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
[email protected] | p: (202) 238-3576
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Stefano Bonini
Sent: Wednesday, June 10, 2009 6:18 PM
To: [email protected]
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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