infert                 package:base                 R Documentation

Infertility after Spontaneous and Induced Abortion

Description:

     This is a matched case-control study dating from before the
     availability of conditional logistic regression.

Usage:

     data(infert)

Format:


       1.  Education              0 = 0-5  years
                                  1 = 6-11 years
                                  2 = 12+  years
       2.  age                    age in years of case
       3.  parity                 count
       4.  number of prior        0 = 0
           induced abortions      1 = 1
                                  2 = 2 or more
       5.  case status            1 = case
                                  0 = control
       6.  number of prior        0 = 0
           spontaneous abortions  1 = 1
                                  2 = 2 or more
       7.  matched set number     1-83
       8.  stratum number         1-63

Note:

     One case with two prior spontaneous abortions and two prior
     induced abortions is omitted.

Source:

     Trichopoulos et al. (1976) Br. J. of Obst. and Gynaec. 83,
     645-650.

Examples:

     data(infert)
     model1 <- glm(case ~ spontaneous+induced, data=infert,family=binomial())
     summary(model1)
     ## adjusted for other potential confounders:
     summary(model2 <- glm(case ~ age+parity+education+spontaneous+induced,
                     data=infert,family=binomial()))
     ## Really should be analysed by conditional logistic regression
     ## which is equivalent to a Cox model :
     if(require(survival)){
       faketime <- rep(42,nrow(infert))
       model3 <- coxph(Surv(faketime,case)~spontaneous+induced+strata(stratum),
                     data=infert,method="exact")
       summary(model3)
       detach()# survival (conflicts)
     }

