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Re: st: Different results with the same code
From
Nick Cox <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: Different results with the same code
Date
Mon, 10 Feb 2014 10:08:00 +0000
Wrong way round: -collapse- reports (firstnm) as it finds them; it's
the sorting that includes some arbitrariness.
But evidently you have different values on variables for which you
select (firstnm), so why do you want to pick the first non-missing and
what sort order do you want?
Nick
[email protected]
On 10 February 2014 09:59, Estrella Gomez <[email protected]> wrote:
> Hi, Nick
>
> I have tried sorting just before the collapse and it happens the same
> thing. Does (firstnm) use random values each time then?
>
> Thank you,
> Estrella
>
> 2014-02-10 10:41 GMT+01:00 Nick Cox <[email protected]>:
>> Contrary to your claim, I would point at this:
>>
>> Which values are (firstnm) is likely to depend on the exact sort order
>> of your data and you are sorting before you -collapse-.
>>
>> As Phil Schumm often explains, you could get consistent results by
>> insisting on stable sorting, but that would be hiding a bug. There's
>> evidently some arbitrariness that is better fixed directly.
>> Nick
>> [email protected]
>>
>>
>> On 10 February 2014 09:07, Estrella Gomez <[email protected]> wrote:
>>> Dear Statalisters
>>>
>>> I am running a code and I have realized that every time I run it the
>>> results (the coefficients and the standard errors) are different. This
>>> is the code:
>>>
>>> clear all
>>> use "itunes_grav_song", clear
>>> sort id country orig
>>>
>>> egen nb_id=tag(id)
>>> bysort orig: egen nr_orig=sum(nb_id)
>>> bysort orig country: egen nr_dest=sum(available)
>>> gen avail_share=(nr_dest/nr_orig)
>>> collapse (count) nr_songs=id (firstnm) contig comlang ldist
>>> avail_share, by(country orig)
>>> encode country, gen(d_id)
>>> encode orig, gen(o_id)
>>> gen home=country==orig
>>>
>>> reg avail_share ldist comlang home i.d_id i.o_id
>>>
>>>
>>> I have checked and after the collapse I obtain every time the same
>>> dataset, so I don't know what can be the reason
>>>
>>> Thanks for any help!
>>> Estrella
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