

birthwt(MASS)                                R Documentation

_R_i_s_k _F_a_c_t_o_r_s _A_s_s_o_c_i_a_t_e_d _w_i_t_h _L_o_w _I_n_f_a_n_t _B_i_r_t_h _W_e_i_g_h_t

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

     The `birthwt' data frame has 189 rows and 10 columns.
     The data were collected at Baystate Medical Center,
     Springfield, Mass during 1986.

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

     low: indicator of birth weight less than 2.5kg

     age: mother's age in years

     lwt: mother's weight in pounds at last menstrual period

    race: mother's race (`1' = white, `2' = black, `3' =
          other)

   smoke: smoking status during pregnancy

     ptl: number of previous premature labours

      ht: history of hypertension

      ui: presence of uterine irritability

     ftv: number of physician visits during the first
          trimester

     bwt: birth weight in grams

_F_o_r_m_a_t_:

     This data frame contains the following columns:

_S_o_u_r_c_e_:

     Hosmer, D.W. and Lemeshow, S. (1989) Applied Logistic
     Regression.  New York: Wiley

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

     data(birthwt)
     attach(birthwt)
     race <- factor(race, labels=c("white", "black", "other"))
     ptd <- factor(ptl > 0)
     ftv <- factor(ftv)
     levels(ftv)[-(1:2)] <- "2+"
     bwt <- data.frame(low=factor(low), age, lwt, race,
         smoke=(smoke>0), ptd, ht=(ht>0), ui=(ui>0), ftv)
     detach("birthwt")
     options(contrasts = c("contr.treatment", "contr.poly"))
     glm(low ~ ., binomial, bwt)

