[R] Resampling question

[Nordlund, Dan (DSHS/RDA)]

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Vikram Chhatre
> Sent: Thursday, May 10, 2012 4:57 PM
> To: r-help at r-project.org
> Subject: [R] Resampling question
> 
> Hello -
> 
> I have a population of 100 individuals that I would like to bootstrap
> 10 times, every time removing 5 *different* individuals.
> 
> So far, I have done the following:
> 
> pop <- read.table('mypop.txt', header=FALSE)
> 
> replicate(10, sample(pop, 95, replace=FALSE))
> 
> I have not actually gone through each of the 10 files created to make
> sure no single individual was removed more than once during the 10
> bootstraps.  But will the above syntax achieve this object?
> 
> Thanks
> V

What you are doing is probably more appropriately called a jack-knife, rather than bootstrap.  Be that as it may, your approach will not prevent someone being dropped more than once.  You might randomly select 50 people without replacement and then drop them 5 at a time from the original population

to_drop <- sample(100,50,replace=FALSE)
rep1 <- pop[-to_drop[1:5],]
rep2 <- pop[-to_drop[6:10],] 
...

I will let you decide how you want automate this.

Dan


Daniel J. Nordlund
Washington State Department of Social and Health Services
Planning, Performance, and Accountability
Research and Data Analysis Division
Olympia, WA 98504-5204