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st: Re: reproducing results of a random number generation within a loop using seed


From   "Conner Mullally" <mullally@primal.ucdavis.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re: reproducing results of a random number generation within a loop using seed
Date   Mon, 05 May 2008 12:57:14 -0500

Never mind.  I'm still not sure why my original code didn't
work, but I used the following instead:

levelsof cluster, local(ctlevels)
foreach i of local ctlevels {
qui su id3 if cluster==`i'
forvalues j=1(2)`r(max)' {
qui replace pair=`j' if $cluster==`i'&id3==`j'
qui replace pair=`j' if $cluster==`i'&id3==(`j'+1)
}
}
bysort cluster pair: g random=uniform()
sort cluster pair random
by cluster pair: g id4=_n
qui replace invite=1 if id4==1
qui replace invite=0 if id4==2

thanks to anyone who spent any time on this.

----- Original Message Follows -----
From: "Conner Mullally" <mullally@primal.ucdavis.edu>
To: statalist@hsphsun2.harvard.edu
Subject: Re: reproducing results of a random number
generation within a loop using seed
Date: Mon, 05 May 2008 11:31:02 -0500

> If I can follow up my own question, I looked harder at my
> results, and the loop is generating the same two random
> numbers for each pair, but it is switching who received
> which number within each pair.  Is there anyway I can keep
> this from happening?
> 
> ----- Original Message Follows -----
> From: "Conner Mullally" <mullally@primal.ucdavis.edu>
> To: statalist@hsphsun2.harvard.edu
> Subject: reproducing results of a random number generation
> within a loop using seed
> Date: Mon, 05 May 2008 10:44:10 -0500
> 
> > Hello,
> > I am trying to generate random numbers in a way that can
> > be replicated later (I am drawing random samples), and
> > having some trouble. I have two steps in my program.
> > First , I collapse the data set by group and randomly
> > select groups using the following code:
> > collapse $numvarssector, by($cluster)
> > set seed 54234
> > generate randomc=uniform()
> > sort randomc
> > g id2=_n
> > g ctreat=.
> > replace ctreat=1 if id2<=13
> > replace ctreat=0 if id2>13
> > sort cluster
> > drop randomc
> > 
> > I have no problem replicating the results of this step.
> > Next, after merging the grouped data with the individual
> > data, so that each person now has a variable "ctreat"
> > which indicates whether or not he or she is in a
> > treatment group, I draw random samples from within each
> > treatment group. What I want to do is the following:
> > order each observation within the groups by the size of
> > a continuous variable, "farm." Then, I want to break the
> > observations into nearest neighbor pairs using this
> > variable, and randomly assign one person from each pair
> > to the treatment group: sort cluster farm
> > by cluster: g id3=_n
> > sort $cluster id3
> > g invite=.
> > levelsof cluster, local(ctlevels)
> > foreach i of local ctlevels {
> > qui su id3 if cluster==`i'
> > forvalues j=1(2)`r(max)' {
> > set seed 54234
> > qui generate random`j'`i'=uniform() if
> > id3==`j'&$cluster==`i'|id3==(`j'+1)&$cluster==`i'
> > sort random`j'`i'
> > drop random`j'`i'
> > qui g d`j'_`i'=_n if
> > id3==`j'&cluster==`i'|id3==(`j'+1)&cluster==`i'
> > qui replace invite=1 if d`j'_`i'==1
> > qui replace invite=0 if d`j'_`i'==2
> > drop d`j'_`i'
> > }
> > }
> > 
> > I get a different sample every time I do this. Note that
> > I have already dropped the groups with ctreat==0 before
> > doing this step. Am I setting the seed in the wrong
> > spot? Or perhaps there is a better way to do this that I
> > am not seeing...
> > Thanks in advance
> > Conner
> > 
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