There is a difference between R and S (or S-Plus, I'm not sure about
that) concerning the generation of random numbers.
If an error occurs during the execution of a function, the seed is
restored to its old value in S-Plus, but not in R. This feature of S-Plus
has just turned out to be very useful for me because I got an error
message during a small simulation for a certain choice of parameters.
Here is a silly example:
R> silly<-function()
+ {
+ tmp<-rnorm(5)
+ unknownfunction()
+ }
R> .Random.seed
[1] 8886 1153 10190
R> silly()
Error: couldn't find function "unknownfunction"
R> .Random.seed
[1] 9859 1963 19516
Splus> silly<-function()
+ {
+ tmp<-rnorm(5)
+ unknownfunction()
+ }
Splus> .Random.seed
[1] 37 31 60 6 22 0 47 15 0 30 41 0
Splus> silly()
Error in silly(): couldn't find function "unknownfunction"
Dumped
Splus> .Random.seed
[1] 37 31 60 6 22 0 47 15 0 30 41 0
Arne Kovac
--
Arne Kovac
School of Mathematics Phone: +44 (0117) 942 7551
University of Bristol A.Kovac@bristol.ac.uk
University Walk http://www.stats.bris.ac.uk/~maak
Bristol, BS8 1TW, U.K.
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