Add or remove a covariate term from an exposure-response TTE model

Add or remove a single covariate term from an existing ertte model, returning a new fitted model object.

Usage

ertte_add_term(mod, term, quiet = FALSE)

ertte_remove_term(mod, term, quiet = FALSE)

Arguments

mod: An ertte model object, as returned by ertte_model()
term: A one-sided formula naming the term to add/remove, e.g. ~ sex
quiet: If TRUE, suppress the warning issued when the term can't be added/removed (because it's already in the model / isn't in the model, respectively)

Value

An ertte model object. If the term can't be added/removed (see quiet), the original mod is returned unchanged.

Details

These functions are not typically called directly; they underpin ertte_scm_forward() and ertte_scm_backward(). Named and shaped to match the companion erglm package's erglm_add_term()/erglm_remove_term(): covariates enter as plain additive terms on the AFT location scale (linear for continuous covariates, factor levels for categorical ones) – the richer "continuous covariate as power function" parameterisation described in the package's design issue is not yet implemented (see AGENTS.md).

Examples

mod <- ertte_model(survival::Surv(time, event) ~ aucss, ertte_data)
mod2 <- ertte_add_term(mod, ~ sex)
mod3 <- ertte_remove_term(mod2, ~ sex)