How to stop set.seed() besides exiting out of R?

I am not sure of this, but I think you can unset the seed by removing the dataset .Random.seed
from the global environment.  E.g.,

set.seed(1)
runif(5)

[1] 0.2655087 0.3721239 0.5728534 0.9082078 0.2016819

rm(list=".Random.seed", envir=globalenv())
runif(5)

[1] 0.5952379 0.3355091 0.8820192 0.7633754 0.8064312

set.seed(1)
runif(5) # same as before

[1] 0.2655087 0.3721239 0.5728534 0.9082078 0.2016819

rm(list=".Random.seed", envir=globalenv())
runif(5) # different

[1] 0.52023610 0.73407695 0.08824484 0.26977430 0.80089250

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
Of Nordlund, Dan (DSHS/RDA)
Sent: Monday, March 18, 2013 12:44 PM
To: C W
Cc: r-help
Subject: Re: [R] How to stop set.seed() besides exiting out of R?

No, you cannot unset the seed.  You can set it to a different value, but a the random
number generators always need a starting seed.  If you don?t set one, R will set one for
you , you just won?t know what it is.  And as a practical matter, given a sequence of
random numbers you can?t tell what the starting seed was.  That is the point of good
random number generators.  Each sequence of random numbers for most intents and
purposes can be considered independent from previous sets of numbers.

Hope this is helpful,

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:tmrsg11 at gmail.com]
Sent: Monday, March 18, 2013 12:19 PM
To: Nordlund, Dan (DSHS/RDA)
Cc: r-help
Subject: Re: [R] How to stop set.seed() besides exiting out of R?

Yes, I agree with you.  I guess what I was really looking for is a function like
UNset.seed()?

By having set.seed(), I can have reproducible code.  But what if I want to check my work
against what's produced from set.seed(100)?

I really want to escape from the shadow of set.seed(), can I unset it?
On Mon, Mar 18, 2013 at 3:07 PM, Nordlund, Dan (DSHS/RDA)
<NordlDJ at dshs.wa.gov<mailto:NordlDJ at dshs.wa.gov>> wrote:
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:tmrsg11 at gmail.com<mailto:tmrsg11 at 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)
<NordlDJ at dshs.wa.gov<mailto:NordlDJ at dshs.wa.gov><mailto:NordlDJ at dshs.wa.gov<
mailto:NordlDJ at dshs.wa.gov>>> wrote:

-----Original Message-----
From: r-help-bounces at r-project.org<mailto:r-help-bounces at r-project.org><mailto:r-

help-bounces at r-project.org<mailto:r-help-bounces at r-project.org>> [mailto:r-help-
bounces at r-<mailto:r-help-bounces at r-><mailto:r-help-bounces at r-<mailto:r-help-
bounces at r->>

project.org<http://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