R: Model.matrix method for coxph models

model.matrix.coxph {survival}

R Documentation

Model.matrix method for coxph models

Description

Reconstruct the model matrix for a cox model.

Usage

## S3 method for class 'coxph'
model.matrix(object, data=NULL, contrast.arg =
 object$contrasts, ...)

Arguments

`object`	the result of a `coxph` model
`data`	optional, a data frame from which to obtain the data
`contrast.arg`	optional, a contrasts object describing how factors should be coded
`...`	other possible argument to `model.frame`

Details

When there is a data argument this function differs from most of the other model.matrix methods in that the response variable for the original formula is not required to be in the data.

If the data frame contains a terms attribute then it is assumed to be the result of a call to model.frame, otherwise a call to model.frame is applied with the data as an argument.

Value

The model matrix for the fit

Author(s)

Terry Therneau

Examples

fit1 <- coxph(Surv(time, status) ~ age + factor(ph.ecog), data=lung)
xfit <- model.matrix(fit1)

fit2 <- coxph(Surv(time, status) ~ age + factor(ph.ecog), data=lung,
                                 x=TRUE)
all.equal(model.matrix(fit1), fit2$x)

[Package survival version 3.8-3 Index]