I have a 1 by N double array consisting of 1 and 0. I would like to map all the 1 to symbol '-3' and '3' and all the 0 to symbol '-1' and '1' equally. Below is my code. As my array is approx 1 by 8 million, it is taking a very long time. How to speed things up?

[row,ll] = size(Data);
sym_zero = -1;
sym_one = -3;
for loop = 1 : row
    if Data(loop,1) == 0
        Data2(loop,1) = sym_zero;
                     if sym_zero == -1
                         sym_zero = 1;
                     else
                         sym_zero = -1;
                     end
    else
        Data2(loop,1) = sym_one;
                     if sym_one == -3
                         sym_zero = 3;
                     else
                         sym_zero = -3;
                     end
    end
end