function setX(this,Value)
% Set private xCoords member

%   Author: A. Stothert
%   Copyright 1986-2004 The MathWorks, Inc. 
%   $Revision: 1.1.6.2 $ $Date: 2004/12/26 21:51:30 $

if ~(size(Value,2) == 2) ||...
      ~isa(Value,'double')
   errmsg = sprintf('Invalid set value, must be nx2 of doubles.');
   error(errmsg)
   return
end
this.xCoords = Value;