for N=2:2:100

    D1=F_DM(1,N); D2=D1*D1; 

    for i=1:N-1
        for j=1:N-1
          A(i,j)=D2(i+1,j+1);
        end
    end

    aa=max(abs(eig(A)))
    cc=min(abs(eig(A)));
    bb=aa/cc;

    xx(0.5*N)=N;
    err(0.5*N)=aa/(N^2);
    frr(0.5*N)=bb/(N^2);
    grr(0.5*N)=cc;

end

    plot (xx, err, xx, frr, '--')