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Re: st: Merge data for two panels in a panel data set


From   Eric Booth <eric.a.booth@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Merge data for two panels in a panel data set
Date   Mon, 26 Mar 2012 09:48:57 -0500

On Mar 26, 2012, at 9:35 AM, rado645-bg@yahoo.de wrote:

> Dear all,
> 
> I have two firms in a data set that merge at a given point of time. For a specific reason, I need to sum the observations over their balance sheet items in each period of time. Would that be possible in Stata? 
> 
> 
> The dataset looks like that:
> 
> Firm        Date    Item1    Item2    Item3
> 
> 
> Firm1     Date1   Item1    Item2    Item3
> 
> Firm2      Date1   Item1     Item2    Item3
> 
> Firm3      Date1  Item1    Item2     Item3
> 
> ...so on.
> 

 If you want to add across item1-item3, then:

egen sum = rowtotal(Item1-Item3) 

will do it. See -help egen-. 





> I would like to merge in each period of time the data for firm 1 and firm 2 so the dataset will look like that: 
> 
> 
> The dataset looks like that:
> 
> Firm                  Date     Item1  Item2  Item3
> 
> 
> Merged_Firms    Date1  Item1  Item2  Item3
> 
> Firm3               Date1  Item1  Item2  Item3
> 


I think you are asking how to -collapse- just Firms 1 and 2 in each year of your dataset.  This example would need to be expanded to account for the total # of Firms you have in your data and how you want to -collapse- them, but it reproduces your example table above:

**********
clear
inp firm date item1
1 2007 45
2 2007 50
3 2007 99
end

g collapseind = 1 if inlist(firm, 1, 2)
replace collapseind = 0 if mi(collapseind)

collapse (sum) item1, by(collapseind date)
lab def x 0 "Firm 3" 1 "Merged Firms"
lab val collapseind x
li
**********


-Eric


__
Eric A. Booth
Public Policy Research Institute 
Texas A&M University
ebooth@ppri.tamu.edu
+979.845.6754





> I would like to thank for your consideration in advance.
> 
> Best,
> Rado
> 
> 
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