Message-ID: <BANLkTinY4mch0i0PXCWdEbEDVDLm1+XucQ@mail.gmail.com>
Date: 2011-04-22T03:27:24Z
From: Joshua Wiley
Subject: set.seed ( ) function
In-Reply-To: <4DB0F374.5040109@xnet.co.nz>
Hi,
On Thu, Apr 21, 2011 at 8:18 PM, Penny Bilton <pennybilton at xnet.co.nz> wrote:
> I am using /set.seed()/ ? before the /sample/ ? function.
>
> How does the length of the argument of /set.seed()/ ? and order of the
> digits affect how the sampling is carried out?
You can use set.seed() to specify a particular seed so that while
pseudo-random numbers are sampled, you can repeat it. For example:
set.seed(10)
rnorm(10)
set.seed(10)
rnorm(10)
>
> Specifically, I have used set.seed(123456789). Will this configuration
> give me a genuinely random sampling??
You will never get truly random sampling from a computer algorithm,
but it is darn close and more than adequate in the majority of cases.
123456789 is just a length 1 vector containing the number 123456789,
not 9 separate numbers.
Google will be able to give you a lot of information on pseudo-random
number algorithms as well as the concept of "seeds". Also see
?set.seed
Cheers,
Josh
>
>
> Thank you in anticipation.
>
> Penny.
>
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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>
--
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/