Simulate censored time-to-event data from a fitted flexsurvreg model

Usage

# S3 method for flexsurvreg
simulate(
  object,
  nsim = 1,
  seed = NULL,
  newdata = NULL,
  start = NULL,
  censtime = NULL,
  tidy = FALSE,
  ...
)

Arguments

object

Object returned by flexsurvreg.

nsim

Number of simulations per row in newdata.

seed

Random number seed. This is returned with the result of this function, as described in simulate for the lm method.

newdata

Data frame defining alternative sets of covariate values to simulate with. If omitted, this defaults to the data originally used to fit the model.

start

Optional left-truncation time or times. The returned survival, hazard or cumulative hazard will be conditioned on survival up to this time. Predicted times returned with "rmst", "mean", "median" or "quantile" will be times since time zero, not times since the start time.

A vector of the same length as t can be supplied to allow different truncation times for each prediction time, though this doesn't make sense in the usual case where this function is used to calculate a predicted trajectory for a single individual. This is why the default start time was changed for version 0.4 of flexsurv - this was previously a vector of the start times observed in the data.

censtime

A right-censoring time, or vector of times matching the rows of newdata. If NULL (the default) then uncensored times to events are simulated.

tidy

If TRUE then a "tidy" or "long"-format data frame is returned, with rows defined by combinations of covariates and simulation replicates. The simulation replicate is indicated in the column named i.

If FALSE, then a data frame is returned with one row per set of covariate values, and different columns for different simulation replicates. This is the traditional format for `simulate` methods in base R.

In either case, the simulated time and indicator for whether the time is an event time (rather than a time of right-censoring) are returned in different columns.

...

Other arguments (not currently used).

Value

A data frame, with format determined by whether tidy was specified.

Examples

fit <- flexsurvreg(formula = Surv(futime, fustat) ~ rx, data = ovarian, dist="weibull")
fit2 <- flexsurvspline(formula = Surv(futime, fustat) ~ rx, data = ovarian, k=3)
nd = data.frame(rx=1:2)
simulate(fit, seed=1002, newdata=nd)
#>      time_1 event_1
#> 1  575.5959       1
#> 2 2391.6927       1
simulate(fit, seed=1002, newdata=nd, start=500)
#>      time_1 event_1
#> 1  993.9562       1
#> 2 2750.1742       1
simulate(fit2, nsim=3, seed=1002, newdata=nd)
#>     time_1   time_2    time_3 event_1 event_2 event_3
#> 1 457.8966 3564.307  943.0164       1       1       1
#> 2 419.5862  731.334 9729.0033       1       1       1
simulate(fit2, nsim=3, seed=1002, newdata=nd, start=c(500,1000))
#>     time_1    time_2    time_3 event_1 event_2 event_3
#> 1 2081.447 12780.637  4008.034       1       1       1
#> 2 2872.484  3469.562 24816.827       1       1       1