Re: [R] Fw: random sampling steps in R with replacement

From: Dennis Murphy <djmuser_at_gmail.com>
Date: Thu, 10 Mar 2011 05:34:43 -0800

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_at_yahoo.com> wrote:

> Please note is with replacement
>
>
>
> From: taby gathoni <tabieg_at_yahoo.com>
> To: R help <r-help_at_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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>
>
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> ______________________________________________
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> PLEASE do read the posting guide
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>

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