RE: st: RE: Unbalancing a panel data set with country pairs

[Nick Cox <n.j.cox@durham.ac.uk>]

<sacrifice> 

. search identifier 

points you to useful information. In this case, 

egen idnew = group(id1 id2), label 

is one of the easiest solutions. There is also a miniature review of possibilities at 

SJ-7-4  dm0034  . . . Stata tip 52: Generating composite categorical variables
        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
        Q4/07   SJ 7(4):582--583                                 (no commands)
        tip on how to generate categorical variables using
        tostring and egen, group()

but the help to -egen- -- which I did refer you to earlier -- contains enough to solve this problem. 

Nick 
n.j.cox@durham.ac.uk 

Matei Frunzetti

Thank you for your timely answer and excuse me for not being clear  
enough: my main problem is that the country pairs have a single id for  
each country, so i need to introduce a new id with its values being  
unique identifiers for the respective country pairs such that i can  
use by etc.

ex:
id1   id2    idnew  var1 ...

cty1  cty2   pair1  234
cty2  cty1   pair2  456

I am aware that this must seem pretty banal but i simply cannot find a  
thread or help that would adress this problem, I probably just don't  
know where to look.

Zitat von Nick Cox <n.j.cox@durham.ac.uk>:

> I assume that "country pair" defines a panel identifier.
>
> Look at the help for -egen-, which gives you one way to start.
>
> In terms of missings,
>
> egen missing_in_obs = rowmiss(varlist)
> egen missing_in_panel = total(missing_in_obs), by(panelid)
> drop if missing_in_panel
>
> In terms of not enough years, you don't quite say what the time  
> resolution of your data is. But assuming you have yearly  
> observations then
>
> bysort panelid : drop if _N < 17
>
> drops the short panels. If it's half-years, quarters, months, etc.  
> adjust as needed.
>
> You need to plug in your own <varlist> and <panelid>.
>
> The big concept you appear to be missing is that of working -by:-.  
> There is a tutorial at
>
> SJ-2-1  pr0004  . . . . . . . . . . Speaking Stata:  How to move  
> step by: step
>         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   
> N. J. Cox
>         Q1/02   SJ 2(1):86--102                                  (no  
> commands)
>         explains the use of the by varlist : construct to tackle
>         a variety of problems with group structure, ranging from
>         simple calculations for each of several groups to more
>         advanced manipulations that use the built-in _n and _N
>
> Nick
> n.j.cox@durham.ac.uk
>
> Matei Frunzetti
>
> I 'm working on a panel data set over 17 years. It's fairly unbalanced
> und i need to drop all observations for country pairs that either lack
> full length (as in years) or have missings in one of the independant
> variables. The problem is that i have to delete all observations of
> these country pairs for all years if only one or more variables have a
> missing or if it is one or more years short. I ran into a dead end
> trying to figure out how to imply the rest of the observations of a
> "faulty" country pair into the drop command.

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