From: Jorge Ivan Velez <jorgeivanvelez_at_gmail.com>

Date: Thu, 03 Jun 2010 12:21:35 -0400

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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. Received on Thu 03 Jun 2010 - 16:24:51 GMT

Date: Thu, 03 Jun 2010 12:21:35 -0400

# Option 1

d <- data.frame(x, t)

y <- with(d, ifelse(t == 0, rbinom(2, 1, 0.2), rbinom(3, 1, 0.8)))
y

# Option 2 -- more general case, e.g. you do not know
# how many 0's and 1's you have within each strata
spd <- with(d, split(d, x))

do.call(c, lapply(spd, function(comp)

with(comp, ifelse(t == 0, rbinom(sum(t==0), 1, 0.2),rbinom(sum(t!=0), 1, 0.8)))))

**HTH,
**

Jorge

On Thu, Jun 3, 2010 at 11:49 AM, Carrie Li <> wrote:

> Dear R-helpers,

*>
**> I would like to generate a binary random variable within a stratum's
**> stratum. Here is a simple example.
**>
**>
**> ## x is the first level strata index, here I have 3 strata.
**> x=c(rep(1,5), rep(2,5), rep(3,5))
**>
**> ## within x, there is a second strata indexed by t=0 and t=1
**> t=rep(c(0,0,1,1,1),3)
**>
**>
**> ## and within strata i and t=0 and t=1, I generate the random binomial
**> variable respectively, and save in y
**> y=rep(NA, length(x))
**> for (i in 1:3)
**> {
**> y[(x==i)&(t==0)]=rbinom(2, 1, 0.2)
**> y[(x==i)&(t==1)]=rbinom(3, 1, 0.8)
**> }
**>
**>
**> My question: is there any way to avoid the for loop, since I have the first
**> level strata has thousands of strata. (Within each x stratum, the t only
**> has
**> 2 levels, 0 and 1 )
**>
**> Thanks for any help!
**>
**> Carrie
**>
**> [[alternative HTML version deleted]]
**>
**> ______________________________________________
**> R-help_at_r-project.org mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide
**> http://www.R-project.org/posting-guide.html
**> and provide commented, minimal, self-contained, reproducible code.
**>
*

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