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st: match string variables


From   "Lukas Bösch" <L.Boesch@gmx.de>
To   statalist@hsphsun2.harvard.edu
Subject   st: match string variables
Date   Wed, 13 Apr 2011 23:18:52 +0200

Dear Stata Community.

I am working with the CITES trade data and my aim is to analyze the export of 130 countries from 1990 to 2009 with a logistic model. CITES regulates the international trade in endangered species. The export data for Afghanistan, for example, looks like this:

year       taxon          term       unit        country         value
   
1990      Falco Cherrug   live         -            AF              0
1991      Falco Cherrug   live         -            AF              0
1992      Falco Cherrug   live         -            AF              0
1993      Falco Cherrug   live         -            AF              0

In the case of Afghanistan, the data contains 180 rows, with nine different taxon. In some cases it contains up to 8000 rows with 2000 taxon. I know that I could also have shown the data in a wide form with much fewer rows... 

Now I want to create a variable “indigenous” with 1 if the exported taxon exists in the country or 0 if not. In order to get this I copied the species lists for all 130 countries from the CITES homepage, which looks like this (again for Afghanistan):

Accipiter badius (Gmelin, 1788)
Accipiter gentilis (Linnaeus, 1758)
Accipiter nisus (Linnaeus, 1758)
Acinonyx jubatus (Schreber, 1775)
Acipenser nudiventris Lovetzky, 1828

This list contains 131 taxon and I sorted it out in order to get rid of the years, the commas and so on.

Accipiter badius
Accipiter gentilis
Accipiter nisus
Acinonyx jubatus
Acipenser nudiventris Lovetzky

I have tried different variations of merge and joinby, I looked at the ado files _gsoundex, nearmrg, nmatch and reclink but I haven’t been able to create the “indigenous” variable so far.
There are two major problems. The first one is that the taxon in the species list doesn’t always match exactly with the taxon in the export data. For example, Falco cherrug, in the export data is listed as Falco Cherrug Gray in the species list. The second problem is that the species list has a different number of observations than the export data and they dont fit logically together. 
I need something like: If the taxon from the export data is on the species list, then “indigenous” = 1, if the taxon from the export data is not on the species list, then “indigenous” = 0. 

Maybe someone has an idea and can give me a hint on how to do this.

Thank you very much

Lukas

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