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Re: st: Duplicate observations
From
emanuele mazzini <[email protected]>
To
[email protected]
Subject
Re: st: Duplicate observations
Date
Tue, 11 Mar 2014 00:08:40 +0100
Thank you!!
2014-03-10 19:35 GMT+01:00 Nick Cox <[email protected]>:
> Duplicates are a red red herring herring here.
>
> (http://en.wikipedia.org/wiki/Red_herring may help internationally.)
>
> To keep the last only
>
> bysort reporter partner (date) : keep if _n == _N
>
>
>
>
> Nick
> [email protected]
>
>
> On 10 March 2014 18:30, emanuele mazzini <[email protected]> wrote:
>> Hello to everybody,
>>
>> I have an issue about duplicate observations that I find puzzling to solve.
>> I have data on country-pairs by year and I am interested in two
>> specific variables, a date and, say a variable which I call x_1.
>>
>> Specifically, my data look like this :
>>
>> reporter partner year date x_1
>>
>> Albania Austria 1980 6dec1980 n_1
>> Albania Austria 1980 15nov1980 n_1
>> . . .
>> . . .
>> . . .
>>
>> As you may have noticed observations differ amongst them only by date
>> and I need to drop them so as to keep the most recent one (hence, in
>> this case the second one).
>>
>> I ran the following commands:
>>
>> duplicates tag reporter partner year, generate(dup)
>>
>> by reporter partner year (x_1 -date), sort: gen duplicates=_n
>>
>> so as to be able to identify duplicates and then - among those with
>> dup >0 - drop those for which duplicates > 1.
>> This method was suggested in this thread (I take this opportunity to
>> thank again), but it seems not to work for some observations.
>> Take, for instance the following example:
>>
>> reporter partner year date x_1 dup duplicates
>> Albania Germany 1967 08apr1967 n_1 1 1
>> Albania Germany 1967 17dec1967 n_1 1 2
>>
>> As you may notice, Stata identifies the observation occurred the
>> 17dec1967 as those with duplicates > 1 (which will then be dropped),
>> while I would have expected Stata to make the opposite.
>>
>> Can anyone explain me why and, possibly, tell me how to deal with such issue?
>>
>> Thank you very much in advance,
>>
>> Emanuele
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/faqs/resources/statalist-faq/
>> * http://www.ats.ucla.edu/stat/stata/
> *
> * For searches and help try:
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> * http://www.ats.ucla.edu/stat/stata/
*
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