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ie.setup <- function(failure.time, event, ie.time, break.ties=FALSE) {
s <- !is.na(ie.time)
if(all(s)) warning('every subject had an intervening event')
if(!any(s)) stop('no intervening events')
if(any(ie.time[s] > failure.time[s]))
stop('an ie.time was after a failure.time')
if(break.ties) {
mindif <-
min(diff(sort(unique(failure.time[!is.na(failure.time)]))))
## 8Nov01 Thanks: Josh Betcher
k <- s & (ie.time==failure.time)
if(sum(k)==0) warning('break.times=T but no ties found')
ie.time[k] <- ie.time[k] - runif(sum(k),0,mindif)
}
if(any(ie.time[s]==failure.time[s]))
stop('ie.times not allowed to equal failure.times')
n <- length(failure.time)
reps <- ifelse(is.na(ie.time), 1, 2)
subs <- rep(1:n, reps)
start <- end <- ev <- ie.status <- vector('list', n)
start[] <- 0
end[] <- failure.time
ev[] <- event
ie.status[] <- 0
for(i in seq(along=s)[s]) {
start[[i]] <- c(0, ie.time[i])
end[[i]] <- c(ie.time[i], failure.time[i])
ev[[i]] <- c(0, event[i])
ie.status[[i]] <- c(0, 1)
}
start <- unlist(start)
end <- unlist(end)
ev <- unlist(ev)
ie.status <- unlist(ie.status)
u <- units(failure.time)
units(end) <- if(u=='')'Day' else u
s <- !is.na(start+end) & (end <= start)
if(any(s)) {
cat('stop time <= start time:\n')
print(cbind(start=start[s], end=end[s]))
stop()
}
S <- Surv(start, end, ev)
list(S=S, ie.status=ie.status, subs=subs, reps=reps)
}
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