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RE: st: Creating a data subset with subjects chosen at random


From   Amal Khanolkar <Amal.Khanolkar@ki.se>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: Creating a data subset with subjects chosen at random
Date   Fri, 15 Jun 2012 14:03:28 +0000

Thanks Brendan,

It worked perfectly  :)

Just a question: 

in the command line: by cbirth: 

gen subsamp = _n <= (_N+0.5)*0.05

0.05 specifies 5% proportion right?


Regards,

/Amal.

From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Brendan Halpin [brendan.halpin@ul.ie]
Sent: 15 June 2012 15:29
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Creating a data subset with subjects chosen at random

On Fri, Jun 15 2012, Amal Khanolkar wrote:

> - I would like to create a subset of the above dataset that consists of
> 1. 100,000 subjects, 2. With the same distribution of subjects by
> country of origin as above in the parent dataset. 3. Tell Stata to
> choose the subjects at random. The dataset of course has several other
> variables. But I would like to define the new data subset based on the
> above country of origin as it is my main exposure variable.

Something like this

// create random variable
gen x = runiform()

// sort by country and x
sort cbirth x

// create a variable within country identifying the first 5% (change
// this proprtion as you wish)

by cbirth: gen subsamp = _n <= (_N+0.5)*0.05

tab cbirth subsamp, col

tab cbirth sex if subamp


Regards,

Brendan
--
Brendan Halpin,   Department of Sociology,   University of Limerick,   Ireland
Tel: w +353-61-213147  f +353-61-202569  h +353-61-338562;  Room F1-009 x 3147
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http://teaching.sociology.ul.ie/bhalpin/wordpress         twitter:@ULSociology
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