Re: st: STATA Question: drop command with several conditions

[Roberto Liebscher <roberto.liebscher@ku.de>]

Why not generate a variable that gives the number of non-missing (and 
non-zero) observations for the years 2007 and 2008 for each firm? Then 
you can use this variable for the drop command.
*Markcap of 0 to missing
replace markcap = . if markcap == 0

*Count observations that are non-missing in years 2007 and 2008
bysort firm: egen countvar = count(markcap) if year == 2007 | year == 2008

*Copy constant to other years
bysort firm: egen countvar2 = min(countvar)

*Delete observations
drop if countvar2 < 2 //If I got you right, you want to keep all 
observations with at least one non-missing (or non-zero) observation in 
2007/2008
HTH,
Roberto

--
Roberto Liebscher
Catholic University of Eichstaett-Ingolstadt
Department of Business Administration
Chair of Banking and Finance
Auf der Schanz 49
D-85049 Ingolstadt
Germany
Phone:  (+49)-841-937-1929
FAX:    (+49)-841-937-2883
E-mail:   roberto.liebscher@ku-eichstaett.de
Internet: http://www.ku.de/wwf/lfb/



Am 22.03.2014 13:33, schrieb Julian Kochan:
> Hi,
>
> i have a set of data with financial firm characteristics of about 10.000 firms for Year 2000 - Year 2012.
>
> Let's assume: The first column of the data table displays the Name of the firm, the second the Year and the third displays the Market Capitalization.
> Thus, 13 rows in a row (2000-2012) display information about just one firm - just the year varies.
>
> Problem: I want to drop those firms, for which the Market Cap is zero or Missing in the Year 2007 or Year 2008.
> 		 If this is the case, the firm should be dropped out of my data completely such that the firm observation is not only dropped for 2007 and 2008, but also for all the other year.
> 		 I tried a lot but it didn't succeed. As you can see the condition is based on 3 Variables ( firm, market Cap and Year).
>
> I would be really really happy to receive an answer.
>
> best regards
>
> Julian
>
>
>
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