function   zerotree = checkancestors1(j,R,zerotree)



% zerotree=1 means coefficient is descended from zerotree root

% initial set zerotree=0



global N;



i = floor((j+3)/4 ); 





while i>1,

    

     

      if R(N(i,1),N(i,2))==1; 

          

          zerotree=1;

          

          break;

       

      end;

      

      i = floor((i+3)/4 );

 end