[R] set.seed and for loop

[Duncan Murdoch]

On 09/06/2011 11:48 AM, jim holtman wrote:
> If you feel the need to go back and recreate a random series, then
> same the seed (.Random.seed) and restore it:

This works in this example, but wouldn't work with all RNGs, because 
some of them save state outside of .Random.seed.  See ?.Random.seed for 
details.

Duncan Murdoch
> >  set.seed(1001)
> >  total<- 0
> >  data<- vector("list", 30)
> >  seeds<- vector("list", 30)
> >  for(i in 1:30) {
> +  seeds[[i]]<- .Random.seed
> +  data[[i]]<- runif(50)
> + }
> >
> >  .Random.seed<- seeds[[23]]  # restore
> >  data.23<- runif(50)
> >  data.23
>   [1] 0.684727876 0.592993730 0.879359238 0.454304600 0.754685981
> 0.119436749 0.527867847 0.265443455
>   [9] 0.887112712 0.043309227 0.001381898 0.403483404 0.042224167
> 0.698174037 0.334604909 0.059465646
> [17] 0.374227434 0.014508142 0.265783354 0.023154917 0.668829829
> 0.184914632 0.479524914 0.644859846
> [25] 0.497644242 0.569325789 0.257636746 0.720526541 0.541526487
> 0.904469943 0.755720327 0.729912488
> [33] 0.388004197 0.940454649 0.545474130 0.285013104 0.379244716
> 0.012338111 0.192581106 0.535863633
> [41] 0.496777643 0.323488796 0.414391018 0.971135722 0.763092648
> 0.120187724 0.402572384 0.081896175
> [49] 0.303378141 0.002711767
> >  data[[23]]
>   [1] 0.684727876 0.592993730 0.879359238 0.454304600 0.754685981
> 0.119436749 0.527867847 0.265443455
>   [9] 0.887112712 0.043309227 0.001381898 0.403483404 0.042224167
> 0.698174037 0.334604909 0.059465646
> [17] 0.374227434 0.014508142 0.265783354 0.023154917 0.668829829
> 0.184914632 0.479524914 0.644859846
> [25] 0.497644242 0.569325789 0.257636746 0.720526541 0.541526487
> 0.904469943 0.755720327 0.729912488
> [33] 0.388004197 0.940454649 0.545474130 0.285013104 0.379244716
> 0.012338111 0.192581106 0.535863633
> [41] 0.496777643 0.323488796 0.414391018 0.971135722 0.763092648
> 0.120187724 0.402572384 0.081896175
> [49] 0.303378141 0.002711767
> >
>
>
> On Thu, Jun 9, 2011 at 11:23 AM, Samuel Le<Samuel.Le at 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-bounces at r-project.org [mailto:r-help-bounces at 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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