R: Add strata to a Surv object

stratifySurv {glmnet} | R Documentation

## Add strata to a Surv object

### Description

Helper function to add strata as an attribute to a Surv object. The output of this function can be used as the response in `glmnet()` for fitting stratified Cox models.

### Usage

    stratifySurv(y, strata = rep(1, length(y)))

### Arguments

`y` | A Surv object.
`strata` | A vector of length equal to the number of observations in y, indicating strata membership. Default is all belong to same strata.

### Details

When fitting a stratified Cox model with `glmnet()`, strata should be added to a `Surv` response with this helper function. Note that it is not sufficient to add strata as an attribute to the `Surv` response manually: if the result does not have class `stratifySurv`, subsetting of the response will not work properly.

### Value

An object of class `stratifySurv` (in addition to all the classes `y` belonged to).

### Examples

    y <- survival::Surv(1:10, rep(0:1, length.out = 10))
    strata <- rep(1:3, length.out = 10)
    y2 <- stratifySurv(y, strata)  # returns stratifySurv object

[Package glmnet version 4.1-2 Index]