The algorithm you want is not perfectly clear, and I can't see quite how you get the output from your input. But it seems that you want something like this?
y = [-5 -4 -3 -2 -1 0 1 2 3 4 5;
-6 -5 -4 -3 -2 -1 0 1 2 3 4;
0 1 2 3 4 5 6 7 8 9 10];
nyrows = size(y,1);
output = zeros(1,nyrows);
for ny = 1:nyrows
output(ny) = find(y(ny,:)>3.5,1) - 1; % Not sure exactly which element you want
end
disp(output)
