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

[Steven Samuels <sjhsamuels@earthlink.net>]

-
Take the second -set seed- outside the loop. That will prevent the  
generation of the same random numbers. I cannot dissect the rest of  
your code, but it looks like you are generating overlapping pairs in  
`j': (1,2), (2,3), (3,4). Also, what happens if there is an odd  
number of observations within a cluster?

Steve

On May 5, 2008, at 12:31 PM, Conner Mullally wrote:


> 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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