Prediction function for an exposure-response TTE model

Usage

ertte_fun(object)

Arguments

object: An ertte model, as returned by ertte_model()

Value

A function with arguments param, data, and time.

The param argument should be a vector of location coefficients; defaults to coef(object) (the fitted coefficients) if not supplied.
The data argument should be a data frame or tibble; defaults to object$data (the data the model was fitted to) if not supplied.
The time argument gives the time(s) at which to evaluate the survival function; recycled against data.

Details

Takes a fitted ertte model as input and returns a function that evaluates the survival function S(t) at user-specified parameters, data, and times (e.g. for VPCs or other counterfactual simulation scenarios). Named ertte_fun() for consistency with the companion erglm/emaxnls packages' erglm_fun()/emax_fun(), which serve the same purpose for their respective model classes. The returned function checks that param is numeric and has one entry per column of the model matrix implied by data, erroring informatively rather than failing with a cryptic "non-conformable arguments" error from matrix multiplication. scale is always taken from the fitted object, not from param (the coefficient vector from coef() never includes it).

Examples

mod <- ertte_model(survival::Surv(time, event) ~ aucss, ertte_data)
mod_fun <- ertte_fun(mod)

# no arguments: reproduces the fitted model's own survival predictions
s1 <- mod_fun(time = 60)

# user modifies the parameters
par2 <- coef(mod)
par2["(Intercept)"] <- par2["(Intercept)"] + 1
s2 <- mod_fun(param = par2, time = 60)