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st: Creating a dummy variable under certain conditions


From   sebas nicaise <sebasnicaise@hotmail.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Creating a dummy variable under certain conditions
Date   Sat, 2 Jun 2012 12:06:27 +0000

Dear all,

 

I am struggeling with creating a new dummy variable. I have a very large (unbalanced) panel dataset that looks like this:

 

date gvkey viol
1997q1 1021 0
1997q2 1021 0
1997q3 1021 0
1997q4 1021 0
1998q1 1021 1
1998q2 1021 0
1998q3 1021 0
1998q4 1021 1
1999q1 1021 0

1999q2 1021 0

1999q3 1021 0
1999q2 1023 0
1999q3 1023 1
1999q4 1023 0
2000q1 1023 0
2000q2 1023 1


Where date is calender quarter, gvkey is the company identifier and viol a dummy which equals 1 if the firm is in violation of a covenant in a private debt contract.

 

The problem is that I have to create a new dummy variable ( new violation) which meets certain conditions.

The new violation dummy is only allowed to be 1 if in the previous 4 quarters of a certain company (gvkey) is 0. 

 

This means for example that:

 

date gvkey viol Newviolation
1997q1 1021 0       0
1997q2 1021 0       0
1997q3 1021 0       0
1997q4 1021 0       0
1998q1 1021 1       1
1998q2 1021 0       0
1998q3 1021 0       0
1998q4 1021 1       0
1999q1 1021 0       0

1999q2 1021 0       0

1999q3 1021 0       0
1999q2 1023 0       0
1999q3 1023 1       0
1999q4 1023 0       0
2000q1 1023 0       0
2000q2 1023 1       0

 

I do not know how to tell Stata to create this variable, Hope someone is so kind to help me.

 

Thank you,

Sebastiaan

  		 	   		  
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