RE: st: RE: Requirement(s) for a match merge

["louis boakye-yiadom" <louisby@hotmail.com>]

Perhaps an example will clarify my concern. Suppose we have the following 
datasets, where -id- (the identifier) represents family code:
Dataset1
     id   father
1.   1    John
2.   2    Peter
3.   3    Sam

Dataset2
    id  child
1.  1   Bill
2.  2   Joe
3.  2   Mary
4.  3   Phil
5.  3   Sue
6.  3   Pat

I was thinking that even though -id- does not uniquely identify each 
observation in dataset 2, the datasets can still be merged using -id- as the 
match variable to obtain a result like the following:

    id   father child
1.  1    John   Bill
2.  2    Peter  Joe
3.  2    Peter  Mary
4.  3    Sam    Phil
5.  3    Sam    Sue
6.  3    Sam    Pat

Or is it that this kind of merge is not called match merge? Thanks.

Louis



> From: "Nick Cox" <n.j.cox@durham.ac.uk>
>
> Let's turn this round. If this is not true,
> how do you expect match merge to work?
>
> Nick
> n.j.cox@durham.ac.uk
>
> louis boakye-yiadom
>
> > Is it true that "for a match merge to work, the identifier or
> > identifiers
> > must uniquely identify each observation"? I found this
> > statement in sample
> > lecture NC 101 (one of StataCorp's NetCourses), but I thought
> > that this
> > requirement (of the id uniquely identifying each observation)
> > is often
> > desirable, but not necessary in all cases. Any insights will
> > be appreciated.

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