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st: egen or other methods to calculate consecutive row totals?


From   Alexandra de Montrichard <ademontr@attbi.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: egen or other methods to calculate consecutive row totals?
Date   Mon, 03 Mar 2003 14:08:32 -0500

I am somewhat new to stata and I need some help with a problem I can't seem to resolve.

I am working with a database of students for whom I have quarterly grades for 5 years (1995-2000). I also have the start & completion date for a class that all students took a one point during those five year. I need to figure out how many quarters of grades I have for each student before & after they took this class & how many are consecutive quarters of grades. I've created a 0-1 variable for each quarter (0 if the student did not get any grades that quarter, 1 if they received a grade), converted the class start & exit date into quarter format & used egen to count of the number of quarters in which each student received grades
. egen byte gradenbr = neqany (grade951-grade004), v (1)
However, I now need to figure out a way of counting the number of quarters with grades both before & after the class as well as a way to know how many consecutive quarters with grade I have after completion of the class. I though I could use egen combined with if to create a gnbrpost variable of the number of quarters with grades after completion of the class:
. egen byte gnbrpost = neqany (grade951-grade004) if (exitdq== q(1995q1)), v (1)
. egen byte gnbrpost = neqany (grade952-grade004) if (exitdq== q(1995q2)), v (1)
. egen byte gnbrpost = neqany (grade953-grade004) if (exitdq== q(1995q3)), v (1) etc.....

but I can't figure out how to replace the gnbrpost variable each time I run a new egen calculation plus I'm sure there must be a better way of doing this, which would also allow me to know how many consecutive quarters of grades I have.

Thanks!
Alexandra de Montrichard


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