On 09.06.2011 18:09, R Help wrote:
That wouldn't work because the seed is for the first iteration.

Random numbers are generated by a seed, after which the seed changes
(I don't know the mechanism for changing the seed in R, but it's
static)

That means that, if you set the seed to 1001, and then run runif
function 50 times, you'll get 50 different sets of random numbers.  If
you reset the seed to 1001 and then run runif again, the result will
be the same as data[[1]], not [[23]].  And you can't just set the seed
to 1023 because that's not how the seed changes.

I think Jim's suggestion was the best.  I was thinking of that but I
couldn't remember how to extract the seed.


Well set.seed() actually generates a seed. See ?set.seed that points us to .Random.seed (and relevant references!) which contains the actual current seed.

Uwe Ligges



Sam

On Thu, Jun 9, 2011 at 12:23 PM, Samuel Le<samuel...@srlglobal.com>  wrote:
What about:
set.seed(1001)
total<- 0
data<- vector("list", 30)
for(i in 1:30) {
  data[[i]]<- runif(50)
}
set.seed(1001)
data[[23]]<- runif(50)

HTH
Samuel

-----Original Message-----
From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On 
Behalf Of Soyeon Kim
Sent: 09 June 2011 16:15
To: r-help
Subject: [R] set.seed and for loop

Dear All,

This is hard to describe so I made a simple example.
set.seed(1001)
total<- 0
data<- vector("list", 30)
for(i in 1:30) {
  data[[i]]<- runif(50)
}
Let's call a data set runif(50).
While the for loop is running, 100 data sets  are generated.
I want to restore 23th data set (the data set generated in 23th for
loop) without the loop.
I've tried set.seed(1023) runif(50)
but this is different data from the data set gotten from 23th for loop.
How can I get 23th data set without the loop?

Thank you,
Soyeon

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