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Re: st: Observations that keep a feature in the whole sample period


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Observations that keep a feature in the whole sample period
Date   Tue, 21 May 2013 23:26:09 +0100

Correct on -keep-. Sorry about that.

The -sort- order

bysort entity (const_a) :

ensures that -const_a[1]- is the lowest for each agent, not the first.
If the lowest value for each agent is above the threshold, then all
the observations for that agent  are above.
Nick
njcoxstata@gmail.com


On 21 May 2013 23:16, Miguel Angel Duran Munoz <maduran@uma.es> wrote:
> Thanks, Nick. I guess you mean -keep- instead of -drop-. Nevertheless, the
> command that you suggest would not guarantee that I keep the agents that
> have been above the threhsold for the whole sample period (ie, I would be
> including agents that were above the threshold in the first period and
> then might have been above or below it).
>
>> Sounds like
>>
>> bysort entity (const_a) : drop if const_a[1] > 0.09716
>>
>> Nick
>> njcoxstata@gmail.com
>>
>> On 21 May 2013 23:01, Miguel Angel Duran Munoz <maduran@uma.es> wrote:
>>> Hi, Statalisters. I want to focus on agents in my dataset that have a
>>> particular feature; specifically, for those agents, and for each and
>>> every
>>> period (out of 64), the value of a variable (const_a) is larger than a
>>> particular threshold (0.097116). I have done what I show below.
>>> Nevertheless, I have realized that some of my agents are not in the
>>> sample
>>> since the first period, so what I am doing would mistakenly eliminate
>>> them. Will anyone help to solve this problem? Thanks in advance.
>>>
>>> bysort entity (date2): gen obs=_n
>>> drop if const_a<0.097116
>>> by entity: drop if obs[_N]<64
>>>
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