[R] Correctly Setting New Seed

Ellerbe, Caitlyn Nicole ellerbcn at musc.edu
Wed May 8 20:50:42 CEST 2013


By crash, I mean that it shuts the program and no error message is provided. However, my question is more general - how to get the two versions of code below to return the same string of random numbers. The code provided will run without incident  and is only provided to make the problem clear. The true code that causes the crash isn't necessary, only that I need to be able to split it into smaller chunks while maintaining the integrity of the random sequence even if the program closes and all information is lost. 

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Ellerbe, Caitlyn Nicole
Sent: Wednesday, May 08, 2013 2:06 PM
To: r-help at R-project.org
Subject: [R] Correctly Setting New Seed

Could someone please suggest a method to store the current random seed. I'm having trouble understanding how to correctly use set.seed and .Random.seed.

Specifically, I have the following code that crashes:



set.seed(seed)

for(i in 1:10){

  print( runif(1))

}



To get around this I need to split the number of iterations into chunks:



set.seed(seed)

for(i in 1:5){

print(runif(1))

new.seed<-.Random.seed

}



set.seed(new.seed)

for(i in 6:10){

print(runif(1))

}



When I compare the sequence of numbers from the single run to the sequence from the chunked code they don't match. Is the .Random.seed argument in the wrong position or is there another way to accomplish this?

-------------------------------------------------------
Caitlyn Ellerbe

Division of Biostatistics
Department of Public Health
Medical University of South Carolina


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