To detect the edge of a square wave

i have written a code to generate a square wave and to detect its both edges(positive and negative) but it won't work in that manner. pls help me to detect both edges correctly. thanks in advance

t= linspace(0,1,100);
period=0.5;
I=1;
f=0;
p=0;
i_block = 0;
for k = 1:100
   t(k)   
   i_block(k) = mod(t(k)/period, 1) > 0.5;
   if i_block(k) > 0 & i_block(k) <=1 
            p=p+1            
   else
            f=f+1        
   end;
end;

plot(t, i_block,'r')

Answer 1

[Image Analyst]

Try using diff() on the signal and look for +1 or -1.