[R] set.seed ( ) function

[Joshua Wiley]

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.
>
>
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>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
http://www.joshuawiley.com/