From therneau at mayo.edu  Fri Mar 15 18:47:01 2013
From: therneau at mayo.edu (Terry Therneau)
Date: Fri, 15 Mar 2013 12:47:01 -0500
Subject: [Rd] numerics from a factor
Message-ID: <51435E95.304@mayo.edu>

A problem has been pointed out by a French user of the survival package and I'm looking 
for a pointer.

 > options(OutDec= ",")
 > fit <- survfit(Surv(1:6 /2) ~ 1)
 > fit$time
[1] NA  1 NA  2 NA  3

A year or two ago some test cases that broke survfit were presented to me. The heart of 
the problem was numbers that were almost identical, where table(x) and unique(x) gave 
different counts of distinct values.
The solution was to use "ftime <- factor(time)" at the top of the code, and do all the 
calulations using the integer levels of the factor as the unique time points.  At the very 
end the numeric component "time" of the result is created using 
as.numeric(levels(ftime)).  It's this last line that breaks.

I could set the OutDec option within survfit and reset when I leave using on.exit.  Any 
other simple solutions?  Any other ways I could get caught by this issue?

Terry Therneau



[Rd] numerics from a factor
Terry Therneau