R Under development (unstable) (2024-02-13 r85898 ucrt) -- "Unsuffered Consequences"
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> library(survival)
> 
> #
> # The survival code was failing for certain data sets when called as
> #    survfit(Surv(time2-time1, status) ~ ......
> # The issue was how tied floating point numbers are handled, and the
> #    fact that unique(x), factor(x) and tapply(x) are not guarranteed to
> #    all be the same.  
> # This test fails in survival 2.36-5, fixed in 2.36-6.  Data sets that
> #    can cause it are few and far between.
> #
> 
> load('ties.rda')
> x <- time2 -time1
> 
> #  Here is the heart of the old problem
> #       length(unique(x))== length(table(x))
> #  And the prior fix which worked ALMOST always
> #       x <- round(x, 15)
> #       length(unique(round(x,15)))== length(table(round(x,15)))
> 
> fit1 <- survfit(Surv(x) ~1)
> length(fit1$time) == length(fit1$surv)
[1] TRUE
> 
> 
> # a second test, once "rounding.R"
> 
> tdata <- data.frame(time=c(1,2, sqrt(2)^2, 2, sqrt(2)^2),
+                     status=rep(1,5), 
+                     group=c(1,1,1,2,2))
> fit <- survfit(Surv(time, status) ~ group, data=tdata)
> 
> all.equal(sum(fit$strata), length(fit$time))
[1] TRUE
> 
> proc.time()
   user  system elapsed 
   0.79    0.12    0.90