Re: st: drop observations within groups under certain conditions

[Richard Goldstein <richgold@ix.netcom.com>]

I would do this in a couple of steps:

gen byte pos=earnings>0 & earnings<.
egen byte totpos=total(pos), by(manager_ID)
keep if totpos>1
drop totpos pos * unless of course you want to keep these

Rich

On 6/28/13 8:42 AM, Nahla Betelmal wrote:
> Dear Statalist,
> 
> my data in focus represnts three variables : manager ID (uniqe(,
> tenure period (which varies among managers) and earnings (which could
> be positive, zero, negative, or missing).
> 
> I want to keep only the managers who have positive earnings at least
> twice (at least for two years). To be more clear I want to keep all
> the observations for the manger who has positive earnings at least
> twice, regardless if in the other years he has non-positive earnings.
> 
> In other words I want to drop managers who have no positive earnings
> at all, or positive earnings once during his tenure period.
> 
> I thought of a command such as : by manager_ID year keep if earnings >
> 0.  However, this command has two problems: I do not know how to
> specify "at least twice" occurrence condition (i.e. earning is
> positive at least twice during manager tenure years) and it  will drop
> other year-observations for the same manger who has mix range of
> earnings!
> 
> For example, I would like to keep all the observation for manager
> A123, and drop all of those of Manger B567
> 
> 
> year  manager_ID earnings
> 1995   A123            + 12
> 1996   A123            + 4
> 1997   A123               0
> 1998   A123              -3
> 1999   A123               .
> 
> 1997   B567            + 5
> 1998   B567             -2
> 1999   B567              .
> 
> Thank you
> 
> Nahla Betelmal
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/faqs/resources/statalist-faq/
*   http://www.ats.ucla.edu/stat/stata/