Epi: effx.match – R documentation

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effx.match

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)

Epi

Statistical Analysis in Epidemiology

v2.44

GPL-2

Authors

Bendix Carstensen [aut, cre], Martyn Plummer [aut], Esa Laara [ctb], Michael Hills [ctb]

Initial release

2021-02-28