[R] set.seed and for loop

[R Help]

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.

Sam

On Thu, Jun 9, 2011 at 12:23 PM, 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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