Tetracycline2 package:nlme R Documentation _P_h_a_r_m_a_c_o_k_i_n_e_t_i_c_s _o_f _t_e_t_r_a_c_y_c_l_i_n_e _D_e_s_c_r_i_p_t_i_o_n: The 'Tetracycline2' data frame has 40 rows and 4 columns. _F_o_r_m_a_t: This data frame contains the following columns: _c_o_n_c a numeric vector _T_i_m_e a numeric vector _S_u_b_j_e_c_t an ordered factor with levels '4' < '5' < '2' < '1' < '3' _F_o_r_m_u_l_a_t_i_o_n a factor with levels 'Berkmycin' 'tetramycin' _S_o_u_r_c_e: Pinheiro, J. C. and Bates, D. M. (2000), _Mixed-Effects Models in S and S-PLUS_, Springer, New York.