R Under development (unstable) (2025-12-21 r89216 ucrt) -- "Unsuffered Consequences"
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> # Better control of repeats
> library(survival)
> aeq <- function(x, y, ...) all.equal(as.vector(x), as.vector(y), ...)
> 
> # When there are multiple censored rows, don't add more than we need
> baseline <- data.frame(idd=1:5,  sex=c('f', 'm')[c(1,2,1,2,2)], 
+                        futime=c(20, 30, 40, 30, 20),
+                        status= c(0, 1, 0, 1, 0))
> d2 <- data.frame(idd= rep(2:5, each=3), 
+                  day=c(0,15, 21, 0,25, 31, 0,20, 25, 0,10, 12),
+                  cmc=c(2,3,3, 3,3,4, 2,3,3, 3,4,2))
> 
> test1 <- tmerge(baseline[,1:2], baseline, id=idd, death=event(futime, status))
> test2 <- tmerge(test1, d2, id=idd, cmc= tdc(day, cmc))
> 
> # idd 2 has an obs at (0, 30), add new one at 21
> # idd 3
> aeq(test2$idd, c(1,2,2,3,3,4,4,5,5,5))
[1] "Numeric: lengths (13, 10) differ"
> aeq(test2$cmc, c(NA, 2,3,3,4,2,3,3,4,2)) 
[1] "Numeric: lengths (13, 10) differ"
> 
> proc.time()
   user  system elapsed 
   1.01    0.04    1.04