function f = non_domination_sort_mod(x)
    M = 4;
    [N temp]= size(x);
    rank = 1;
    F(rank).f = [];
    individual = [];
    for i = 1 : N
        individual(i).n = 0;
        individual(i).p = [];
        for j = 1 : N
            dom_less = 0;
            dom_equal = 0;
            dom_more = 0;
            for k = 1 : M
                if (x(i, k) < x(j, k))
                    dom_less = dom_less + 1;
                elseif(x(i, k) ==x(j, k))
                    dom_equal = dom_equal + 1;
                else
                    dom_more = dom_more + 1;
                end
            end
            if (dom_less == 0) & (dom_equal ~= M)
                individual(i).n = individual(i).n + 1;
            elseif (dom_more == 0) & (dom_equal ~= M)
                individual(i).p = [individual(i).p j];
            end
        end
        if (individual(i).n == 0)
            x(i,M + 7) = 1;
            F(rank).f = [F(rank).f i];
        else
            x(i,M + 7) = 2;
        end
    end
    y = [];
    for j = 1 : length(F(1).f)
        y(j,:) = x(F(1).f(j),:);
    end
    f = y;