From pmelsted at gmail.com  Sat Apr  5 06:10:03 2008
From: pmelsted at gmail.com (pmelsted at gmail.com)
Date: Sat,  5 Apr 2008 06:10:03 +0200 (CEST)
Subject: [Rd] Random seed not reset when starting R (PR#11089)
Message-ID: <20080405041003.951012834154@mail.pubhealth.ku.dk>

Full_Name: Pall Melsted
Version: 2.3.1
OS: WinXP
Submission from: (NULL) (71.240.25.175)


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



[Rd] Random seed not reset when starting R (PR#11089)
pmelsted at gmail.com