

strata(survival5)                            R Documentation

_I_d_e_n_t_i_f_y _S_t_r_a_t_a _V_a_r_i_a_b_l_e_s

_D_e_s_c_r_i_p_t_i_o_n_:

     This is a special function used in the context of the
     Cox survival model.  It identifies stratification vari-
     ables when they appear on the right hand side of a for-
     mula.

_U_s_a_g_e_:

     strata(..., na.group=F)

_A_r_g_u_m_e_n_t_s_:

     ...: any number of variables.  All must be the same
          length.

na.group: a logical variable, if `TRUE', then missing values
          are treated as a distinct level of each variable.

_D_e_t_a_i_l_s_:

     The result is identical to the `interaction' function,
     but for the labeling of the factors (`strata' is more
     verbose).

_V_a_l_u_e_:

     a new factor, whose levels are all possible combina-
     tions of the factors supplied as arguments.

_E_x_a_m_p_l_e_s_:

     data(ovarian)
     coxph(Surv(futime, fustat) ~ age + strata(rx), data=ovarian)

