infert {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)){
  oT <- T; oF <- F; T <- TRUE; F <- FALSE # survival fails otherwise
  faketime <- rep(42,nrow(infert))
  model3 <- coxph(Surv(faketime,case)~spontaneous+induced+strata(stratum),
                data=infert,method="exact")
  summary(model3)
  detach()# survival (conflicts)
  T <- oT; F <- oF
}

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