ipcw.aftreg: Inverse probability censoring weights (IPCW) for...
In adibender/ldatools: Utility functions for life-time data analysis

This function uses eha::aftreg to estimate IPCW for left-truncated data based on an AFT Weibull model. Initially designed to be used in conjunction with pec::pec, however, pec does not support eha::aftreg as a method for calculation of IPCWs. The function is loosely based on pec:::ipcw.cox and only supports calculating IPCWs at specified times (what = "IPCW.times"; see what argument in ?pec::ipcw).

## S3 method for class 'aftreg'
ipcw(
  formula,
  data,
  method = "aftreg",
  args,
  times,
  subjectTimes,
  subjectTimesLag,
  what = "IPCW.times"
)

`formula`	A survival formula like, `Surv(time,status)~1`, where as usual status=0 means censored. The status variable is internally reversed for estimation of censoring rather than survival probabilities. Some of the available models (see argument `model`) will use predictors on the right hand side of the formula.
`data`	The data used for fitting the censoring model
`method`	Censoring model used for estimation of the (conditional) censoring distribution.
`args`	A list of arguments which is passed to method
`times`	For `what="IPCW.times"` a vector of times at which to compute the probabilities of not being censored.
`subjectTimes`	For `what="IPCW.subjectTimes"` a vector of individual times at which the probabilities of not being censored are computed.
`subjectTimesLag`	If equal to `1` then obtain `G(T_i-\|X_i)`, if equal to `0` estimate the conditional censoring distribution at the subjectTimes, i.e. (`G(T_i\|X_i)`).
`what`	Decide about what to do: If equal to `"IPCW.times"` then weights are estimated at given `times`. If equal to `"IPCW.subjectTimes"` then weights are estimated at individual `subjectTimes`. If missing then produce both.