As I understand it, how R “‘normally” does it is to use the system clock 
to set the seed once per session, unless you use set.seed() to set a new seed. 
You chose to set the seed to a different value.  But from that point on, the 
pseudo random number generation continues  in the same way it “normally” 
does.  In your code below, each of your 100 histograms will be different.  If 
you then execute the for loop again (but not the set.seed(100) statement), you 
will get a different set of histograms.  The only way you would be “confined 
to set.seed(100)” is if you keep resetting the seed to 100.

Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA 98504-5204

From: C W [mailto:tmrs...@gmail.com]
Sent: Monday, March 18, 2013 11:50 AM
To: Nordlund, Dan (DSHS/RDA)
Cc: r-help
Subject: Re: [R] How to stop set.seed() besides exiting out of R?

set.seed(100)
for (i in 1:100){
    a <- rnorm(1000, mean=0, sd=1)
    hist(a)
}

#Now say, I want to simulate without being confined to set.seed(100), I just 
want to get a simulation like how R "normally" does it.

Mike

On Mon, Mar 18, 2013 at 2:40 PM, Nordlund, Dan (DSHS/RDA) 
<nord...@dshs.wa.gov<mailto:nord...@dshs.wa.gov>> wrote:
> -----Original Message-----
> From: r-help-boun...@r-project.org<mailto:r-help-boun...@r-project.org> 
> [mailto:r-help-bounces@r-<mailto:r-help-bounces@r->
> project.org<http://project.org>] On Behalf Of C W
> Sent: Monday, March 18, 2013 11:27 AM
> To: r-help
> Subject: [R] How to stop set.seed() besides exiting out of R?
>
> Hi list,
>
> I am curious how to stop the set.seed(), I don't want the same repeated
> random number.  I know I can set it to a different seed, but I don't
> want
> to go through the trouble of setting different seed every time.
>
> Thanks,
> Mike
>
Can you show us how you are using set.seed() that results in getting the same 
sequence repeatedly?  If you are doing simulations in a loop, then set the seed 
once, outside the loop.  Otherwise, I am not sure what you are doing that 
causes problems.  A reproducible example would really help.

Dan

Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA 98504-5204

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