Hi:

To get the samples, here's one approach:

df <- data.frame(gender = rep(c('F', 'M'), c(165, 42)), y = rpois(207, 20))
# Sampling function to take 20 F and 20 M with replacement
# The sample function operates on the rows of df to get idx and then takes
# the y's corresponding to those rows
sfun <- function(x) {
    idx <- c(sample(1:165, 20, replace = TRUE), sample(166:207, 20, replace
= TRUE))
    x[idx]
   }

# Replicate the process 1000 times
u <- t(replicate(1000, sfun(df$y)))
> dim(u)
[1] 1000   40

The first 20 rows are F, the second 20 M.

HTH,
Dennis

On Thu, Mar 10, 2011 at 1:04 AM, taby gathoni <tabieg@yahoo.com> wrote:

> Please note is with replacement
>
>
>
> From: taby gathoni <tabieg@yahoo.com>
> To: R help <r-help@r-project.org>
> Sent: Thursday, March 10, 2011 11:53 AM
> Subject: [R] random sampling steps in R
>
> Dear all,
>
> Could someone assist me in random sampling steps/code in R? I have a main
> sample  of  42 males and 165 females and I want to come up with about 1000
> samples of 20 males and 20 females from this main sample. While at it, i
> would also like to come up Accuracy  Ratios (ARs) with corresponding
> confidence intervals.
>
> Please assist.
>
>
> Thanks so much,
>
> Taby
>
>
>
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>
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> and provide commented, minimal, self-contained, reproducible code.
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@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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