[R] Generating unordered, with replacement, samples

[Giovanni Petris]

Thank you, Rui, but I have the feeling that in this way you are drawing uniformly *ordered* samples, and you get a bias if you consider them to be unordered.

Best,
Giovanni

________________________________________
From: Rui Barradas [ruipbarradas at sapo.pt]
Sent: Wednesday, September 17, 2014 13:49
To: Giovanni Petris; r-help at R-project.org
Subject: Re: [R] Generating unordered, with replacement, samples

Hello,

Try function ?sample. Something like, if 'x' is a vector of size n,

sample(x, k, replace = TRUE)

If you want indices into 'x', try instead

sample(n, k, replace = TRUE)

Hope this helps,

Rui Barradas

Em 17-09-2014 19:25, Giovanni Petris escreveu:
>
> Hello,
>
> I am trying to interface in my teaching some elementary probability with Monte Carlo ideas. In sampling from a finite population, the number of distinct samples of size 'k' from a population of size 'n' , when individuals are selected with replacement and the selection order does not matter, is choose(n + k -1, k). Does anyone have a suggestion about how to simulate (uniformly!) one of these possible samples? In a Monte Carlo framework I would like to do it repeatedly, so efficiency is of some relevance.
>
> Thank you in advance!
>
> Best,
> Giovanni
>
>
>
> Giovanni Petris
> Associate Professor
> Department of Mathematical Sciences
> University of Arkansas - Fayetteville, AR 72701
> Ph: (479) 575-6324, 575-8630 (fax)
> http://definetti.uark.edu/~gpetris/
>
>
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