[R] random number generator: same seed used in different sessions

[Jason Liao]

Thank you, Prof. Ripley. Yes, it turned out that different R sessions
(batch mode) loaded the same work space. Inserting
rm(list=ls(all=TRUE))
on top of the code solves the problem.


--- Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:

> On Wed, 15 Jun 2005, Jason Liao wrote:
> 
> > I did several simulation sessions and the result turned out to be a
> > surprise. After some investigation, I found that different R
> sessions
> > of the program used the same seed. Simply, in R210, if I start R
> and
> > type rnorm(1), I always get the same random number. This is
> > contradictary to what is in the R document
> >
> > Initially, there is no seed;  a new one is created from the
> >     current time when one is required.  Hence, different sessions
> will
> >     give different simulation results, by default.
> 
> That is not a contradiction!  Did you ensure that this really was 
> `initially', so there is no saved workspace, no .Rprofile etc?
> See if starting with R --vanilla makes a difference.
> 
> > I just installed the development version R220. Different sessions
> of R
> > do use different seeds as expected.
> 
> There are no R versions R210 or R220: please do read the posting
> guide
> as we ask:
> 
> > PLEASE do read the posting guide!
> http://www.R-project.org/posting-guide.html
> 
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
> 


Jason Liao, http://www.geocities.com/jg_liao
Dept. of Biostatistics, http://www2.umdnj.edu/bmtrxweb
University of Medicine and Dentistry of New Jersey
683 Hoes Lane West, Piscataway‚ NJ 08854
phone 732-235-5429, School of Public Health office
phone 732-235-9824, Cancer Institute of New Jersey office