R help - Oct 2007 - survey weights in sample with replacement

>> Hi,
       I am trying to draw a random sample from an household survey with sample
weight. Is there any function in R or Splus which allows this.
 
Regards,
 
*******************************************************
Mehtabul Azam
Department of Economics
Southern Methodist University
Dallas TX 75275-0496 
Tel: (214) 214 938 3906
Email: mazam at smu.edu <mailto:mazam at smu.edu> 
Web: http://people.smu.edu/mazam

On 31/10/07 4:03 PM, Azam, Mehtabul wrote:
>        I am trying to draw a random sample from an household survey with
sample weight. Is there any function in R or Splus which allows this.
I'm not sure if this what you're after, but R's pps package lets you
sample with probability proportional to size.

Hope this helps,
James
-- 
James Reilly
Department of Statistics, University of Auckland
Private Bag 92019, Auckland, New Zealand

On Tue, 30 Oct 2007, Azam, Mehtabul  wrote:
>>> Hi,
>       I am trying to draw a random sample from an household survey with 
> sample weight. Is there any function in R or Splus which allows this.
>
It depends on exactly what you want.

The sample() function will draw unequal probability samples with 
replacement.

sample() will also draw samples without replacement, but (as documented) 
it uses sequential sampling and so does not actually generate 
probabilities proportional to the specified weights for sample sizes 
greater than 1.

The error in sequential sampling is pretty small, but it has attracted a 
lot of creativity in the survey literature (probably more than it 
deserves).  The 'sampling' package implements several algorithms for 
drawing unequal probability samples without replacement that really are 
proportional to the specified weights where this is achievable.

 	-thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle