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Re: st: How to drop missing values by period?


From   Xixi Lin <winnielxx@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to drop missing values by period?
Date   Mon, 11 Feb 2013 10:18:00 -0500

Hi Nick,

Thanks for the instant reply. What I mean is like:
id	period	x1	x2
1	1	1	4
2	1	2	.
3	1	.	2
1	2	4	4
2	2	5	3
3	2	.	2

In period 1, I want to keep id 1 because id 2 and id 3 have missing
values; in period 2, I want to keep id 1 &2, because id 3 has missing
values.

I have time series data, but I wanna do a cross-sectional regressions
and wanna keep the maximum of observations. So I am wondering if it is
possible to drop obs only in one period while keeping it in  another
period.

Thanks.
Xixi Lin

On Mon, Feb 11, 2013 at 9:59 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> This sounds to me as if you want -keep- and -drop- the same
> observations. That can't be done.
>
> Perhaps you should show what your data look like with variable names,
> and link your question to such an example.
>
> Nick
>
> On Mon, Feb 11, 2013 at 2:53 PM, Xixi Lin <winnielxx@gmail.com> wrote:
>
>> I tried to drop missing values period by period, in 120 periods. In other
>> words, in period 1, I want to drop the observations if dependent variables
>> have missing values only in period 1; while in period 2, drop the
>> observations if dependent variables have missing values only in period 2,
>> should keep those that missing in period 1 but not missing in period 2. For
>> instance:
>>
>> In period 1, I want to keep id 1; in period 2, I want to keep id 1 &2.
>>
>> Does anyone knows how to do that? Thanks a lot.
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