Given a data set in standard format (with one row per subject/observation),
this function adds a column with the specified exposure time points
and a column with respective exposures, created from rng_fun.
This function should usually only be used to create data sets passed
to sim_pexp.
add_tdc(data, tz, rng_fun, ...)A data set with variables specified in formula.
A numeric vector of exposure times (relative to the
beginning of the follow-up time t)
A random number generating function that creates
the time-dependent covariates at time points tz.
First argument of the function should be n, the number of
random numbers to generate. Within add_tdc, n will be set
to length(tz).
Currently not used.