[R] set.seed ( ) function

Joshua Wiley jwiley.psych at gmail.com
Fri Apr 22 05:27:24 CEST 2011


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:


> 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



> 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

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