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

From: Prof Brian Ripley <>
Date: Thu 16 Jun 2005 - 02:31:09 EST

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!

Brian D. Ripley,        
Professor of Applied Statistics,
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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Received on Thu Jun 16 02:36:47 2005

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