Re: st: RE: merging - unique observations

["Joseph Coveney" <stajc2@gmail.com>]

Make sure that you get the m:1 or 1:m in the proper order.  If not, then you'll get the error you mentioned.  See below.

Joseph Coveney

. clear *

. set more off

. set linesize 79

. 
. input str244(reporter partner) int period str2 trade

                                                                               
>                                                                              
>                                                                              
>         reporter                                                             
>                                                                              
>                                                                              
>                         partner    period      trade
  1. can usa 2000 k1
  2. can usa 2002 k2
  3. end

. 
. tempfile tmpfil0

. quietly save `tmpfil0'

. 
. drop _all

. 
. input str244(reporter partner) str2 distance

                                                                               
>                                                                              
>                                                                              
>         reporter                                                             
>                                                                              
>                                                                              
>                         partner   distance
  1. can usa x1
  2. can arg x2
  3. end

. 
. *
. * Accidentally got it backwards (gives error message)
. *
. capture noisily merge m:1 reporter partner using `tmpfil0'
variables reporter partner do not uniquely identify observations in the using
    data

. 
. *
. * Got it right, here
. *
. merge 1:m reporter partner using `tmpfil0', ///
>     keep(matched) noreport nogenerate

. 
. sort reporter partner period

. list, noobs sepby(reporter partner)

  +------------------------------------------------+
  | reporter   partner   distance   period   trade |
  |------------------------------------------------|
  |      can       usa         x1     2000      k1 |
  |      can       usa         x1     2002      k2 |
  +------------------------------------------------+

. 
. exit

end of do-file

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Andreas Dimopoulos
Sent: Sunday, April 6, 2014 13:34
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: RE: merging - unique observations

My first dataset is like:

reporter partner period trade
can       usa      2000   k1
can       usa      2002   k2

and my second dataset is like:

reporter partner  distance
can        usa     x1
can        arg     x2

A difference between the datasets is that the second one has every pair of
countries in the sample while the first one not. For example, the pair
CAN-ARG does not exist in the first one. Hope that helps?

Regards,
A


On Sun, 6 Apr 2014 00:35:33 +0000, Joe Canner <jcanner1@jhmi.edu> wrote:
> Andrew,
> 
> It is difficult to say for sure what the problem is without more details
> about your data, what command(s) you ran, and the exact error message
you
> received.
> 
> However, it appears that at least one of the problems is that your first
> data set has multiple observations per country-pair (one for each year)
> while the second data set has only one observation per country-pair.  If
> this is the case, try a many-to-one merge:
> . merge m:1 countrypair using distancedata
>  
> I can also imagine other problems that might arise from the use of
> country-pairs as the merging key, but we would have to know more about
your
> data in order to diagnose them.
> 
> Regards,
> Joe Canner
> Johns Hopkins University School of Medicine
> 
> ________________________________________
> From: owner-statalist@hsphsun2.harvard.edu
> [owner-statalist@hsphsun2.harvard.edu] on behalf of Andreas Dimopoulos
> [ad382@sussex.ac.uk]
> Sent: Saturday, April 05, 2014 5:47 PM
> To: statalist@hsphsun2.harvard.edu
> Subject: st: merging - unique observations
> 
> Good evening,
> 
> I have two datasets where the first one contains pairs of countries and
> their in between trade for different years and another dataset which has
> the pair of countries and their in between distance etc (which don't
change
> over time). I tried to merge those two datasets based on the things I
have
> read but stata tells me that the observations cannot be uniquely
> identified.
> 
> Any piece of advise?
> 
> Regards,
> Andrew
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