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From |
"Jitian Sheu" <jtsheu@bu.edu> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: Re: -Sample-, but each observation has irregular # of rows |

Date |
Tue, 25 Nov 2003 21:06:30 -0500 |

One way to do this is to use the following method: suppose you only want to sample 100 ids from them(you can easily change the method to fit your sampling criteria) sort id by id: gen n=_n sort n id gen tmp=uniform() if n==1 sort n tmp gen tmpx=. by n : replace tmpx=_n gen sampledid=1 if n==1& tmpx<=100 gen xid=. sort id sampleid by id: replace xid=sampleid[1] keep xid==1 this should works jt ----- Original Message ----- From: "Chih-Mao Hsieh" <hsieh@wustl.edu> To: <statalist@hsphsun2.harvard.edu> Sent: Tuesday, November 25, 2003 8:37 PM Subject: st: -Sample-, but each observation has irregular # of rows > Hello all, > > > I have a dataset from which I have to sample. For each observation > ("ID" in table below), there are multiple rows. And the number of rows > is irregular per ID. My problem: I want to be able to sample ID's from > the dataset. Say the dataset has 3 ID's like the following: > > ID x y var1 var2 > 001 3 4 5 3 > 001 3 5 7 6 > 001 4 5 2 3 > 002 2 4 1 5 > 003 1 2 9 11 > 003 1 3 6 2 > 003 1 4 9 5 > 003 2 3 10 2 > 003 2 4 7 4 > 003 3 4 6 12 > > If I sample 1 ID and get #001, I want to get all of #001's 3 rows. Of > course, I am aware of the working man's solution: collapse by(id), > sample, merge back to original, keep _merge==3. But this seems > inefficient. I've searched the Statalist and "search sample" in STATA > 8, but to no avail. Is there not an easier way to do what I need? > > > Thanks in advance, > Chihmao > > * > * 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/ > * * 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/

**References**:**st: -Sample-, but each observation has irregular # of rows***From:*"Chih-Mao Hsieh" <hsieh@wustl.edu>

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