How can i modify this code?

I would like to obtain 16 bank filters obtained in the below program using direct form 2 filters in iir. What modifcaton should i do?

Fs = 22050;                                      % Samping Frequency (Hz)
Fn = Fs/2;                                      % Nyquist Frequency
pf = linspace(20,4000,17);                      % Passband Frequencies
%pf=[20 100:100:2E+4];
cf = pf(1:end-1)+(pf(2)-pf(1))/2;               % Centre Frequencies
for k1 = 1:length(cf)
    [z(:,k1),p(:,k1),k(k1)] = butter(7, [pf(k1) pf(k1+1)]/Fn);
    [sos{k1},g{k1}] = zp2sos(z(:,k1),p(:,k1),k(k1));
    [h(:,k1),w(:,k1)] = freqz(sos{k1},512,Fs);
end
figure(1)
plot(w([1 16],:), abs(h([1 16],:)))
grid
% axis([0  0.2    ylim])
figure(2)
freqz(sos{1})
hold on
for k1 = 2:16
    freqz(sos{k1})
    %Sf(k1,:) =filtfilt(sos{k1},g{k1},S);
end
hold off

[Star Strider]

To use them in a Direct Type II configuration, you have to realize the filters as transfer functions, not second-order-section matrices. You need the numerator and denominator polynomials.

I haven’t done anything with Direct Form filters since graduate school (back in the Precambrian). I do not remember them fondly.

I’m not posting this as an Answer because it isn’t one.