how to impement hanning window for following code

As=40;

passbandfreq=0.01;

transitionwidth=500;

normalizedtransitionwidth=transitionwidth/fsamp

fsamp=10000;

fc=1200;

fcn=fc/fsamp

passbandfreq=10^(passbandfreq/20)-1

stopbandfreq=10^(-As/20)

delta=min(passbandfreq,stopbandfreq)

%%using hanning window

N=3.1/normalizedtransitionwidth

hn=hanning(N); % hanning

[H,f]=freqz(hn,1.512,fsamp);

mag=20*log10(abs(H))

plot(fcn,mag),grid on