function [var_rho]=oct_u2rho_2d(var_u)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% transfert a field at u points to a field at rho points
% 
%  Further Information:  
%  http://www.croco-ocean.org
%  
%  This file is part of CROCOTOOLS
%
%  CROCOTOOLS 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 of the License,
%  or (at your option) any later version.
%
%  CROCOTOOLS 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., 59 Temple Place, Suite 330, Boston,
%  MA  02111-1307  USA
%
%  Copyright (c) 2001-2006 by Pierrick Penven 
%  e-mail:Pierrick.Penven@ird.fr  
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

[Mp,L]=size(var_u);
Lp=L+1;
Lm=L-1;
var_rho=zeros(Mp,Lp);
var_rho(:,2:L)=0.5*(var_u(:,1:Lm)+var_u(:,2:L));
var_rho(:,1)=var_rho(:,2);
var_rho(:,Lp)=var_rho(:,L);

return

