function  y = fnxt(x,t)
%
%      funxt(x,t) is an example of a relatively simple
%      function of two variables  which can be used by
%      MATLAB as required.  You can copy it to use as
%      the basis for making your own functions.  Note
%      that only the function  name  (in  this  case
%      'funxt' ) is known outside this routine.  You
%      can use anything you like  instead  of, or as
%      well as, x,t and y etc.
%
y = -x;

