Model.matrix method for coxph models

Reconstruct the model matrix for a cox model.

# 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

Terry Therneau

See also

model.matrix

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)
#> [1] TRUE