[R] bootstrap sample for clustered data

[Liu, Lei]

Sorry for the confusion. I just want to recode the id variable to 1 to 5 in the bootstrapped sample. This way I can do e.g., a mixed effects model using the new id as the cluster. Thanks!

Lei

From: Bert Gunter [mailto:bgunter.4567 using gmail.com]
Sent: Sunday, September 16, 2018 2:21 PM
To: Liu, Lei <lei.liu using wustl.edu>
Cc: R-help <r-help using r-project.org>
Subject: Re: [R] bootstrap sample for clustered data

I can't make any sense of your post. Id 3 occurs 6 times, and 2 and 5 occur twice each in your example.. How do you get (1,1,2,2,3,3,4,4,5,5) out of that? In other words, specify the mapping of old id's to new.

Bert

Bert Gunter

"The trouble with having an open mind is that people keep coming along and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Sun, Sep 16, 2018 at 11:51 AM Liu, Lei <lei.liu using wustl.edu<mailto:lei.liu using wustl.edu>> wrote:
Hi there,

I tried to generate bootstrap samples for clustered data. Here is some code I found in the web to do the work:

id=c(1, 1, 2, 2, 3, 3, 4, 4, 5, 5)
y=c(.5, .6, .4, .3, .4, 1, .9, 1, .5, 2)
x=c(0, 0, 1, 1, 0, 0, 1, 1, 1, 1 )

xx=data.frame(id, x, y)

boot.cluster <- function(x, id){

  boot.id<http://boot.id> <- sample(unique(id), replace=T)
  out <- lapply(boot.id<http://boot.id>, function(i) x[id%in%i,])

  return( do.call("rbind",out) )

}

boot.pro<http://boot.pro>=boot.cluster(xx, xx$id)

Now I have the output

   id x   y
5   3 0 0.4
6   3 0 1.0
51  3 0 0.4
61  3 0 1.0
9   5 1 0.5
10  5 1 2.0
52  3 0 0.4
62  3 0 1.0
3   2 1 0.4
4   2 1 0.3

However, the id variable is the original id, while I want to take the new id as (1, 1, 2, 2, 3, 3, 4, 4, 5, 5) for later analysis. Can anyone show me how to do it? Of note, the same original id may have duplicates since the bootstrap sample is drawn with replacement. Thanks a lot!

Lei


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