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Re: st: AW: levelsof problem?


From   Tirthankar Chakravarty <tirthankar.chakravarty@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: AW: levelsof problem?
Date   Tue, 27 Jul 2010 22:50:06 +0530

Nick,

Not sure, but I think this:

levelsof country if eu==1, local(lev) clean
egen eutotal = rowtotal(`lev')

will work only if you set -varabbrev- on. The -unab- tip is a good one
and I thought about it, but the "US_F" variable could be a moving
target (or not).

T

2010/7/27 Nick Cox <n.j.cox@durham.ac.uk>:
> This problem seems to me simpler than is being implied.
>
> The direct problem is that that Joe J needs a varlist to feed to -egen-'s -rowtotal()- function.
>
> His starting point could be the wildcard *_F which catches all the variable names ending in _F. The difficulty is that this includes the US_F variable which for Joe J is a step too far. (At this point I merely hint at the possibility of numerous obvious political jokes without actually making any of them.)
>
> The command -unab-, although usually billed as a programmer's command, is useful here. It does just one thing, unabbreviate (meaning expand) a varlist to all its implied  names, so that
>
> unab all : *_F
>
> unpacks all the names of the variables ending in _F and puts the result in a local macro. To remove US_F from the list we can turn to macro manipulation
>
> local US US_F
> local eu : list all - US
>
> which gives us a macro -eu- containing the desired names.
>
> Some people might want to emphasise that the varlist expansion is also done by other commands: see e.g. help on -describe, varlist-, -ds-, or -findname- (SJ). But any of those does much more than this one thing, so it is most straightforward to stick to -unab-.
>
> It also happens that the names of the countries concerned are held as values of Joe J's string variable -country-. The only real problem here is that the list result returned by -levelsof- is complicated by double quote delimiters, but as Tirthankar shows -- and the help file clearly explains -- an option -clean- gets rid of those.
>
> For Joe J's example dataset
>
> levelsof country if eu==1, local(lev) clean
> egen eutotal = rowtotal(`lev')
>
> should have worked so far as I can see. There is no need, for the example dataset, to spell out the _F suffix, although Tirthankar's code shows how to do it if needed.
>
> Confusion on names: Joe J mixed references to
>
> 1. -egen, rsum()- and -egen, rowtotal()-.
> 2. -levels- and -levelsof-.
>
> In both cases (just a coincidence, this) the second name has been the preferred name since Stata 9.
>
> Nick
> n.j.cox@durham.ac.uk
>
> joe j
>
> Thanks a lot, Tirthankar!
>
> Tirthankar Chakravarty
>
>> Then this (cumbersome) script should do what you want:
>> *********************************************
>> clear
>> input str2 country      eu      GE_F NL_F  UK_F US_F
>> US      0       1       1       1       0
>> US      0       1       1       1       0
>> NL      1       1       0       1       1
>> IN      0       1       1       1       1
>> GE      1       0       1       1       1
>> GE      1       0       1       1       1
>> US      0       1       1       1       0
>> US      0       1       1       1       0
>> US      0       1       1       1       0
>> PT      1       1       1       1       1
>> end
>> g PT_F = 2
>> levelsof country if eu==1, local(lev) clean
>> local lev2
>> foreach x of local lev {
>>        local lev2 " `lev2' `x'_F "
>> }
>> egen eutotal = rowtotal(`lev2')
>> *********************************************
>
> joe j
>
>>> Thanks, Martin. This is not quite what I wanted; The following command
>>>  is good enough.
>>> egen eutotal=rowtotal(GE_F NL_F  UK_F)
>>>
>>> The *_F variables need to be selected based on whether they belong to
>>> eu or not (GE_F NL_F  UK_F are selected, but not US_F) (The values of
>>> _*F variables are not based on whether eu=1 or otherwise).  But there
>>> are many groupings, like eu, and a lot of countries, so I was looking
>>> for an easy method to select. But it seems to me that manual selection
>>> is the only choice.
>
> Martin Weiss
>
>>>> You could of course -replace- to the values you want based on the -if-
>>>> qualifier after the fact:
>>>>
>>>>
>>>> *************
>>>> egen eutotal=rowtotal(GE_F NL_F  UK_F)
>>>> replace eutotal=. if !eu
>>>> *************
>>>>
>>>>
>>>> The reason that your second approach does not work is that Stata expects a
>>>> -varlist- while you feed it
>>>>
>>>> `"GE"' `"NL"' `"PT"'_F
>>>>
>>>> which it cannot process. Type -ma di- to see the contents of your -macro-s.
>
> joe j
>
>>>> >From a data set roughly like the following
>>>> clear
>>>> input str2 country      eu      GE_F NL_F  UK_F US_F
>>>> US      0       1       1       1       0
>>>> US      0       1       1       1       0
>>>> NL      1       1       0       1       1
>>>> IN      0       1       1       1       1
>>>> GE      1       0       1       1       1
>>>> GE      1       0       1       1       1
>>>> US      0       1       1       1       0
>>>> US      0       1       1       1       0
>>>> US      0       1       1       1       0
>>>> PT      1       1       1       1       1
>>>> end
>>>>
>>>> I want to calculate the  row sum of all *_F variables pertaining to eu
>>>> countries (all excluding US_F):
>>>> egen eutotal=rowtotal(GE_F NL_F  UK_F)
>>>>
>>>> However, I would prefer to follow some rules in selecting the variables,
>>>> like
>>>>
>>>> levels country if eu==1, local(lev)
>>>> egen eutotal=rsum(`lev'_F)
>>>>
>>>> This doesn't work, however. Any pointers would be appreciated.
>
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