R: Function to calculate effects for individually matched...

effx.match {Epi} | R Documentation

## Function to calculate effects for individually matched case-control studies

### Description

The function calculates the effects of an exposure on a response, possibly stratified by a stratifying variable, and/or controlled for one or more confounding variables.

### Usage

    effx.match(response,
    exposure,
    match,
    strata=NULL,
    control=NULL,
    base=1,
    digits=3,
    alpha=0.05,
    data=NULL)

### Arguments

`response` | The `response` variable - must be numeric
`exposure` | The `exposure` variable can be numeric or a factor
`match` | The variable which identifies the matched sets
`strata` | The `strata` stratifying variable - must be a factor
`control` | The `control` variable(s). These are passed as a list if there are more than one of them.
`base` | Baseline for the effects of a categorical exposure, default 1
`digits` | Number of significant digits for the effects, default 3
`alpha` | 1 - confidence level
`data` | `data` refers to the data used to evaluate the function

### Details

Effects are calculated odds ratios. The function is a wrapper for clogit, from the survival package. The k-1 effects for a categorical exposure with k levels are relative to a baseline which, by default, is the first level. The effect of a metric (quantitative) exposure is calculated per unit of exposure. The exposure variable can be numeric or a factor, but if it is an ordered factor the order will be ignored.

### Value

`comp1` | Effects of exposure
`comp2` | Tests of significance

### Author(s)

Michael Hills

### References

www.mhills.pwp.blueyonder.co.uk

### Examples

    library(Epi)
    library(survival)
    data(bdendo)

    # d is the case-control variable, set is the matching variable.
    # The variable est is a factor and refers to estrogen use (no,yes)
    # The variable hyp is a factor with 2 levels and refers to hypertension (no, yes)
    # effect of est on the odds of being a case
    effx.match(d,exposure=est,match=set,data=bdendo)
    # effect of est on the odds of being a case, stratified by hyp
    effx.match(d,exposure=est,match=set,strata=hyp,data=bdendo)
    # effect of est on the odds of being a case, controlled for hyp
    effx.match(d,exposure=est,match=set,control=hyp,data=bdendo)

[Package Epi version 2.42 Index]