Create an index based Schmitt Trigger

Hello, I have a function that mimics a Schmitt Trigger to translate an analog sine wave into a digital square wave. So far, I have accomplished this with a for loop and the function works as planned. However, since I have a significant amount of data to process, I would like to do this index based for speed. I cannot think of a way to make this index based so the function performes faster.

My function is below, any suggestions on how to make this index based? Is it possible?

Thanks.

function [y] = Schmitt_Trigger(x,tL,tH)
    %x is the input array that contains the analog sine wave to process. 
    %tL is the lower bound of the hysteresis and tH is the upper bound. 

    N = length(x);
    
    y = zeros(1,N);
    for i = 2:N
        y(i) = y(i-1);
        if y(i-1) == 0 && x(i)>tH 
            y(i) = 1;
        end
        if y(i-1) == 1 && x(i)<tL
            y(i) = 0;
        end
    end
end