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st: RE: RE: dropping observation


From   Howard Lempel <HLempel@brookings.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: dropping observation
Date   Wed, 10 Jun 2009 18:49:46 -0400

//

This should have been:

bysort analystID: egen Demp = mdev(employerID)
drop if Demp==0

Howie Lempel
Research Assistant
The Brookings Institution | Economic Studies
 
1775 Massachusetts Ave NW | Washington DC 20036
hlempel@brookings.edu | p: (202) 238-3576
 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Howard Lempel
Sent: Wednesday, June 10, 2009 6:40 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: dropping observation

Not sure if this is the most efficient way, but:

******* Begin example ********
/*
 Create a variable with the mean absolute deviation from the mean of employer ID for each analyst.  This will be 0 if the employer ID never changes.
*/
by analystID: egen Demp = mdev(employerID)

// Drop observations where the employer ID never changed.
drop if Demp==0
****** End Example **********

Hope this helps.
Howie

Howie Lempel
Research Assistant
The Brookings Institution | Economic Studies
 
1775 Massachusetts Ave NW | Washington DC 20036
hlempel@brookings.edu | p: (202) 238-3576
 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Stefano Bonini
Sent: Wednesday, June 10, 2009 6:18 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: dropping observation

Hi
I have a huge panel dataset containing analyst forecasts. Each analyst is associated with an employer. Sometimes analyst change employer. I want to restrict my dataset, dropping the observations of analysts that never change employer. The dataset may look like this

forecast#     analystID   employer ID
1                 1            1
2                 1            1
3                 1            1

1                 2            1
2                 2            1
3                 2            2
4                 2            2

1                 3            3
2                 3            4

In this case I'd nee to drop all observations by analyst 1 because he never changes employer, while keeping those of analysts 2 and 3.

I really cannot figure out the way to do it as visual inspection is just impossible with over 1.2m obs.

Thanks!

Stefano
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