R help - May 2007 - how to reproduce the same sampled units?

Hi all,
 
Is it possible to generate the same sample number of times in R? In
SAS, using the option "seed" it is possible to reproduce exactly the
same sample. Is there any such feature in R which I can use? 
 
For further clarity,
 
for (i in 1:2)
{
samp = sample(1:1000,100,replace = FALSE)
print(samp)
}
 
For the above simulation, is it possible to generate the same sampled
units twice?
 
Any suggestion would be gratefully acknowledged.
Thanks,
Santanu
 
Santanu Pramanik
JPSM,1218J Lefrak Hall
University of Maryland,College Park
Phone no.-301-314-9916
 
 

	[[alternative HTML version deleted]]

On 02-May-07 23:25:18, Santanu Pramanik wrote:
> Hi all,
>  
> Is it possible to generate the same sample number of times in R?
> In SAS, using the option "seed" it is possible to reproduce
exactly
> the same sample. Is there any such feature in R which I can use? 
>  
> For further clarity,
>  
> for (i in 1:2)
> {
> samp = sample(1:1000,100,replace = FALSE)
> print(samp)
> }
> > For the above simulation, is it possible to generate the same sampled
> units twice?
>  
> Any suggestion would be gratefully acknowledged.
> Thanks,
> Santanu
Have a look at set.seed():

  ?set.seed

You will of course have to invoke it before you do your first run.
You cannot find out what the seed was afterwards!

For example (your example somewhat reduced):

  for (i in 1:2)
  {
  samp = sample(1:1000,10,replace = FALSE)
  print(samp)
  }
# [1] 984 587  26 920 304 247 434 392 650 279
# [1] 178 619 458 208 389 629 988 263 598 308

  for (i in 1:2)
  {
  set.seed(512534)
  samp = sample(1:1000,10,replace = FALSE)
  print(samp)
  }
# [1] 271 106 570 621 257 663 399 454 983 805
# [1] 271 106 570 621 257 663 399 454 983 805

Best wishes,
Ted.

--------------------------------------------------------------------
E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 03-May-07                                       Time: 00:56:43
------------------------------ XFMail ------------------------------

?set.seed

On Wed, 02 May 2007 18:25:18 -0500, Santanu Pramanik  
<spramanik at survey.umd.edu> wrote:
> Hi all,
> Is it possible to generate the same sample number of times in R? In
> SAS, using the option "seed" it is possible to reproduce exactly
the
> same sample. Is there any such feature in R which I can use?
> For further clarity,
> for (i in 1:2)
> {
> samp = sample(1:1000,100,replace = FALSE)
> print(samp)
> }
> For the above simulation, is it possible to generate the same sampled
> units twice?
> Any suggestion would be gratefully acknowledged.
> Thanks,
> Santanu
> Santanu Pramanik
> JPSM,1218J Lefrak Hall
> University of Maryland,College Park
> Phone no.-301-314-9916
>
> 	[[alternative HTML version deleted]]
>
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-- 
Kenneth Roy Cabrera Torres
Cel 315 504 9339