Index: trunk/src/transform_field/diff_vel.m
===================================================================
--- trunk/src/transform_field/diff_vel.m	(revision 870)
+++ trunk/src/transform_field/diff_vel.m	(revision 870)
@@ -0,0 +1,45 @@
+%'sub_field': combines two input fields
+%
+% the two fields are subtstracted when of the same nature (scalar or
+% vector), if the coordinates do not coincide, the second field is
+% interpolated on the cooridintes of the first one
+%
+% when scalar and vectors are combined, the fields are just merged in a single matlab structure for common visualisation
+%-----------------------------------------------------------------------
+% function SubData=sub_field(Field,XmlData,Field_1)
+%
+% OUPUT: 
+% SubData: structure representing the resulting field
+%
+% INPUT: 
+% Field: matlab structure representing the first field
+% Field_1:matlab structure representing the second field
+
+%=======================================================================
+% Copyright 2008-2014, LEGI UMR 5519 / CNRS UJF G-INP, Grenoble, France
+%   http://www.legi.grenoble-inp.fr
+%   Joel.Sommeria - Joel.Sommeria (A) legi.cnrs.fr
+%
+%     This file is part of the toolbox UVMAT.
+%
+%     UVMAT 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.
+%
+%     UVMAT 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 (see LICENSE.txt) for more details.
+%=======================================================================
+
+function SubData=diff_vel(Field,XmlData,Field_1)
+
+SubData=Field;
+if exist('Field_1','var')
+          F.U=scatteredInterpolant(Field_1.X,Field_1.Y,Field_1.U,'linear');
+         SubData.U=Field.U-F.U(Field.X,Field.Y);%substract the interpolated ref to U
+          F.V=scatteredInterpolant(Field_1.X,Field_1.Y,Field_1.V,'linear');
+          SubData.V=Field.V-F.V(Field.X,Field.Y);%substract the interpolated ref to V
+end
+