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st: RE: Spotting changes in identifier


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Spotting changes in identifier
Date   Wed, 7 Jul 2010 12:12:09 +0100

You tried

bysort name: l name ticker year if ticker[_n]!="ticker[_n+1]"

but you need to omit the " ". What you typed is legal, but the literal text 

"ticker[_n+1]" 

presumably never is an actual value of -ticker-, so this will list all the data, as every value of ticker is indeed not equal to that text. 

As said, omit the "". 

Nick 
n.j.cox@durham.ac.uk 

Pavlos C. Symeou

I have panel data on a number of companies over a series of years. 
Two of my variables uniquely identify an observation (Name and 
Ticker). For different reasons:
a) the Name may have changed over the years whilst the Ticker may 
have remained the same;
year      name   ticker
1999    stata   ss
2000    strata ss

b) the Ticker may have changed over the years whilst Name may have 
remained the same;
year      name   ticker
1999    stata   ss
2000    stata   sss

c) both may have changed

year      name   ticker
1999    stata   ss
2000    strata sss


I am interested in identifying cases a) and b) above (considering 
that case c might require visual observation rather than an 
automated process)

Do you have any suggestions?

I have tried

bysort name: l name ticker year if ticker[_n]!="ticker[_n+1]"

but it doesn't seem to work. Both Name and Ticker are string variables.


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