function setXUnits(this,Value)
% Set private xUnits member

%   Author: A. Stothert
%   Copyright 1986-2004 The MathWorks, Inc. 
%   $Revision: 1.1.6.1 $ $Date: 2004/12/10 19:32:24 $

if ~isa(Value,'char')
   errmsg = sprintf('Invalid set unit value, must be char.');
   error(errmsg)
   return
end
this.xUnits = Value;