Simple if else for buffer speech

Hi, how can I display the required answer 'yes' or 'no' for each ZCR calculated on each buffer frame speech?

here is the coding. It only display 1 answer. I suppose to get 23 answers. Please help me.thanks a lot.

X=wavread('speech01_denoised.wav');
N=400;
Y = buffer(X,N);
s=sum(abs(diff(Y>0)))/length(Y);%ZCR
if s<=0
    display('yes')
elseif (s>=0)
    display('no')
end