[Rd] Random seed not reset when starting R (PR#11089)

pmelsted at gmail.com pmelsted at gmail.com
Sat Apr 5 06:10:03 CEST 2008

Full_Name: Pall Melsted
Version: 2.3.1
Submission from: (NULL) (

Random set is not reset when starting R again. When R starts with a

[Previously saved workspace restored]

it seems that the .Random.seed variable is already set. If you quit R (and don't
save your workspace) the next time you start R .Random.seed will be set to the
same value again.

Steps to reproduce:
1. Start R afresh and type runif(1)
2. Quit R and do not save workspace
3. Start R again (make sure a previous workspace was restored) type runif(1)
again, this will be the same "random" number as before.

>From documentation on .Random.seed

     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.

This behavior is very counterintuitive and can mess up simulation results,
especially when sampling. The seed really should be set when R starts,
regardless of whether .Random.seed is set.

This bug has also been reproduced on MacOSX 10.4, R version 2.2.1

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