function [An, Bn, Cn, Dn, N] = qq2standard(A, B, C, D, forme)
    n = size(A)
    coeff = poly(A);
    if isequal(forme, 'diag')

    elseif isequal(forme, 'commandable')
        x = zeros(1,n);
        for k = 1:n
            x(k) = A^(k-1)*B;
        end

        y = fliplr(eye(n));
        for k = n-1:1
            y = y + fliplr(ones(1, k) * coeff(k) ,n-k); %% Les coefficients coeff(k) sont les facteurs du polynome caractéristique
        end

        N = x * y;
        [An, Bn, Cn, Dn] = changebase(A, B, C, D, N);

    elseif isequal(forme, 'observable')
            X = zeros(1,n);
            for k = 1: n
                X(k) = (eye*(A')^(k-1)+ coeff(k-1)*(A')^(k-2)+coeff(1)*eye)*(C');
            end
            M = Inv(X);
            N = M';


    end

end