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Re: st: Capturing unique actors meeting conditions by focal actor and year (excluding focal actor)


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Capturing unique actors meeting conditions by focal actor and year (excluding focal actor)
Date   Tue, 16 Oct 2012 11:49:22 +0100

I suspect that you didn't copy all the code. The  last line of code
has a brace (curly bracket }) by itself.

On Tue, Oct 16, 2012 at 11:44 AM, Erik Aadland <erikaadland@hotmail.com> wrote:
> Thank you Nick!
> You are quite right. I was imprecise; it is distinct actors I want to capture.
> When I run your suggested code, I get this error message after the following line of code:
>
> qui forval a = 1/`nact' {
> unexpected end of file
> r(612);
>
> What could possibly cause this error message? I am using Stata 10.
> Thanks again and kind regards,
> Erik.
>
>
> ----------------------------------------
>> Date: Tue, 16 Oct 2012 11:19:41 +0100
>> Subject: Re: st: Capturing unique actors meeting conditions by focal actor and year (excluding focal actor)
>> From: njcoxstata@gmail.com
>> To: statalist@hsphsun2.harvard.edu
>>
>> First off, on my list of hobby-horses is a prejudice that the word
>> "unique" is misused here, although you are in very good company:
>> StataCorp itself does it in various places, e.g. -codebook-, although
>> I am working on changing their habits if I can. The word "unique"
>> strictly means occurring once only; I recommend the word "distinct"
>> for what you want. There is a longer discussion of terminology in
>>
>> SJ-8-4 dm0042 . . . . . . . . . . . . Speaking Stata: Distinct observations
>> (help distinct if installed) . . . . . . N. J. Cox and G. M. Longton
>> Q4/08 SJ 8(4):557--568
>> shows how to answer questions about distinct observations
>> from first principles; provides a convenience command
>>
>> That said, when faced with a problem like yours, vague ideas of
>> possible solutions rise up. Is this a case for associative arrays as
>> implemented in Mata? Is there a cunning restructuring of the data from
>> which the answer would fall out easily? Precise inspiration was
>> lacking and what seemed crucial was that you need to consider each
>> actor in each combination of project and year. That pointed out to
>> loops over actors _and_ over project-years. Once that idea was taken
>> up, life is usually easier if all identifiers run over the integers
>> from 1 up. Also, the flavour of compiling a list and eventually
>> counting distinct members of other actors suggested -levelsof- and the
>> list manipulation tools documented at -help macrolists-.
>>
>> So, here is my code. Absolutely nothing rules out other kinds of solutions.
>>
>> input year project_id actor_id condition wanted
>> 2000 1 1 1 2
>> 2000 1 2 0 1
>> 2000 1 3 0 1
>> 2000 1 7 1 2
>> 2000 2 1 1 2
>> 2000 2 2 0 1
>> 2000 2 3 0 1
>> 2000 3 4 1 2
>> 2000 3 5 0 1
>> 2000 3 6 0 1
>> 2000 3 . . .
>> 2001 4 1 1 2
>> 2001 4 2 0 1
>> 2001 4 3 0 1
>> end
>>
>> * identifiers guaranteed to run 1 up if the real ones don't!
>> * note that "same project, same year" defines a group
>> egen proj = group(project_id year), label
>> su proj, meanonly
>> local nproj = r(max)
>>
>> egen act = group(actor_id), label
>> su act, meanonly
>> local nact = r(max)
>>
>> gen mywanted = .
>>
>> * lists of those in each project and year and condition == 0
>> qui forval p = 1/`nproj' {
>> levelsof act if proj == `p' & condition == 0, local(who`p')
>> }
>>
>> macro list
>>
>> * now cycle over actors
>> qui forval a = 1/`nact' {
>>
>> * blank out workspace
>> local work
>>
>> * if actor was included, we want to add that list to workspace
>> * in practice -if r(N)- will be true if and only if -r(N)- is positive
>> forval p = 1/`nproj' {
>> count if act == `a' & proj == `p'
>> if r(N) local work `work' `who`p''
>> }
>>
>> * remove duplicates
>> local work : list uniq work
>> * remove this actor
>> local work : list work - a
>> * see what we got for debugging
>> noi di "`a' `work'"
>>
>> replace mywanted = `: list sizeof work' if act == `a'
>> }
>>
>> Nick
>>
>>
>> On Tue, Oct 16, 2012 at 9:52 AM, Erik Aadland <erikaadland@hotmail.com> wrote:
>>
>> > I am trying to generate a variable "wanted" that by each focal actor and year captures the total number of unique actors (excluding the focal actor) that meet a specified condition (condition == 0) and that the focal actor has occured together with in one or more projects.
>> > This is my data structure:
>> > year project_id actor_id condition wanted
>> > 2000 1 1 1 2
>> > 2000 1 2 0 1
>> > 2000 1 3 0 1
>> > 2000 1 7 1 2
>> > 2000 2 1 1 2
>> > 2000 2 2 0 1
>> > 2000 2 3 0 1
>> > 2000 3 4 1 2
>> > 2000 3 5 0 1
>> > 2000 3 6 0 1
>> > 2000 3 . . .
>> > 2001 4 1 1 2
>> > 2001 4 2 0 1
>> > 2001 4 3 0 1
>> > .....and so on
>> > So in year == 2000, actor_id == 1 has occurred with 2 unique actor_id (namely 2 and 3) meeting condition == 0 in projects. Therefore, wanted == 2 for actor_id == 1 in year == 2000.
>> > My attempted code (which is quite wrong):
>> > sort actor_id year projects ;
>> > by actor_id year: gen nvals = _n == 1 ;
>> > sort actor_id year project_id ;
>> > egen wanted = total(nvals & condition == 0), by(agency_id year) ;
>> > replace wanted = wanted - (nvals & condition == 0) ;
>>
>> *
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>> * http://www.ats.ucla.edu/stat/stata/
> *
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