how to make low frequency and high frequency subbands in DTCWT i am having counfused in this. i am using prof ivan selesnick function of cplxdual2d

i am working on this function

x = rand(256);

J = 5;

[Faf, Fsf] = FSfarras;

[af, sf] = dualfilt1;

w = cplxdual2D(x, J, Faf, af);

y = icplxdual2D(w, J, Fsf, sf);

err = x - y;

max(max(abs(err)))

how i will add low frequency and high frequency subbands after the w = cplxdual2D(x, J, Faf, af) command kindly guide me one step that i can do further more