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st: RE: error checking

From   "Nick Winter" <>
To   <>
Subject   st: RE: error checking
Date   Wed, 25 Sep 2002 17:23:08 -0400

> -----Original Message-----
> From: Riano, Alejandro [] 
> Sent: Wednesday, September 25, 2002 5:02 PM
> To:
> Subject: st: error checking
> I have a huge industrial survey which is a panel dataset. I 
> have the id of
> the each firm and the region in which this firm is based. I'd 
> like to check
> how many of the firms  in this dataset have errors in the 
> sense that the
> same id would be associated with a different region and/or 
> that a given firm
> would have different year of foundation. (to have an idea of 
> the % of errors
> in the database);
> I also want to know which ones are the "problematic" firms.

This should do it:

bysort firm (region): gen problem=!(region[1]==region[_N])

The logic here is that in a list sorted by region within firm, the first
and last records for a firm will be equal if and only if all records fro
the firm are in the same region.  
With the dataset sorted by region within firm, this generates a variable
called problem, which equals zero if this holds, or one if not.

Then you can -tabulate-, -list-, or do whatever with th eproblem

Nick W

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