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st: using information from value label to generate new variables


From   Evelyn Ersanilli <evelyn.ersanilli@qeh.ox.ac.uk>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: using information from value label to generate new variables
Date   Thu, 7 Jun 2012 16:55:21 +0000

Dear Statalisters,

I'm having some problems getting a macro to function properly.

I have a cross-sectional survey dataset. 
For question "a", people were asked to list up to 9 countries.
All variables a1-a9 (numeric, up to 3 digits) have the same value label; "locations".
Because it also attached to other variables, the value label locations does not only hold the 3 digit country codes, but also 5-digit regional codes.

For each country (eg France, Germany, Zimbabwe, etc) that was mentioned I would like to generate a variable that is  0 if that country has not been named as any of the 9 replies (many people gave fewer than 9 replies) by a respondent, and 1 if the country has been named as any of the up to 9 replies by a respondent (and missing if the respondent didn't answer a1-a9).
These variables should have the names of the country.

Building on online examples I've gotten close to what I want, but I have problem correctly & efficiently delimiting the list of newly generated variables.
I first tried to get the values and labels from the first answer (a1). However this risks omitting countries that have only been named in a2,a3 etc.
In my second attempt I therefore tried to abstracts the values and labels from the value label 'locations' using labellist and r()
The problem with Attempt 2 is that r() only saves up to (244?) characters, which is fewer that all values together and I haven't found out how to increase the storage capacity.
Ideally I would also limit the abstraction of lables&values to only the 1-3digit country codes., leaving out the 5-digit regional codes.

Any alternative suggestions  would be welcome


Here is my syntax:


*-------------------Attempt I-----------
//Step 1: abstract labels
levelsof a1, local(a1_levels)        
    foreach val of local a1_levels {   
    local c`val' : label locations `val'  
    }
macro list

//Step 2: generate dummies
foreach X of local a1_levels {  
egen var`X'=anymatch(a1 a2 a3 a4 a5 a6 a7 a8 a9), values(`X')
}  

//Step 3: label and rename
local variablelist "var"
foreach variable of local variablelist{     
	foreach value of local a1_levels{     
	label variable `variable'`value' "`c`value''"
	local stringy =strtoname("`c`value''")		//needed because some country names contain spaces or other illegitimate characters
	rename `variable'`value' `stringy'
	}
}
*-----------------------------------------

*-------------------Attempt II-----------
//Step 1: abstract labels
quietly: labellist locations
local loc_levels= r(locations_values)
	foreach val of local loc_levels {   /* loop over all values in local list `var'_levels */
    local c`val' : label locations `val'  /* create macro that contains label for each value */
    }
macro list
//etc
*-----------------------------------------





For step 2 I've also tried:
*-----------------------------------------
foreach X of numlist 2/935 {  
	egen var`X'=anymatch(a1 a2 a3 a4 a5 a6 a7 a8 a9), values(`X')
			}  
*-----------------------------------------
But that generates way too many variables as many of the values between 2 and 935 do not have a country code associated with it.
I could of course just look up all the value that were assigned a label in locations, but where's the fun in that..



Kind regards


Evelyn

Departmental Lecturer
Oxford Department of International Development (QEH)
International Migration Institute
University of Oxford
3 Mansfield Road
Oxford OX1 3TB
United Kingdom
Tel: +44 (0)1865 281717

http://www.eumagine.org
http://www.migration.ox.ac.uk


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