[Rd] round, unique and factor

[Terry Therneau]

 Survfit had a bug in some prior releases due to the use of both
unique(times) and table(times); I fixed it by rounding to 15 digits per
the manual page for as.character.  Yes, I should ferret out all the
usages instead, but this was fast and it cured the user's problem.
  The bug is back!  A data set from a local colleage triggers it.  
I can send the rda file to anyone who wishes.  

 The current code has
     digits <- floor((.Machine$double.digits) * 
                    logb(.Machine$double.base,10)) #base 10 digits
     Y[,1] <- signif(Y[,1], digits)

which gives 15 digits; should I subtract one more?
  
Should the documentation change?

In the meantime I'm looking at the more permanent fix of turning time
into a factor, then back at the very end.  Because it is a bigger change
the potential for breakage is higer, however.

Terry T.

tmt45% R --vanilla

R version 2.12.2 (2011-02-25)
Copyright (C) 2011 The R Foundation for Statistical Computing
ISBN 3-900051-07-0
Platform: x86_64-unknown-linux-gnu (64-bit)

> load('test.rda')
> ls()
[1] "temp2"
> temp2 <- round(temp2, 15)
> length(unique(temp2))
[1] 954
> length(table(temp2))
[1] 942
> .Machine$double.eps
[1] 2.220446e-16
> range(temp2)
[1]  0.0000 26.0397

Terry T.