Re: question about merge / lookup (was Re: statlist: offlist follow up)

["Michael Blasnik" <michael.blasnik@verizon.net>]

...
I don't understand how this merge is supposed to work -- it looks like a 
"many-to-many" merge because there is no unique set of key variables in either 
dataset.  I thought the proyeccion was supposed to be some population info, but 
then why does it have two entries for the values 0 2 2 for agegp dpto e1?

You need to come up with a way for Stata to determine which observations go 
together or you will end up with multiple matches.

Michael Blasnik

----- Original Message ----- 
From: "Sebastian Kruk" <residuo.solow@gmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Tuesday, July 17, 2007 1:30 AM
Subject: Re: question about merge / lookup (was Re: statlist: offlist follow up)



> Sorry Michael, I thought it was sent it by statalist. I have problems
> some weeks ago because I sent a message off-list.
>
> I have two datasets (a.dta and b.dta) as follows:
>
> a.dta
> agegp dpto e1 proyeccion
> 0 1 1 9261
> 1 1 1 36894
> 5 1 1 47986
> 0 1 1 48976
> 1 1 2 8863
> 5 1 2 35504
> 0 2 2 46194
> 1 2 1 47042
> 5 2 1 10401
> 0 2 2 4555
> 1 2 2 1543
> 5 2 2 519
>
> b.dta:
>
> agegp dpto e1 vaca0 vaca1
> 0 1 1 9261 6174
> 1 1 1 36894 24596
> 5 1 1 47986 31990
> 0 1 1 48976 32650
> 1 1 2 8863 5908
> 5 1 2 35504 23669
> 0 2 2 2133 455
> 1 2 1 2212 48971
> 5 2 1 108 1170
> 0 2 2 20 4304
> 1 2 2 238 566
> 5 2 2 2 72
> 0 1 1 9261 61
> 1 1 1 36894 245
> 5 1 1 47986 31
> 0 1 1 48976 3
> 1 1 2 8863 590
> 5 1 2 35504 236
> 0 2 2 213 455
> 1 2 1 221 48
> 5 2 1 108 11
> 0 2 2 2074 43
> 1 2 2 238 5
> 5 2 2 269 72
>
> I am trying to merge the two datasets such that the new dataset should read 
> as:
>
> agegp dpto e1 vaca0 vaca1 proyeccion
> 0 1 1 9261 6174 9261
> 1 1 1 36894 24596 36894
> 5 1 1 47986 31990 47986
> 0 1 1 48976 32650 48976
> 1 1 2 8863 5908 8863
> 5 1 2 35504 23669 35504
> 0 2 2 2133 455 46194
<snip>

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