how to compare all vector indexes with a constant value and switch the value of another variable (0 1) based on that

I have a 1x24 vector (a). I should define a command in Matlab which compare all 24 values of a vector (a) with a certain value (mean (b)) and if the vector (a) item is greater than certain value (mean (b)), ''I'' sets 1 and if the vector item is less than certain value ''I'' sets 0. I wrote the below code:

for i=1:length(a)
if a(i) >= mean(b)
I = 1;
else
I = 0;
end
end  

But it implements the comparison only for the last index of vector a and sets I=0. How can I fix the command that do the comparison for all indexes of vector a?