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Re: st: sample size reduced significantly


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: sample size reduced significantly
Date   Fri, 12 Apr 2013 00:36:46 +0100

Values must be non-missing for all variables entered in a regression;
otherwise observations will be excluded. After your regression

. regress <whatever>

You can identify the excluded values

. gen excluded = !e(sample)

and then look for missings in the excluded

. egen nmissing = rowmiss(<whatever>) if excluded
. tab nmissing

Here <whatever> is whatever varlist you used for -regress-.

Nick
njcoxstata@gmail.com


On 11 April 2013 21:16, Yu Chen, PhD <profyuchen@gmail.com> wrote:

> I have several variables with each of them having at least 6000
> observations (non-missing values). However, when I put them into OLS
> regression, the number of observations reduced to only about 1000. I
> cannot figure out what causes the problem. Could you please help me
> find out the causes? What code can I use to analyze the problem?
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