From Thomas Lumley <thomas@biostat.washington.edu>  Mon Sep 15 17:27:54 1997
From: Thomas Lumley <thomas@biostat.washington.edu> (Thomas Lumley)
Date: Mon, 15 Sep 1997 09:27:54 -0700 (PDT)
Subject: R-alpha: compatibility
In-Reply-To: <97Sep15.105405edt.26503@mailgate.bank-banque-canada.ca>
Message-ID: <Pine.SUN.3.95.970915091422.1882B-100000@troi>

On Mon, 15 Sep 1997, Paul Gilbert wrote:

> Please don't mess with the random number generator without good reason!
> You will mess me up a whole lot! You can of course change the default
> behavior of set.seed without affecting me. Here are my thoughts on
> set.seed.

I am aware of the problems with messing with random number generators,
which is why I wasn't proposing to.  In the generator we use (unlike in
S-PLUS), any seed value gives (a different part of) the same sequence of
random numbers, so seed setting is a harmless procedure.

>> Despite the fact that the Blue Book says set.seed takes an integer
> argument, and despite the fact that the Splus version of set.seed does
> take an integer argument, I don't think anyone who actually does a lot
> of random experiments would actual want to use set.seed like that.

I don't think the issue is whether set.seed() does something useful in S. 
It does *something* in S, and people use it in writing programs. They may
well want to run these programs in R (or we may want them to, especially
if they are sharing CPU time with us). The last thing we want to do is to
have a function set.seed() in R that does something qualitatively
different from the S function. 


Thomas Lumley
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R-alpha: compatibility
Thomas Lumley