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loopsstatacapturestata-macros
Timo K
Timo K

Reputation: 29

Keep a list of variables when some variables don't exist

For several countries, I have one dataset and I want to keep a list of variables (specified in a global vlist) for each of them. Some variables do not exist in some countries.

I want Stata to ignore the non-existence of these variables and execute the keep command for the rest of the variables. However, the problem is the additional for loop on the country-level, that I'm struggling to incorporate.

This question is similar to the one asked in these threads:

Ultimately, I want to end up with a dataset for each country that has only those variables specified in the vlist (minus the ones from the vlist that do not exist).

Here's the code, which is mostly taken from the thread above:

clear all
set obs 5

local vlist v0 v1 v2 v3 v4 v5

foreach v of local vlist { 
    generate `v' = runiform()
}

save country1.DTA, replace
save country2.DTA, replace
save country3.DTA, replace

global vlist_example v0 v1 v6          // v6 is not part of the dataset

foreach country in country1 country2 country3 {
   local keeplist = ""
      foreach i of global vlist_example {
          capture confirm variable `i'
              if !rc {
                  local "`keeplist' `i'"
          }
      }
keep `keeplist'     
save `country'beta2.DTA, replace 

}

However, this produces the following error:

rc not found
r(111);

I hope this sufficiently describes my problem, but please let me know if anything needs more explaining.

Upvotes: 0

Views: 1078

Answers (2)

user8682794
user8682794

Reputation:

The main problem with your code is that you do not call each dataset to modify it accordingly.

The following should give you what you want:

clear all
set obs 5

local vlist v0 v1 v2 v3 v4 v5

foreach v of local vlist { 
    generate `v' = runiform()
}

save country1, replace
save country2, replace
save country3, replace

global vlist_example v0 v1 v6          // v6 is not part of the dataset

foreach country in country1 country2 country3 {
    use `country'.dta, clear
    local keeplist ""
    foreach i of global vlist_example {
        capture confirm variable `i'
        if !_rc {
            local keeplist "`keeplist' `i'"
        }
    }
    keep `keeplist'     
    save `country'beta2, replace 
}

Note that after capture you need to type !_rc and not !rc.

Upvotes: 1

Nick Cox
Nick Cox

Reputation: 37183

That's an exercise in finding the intersections of various lists of names. 

local wanted v0 v1 v6    

foreach set in country1 country2 country3 { 
   use `set', clear 
   describe, varlist 
   local this `r(varlist)' 
   local exist : list wanted & this 
   keep `exist'
   * save command here 
}

Note that looping over names is absolutely not needed.

Upvotes: 0

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