references
%%     --- especially hint (7) for Matlab R11 defaults.
%%
%%


function [varargout] = csd(varargin)
%%
%% Check fixed argument
  if ( nargin<2 )
    error( 'csd: Need at least 2 args. Use help csd.' );
  end
  nvarargin = length(varargin);
  %% remove any pwelch RESULT args and add 'cross'
  for iarg=1:nvarargin
    arg = varargin{iarg};
    if ( ~isempty(arg) && ischar(arg) && ( strcmp(arg,'power') || ...
           strcmp(arg,'cross') || strcmp(arg,'trans') || ...
           strcmp(arg,'coher') || strcmp(arg,'ypower') ))
      varargin{iarg} = [];
    end
  end
  varargin{nvarargin+1} = 'cross';
  %%
  saved_compatib = pwelch('R11-');
  if ( nargout==0 )
    pwelch(varargin{:});
  elseif ( nargout==1 )
    Pxx = pwelch(varargin{:});
    varargout{1} = Pxx;
  elseif ( nargout>=2 )
    [Pxx,f] = pwelch(varargin{:});
    varargout{1} = Pxx;
    varargout{2} = f;
  end
  pwelch(saved_compatib);
end
