function [z,ee,xx]=maxrel(x,y)
 e=double(x)-double(y);
 re=abs( e(x~=0)./double(x(x~=0)) );
 z=max(re);
 e2=e(x~=0);
 x2=x(x~=0);
 ee=abs(e2(re==z));
 xx=abs(double(x2(re==z)));
 if max(ee)==min(ee) & max(xx)==min(xx)
  ee=ee(1);
  xx=xx(1);
 else
  ee=[];
  xx=[];
 end