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From |
"Conner Mullally" <mullally@primal.ucdavis.edu> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
st: 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 * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

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