function compseq = ndnacomplement(seq)
%#codegen
    assert(all(seq==1 | seq==2 | seq==3 | seq==4));
    compseq = seq;
    compseq(seq==1) = 4;
    compseq(seq==2) = 3;
    compseq(seq==3) = 2;
    compseq(seq==4) = 1;
    
end