

   RRiisskk FFaaccttoorrss AAssssoocciiaatteedd wwiitthh LLooww IInnffaanntt BBiirrtthh WWeeiigghhtt

   AArrgguummeenntts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

   SSUUMMMMAARRYY::

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

   DDAATTAA DDEESSCCRRIIPPTTIIOONN::

        This data frame contains the following columns:

   SSOOUURRCCEE::

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

   EExxaammpplleess::

        attach(birthwt)
        race <- factor(race, labels=c("white", "black", "other"))
        ptd <- factor(ptl > 0)
        ftv <- merge.levels(factor(ftv), c(1,2,3,3,3,3), c("0", "1", "2+"))
        ftv <- factor(ftv)
        levels(ftv)[-(1:2)] <- "2+"
        bwt <- data.frame(low,age,lwt,race,smoke,ptd,ht,ui,ftv)
        detach("birthwt")
        options(contrasts = c("contr.treatment", "contr.poly"))
        glm(low ~ ., binomial, bwt)

