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Re: st: RE: How to drop observations
From
natasha agarwal <[email protected]>
To
[email protected]
Subject
Re: st: RE: How to drop observations
Date
Mon, 14 Nov 2011 18:43:05 +0000
Hi Nick,
Thanks for the help. Yes I did. I tried the number of distinct
observations and the sum command as well.
Thanks,
Natasha
On Mon, Nov 14, 2011 at 6:09 PM, Nick Cox <[email protected]> wrote:
> This is two questions not one.
>
> 1. Keeping only firms who switch.
>
> bysort firm (year) : drop if status[1] == status[_N]
>
> Those firms have the same status at the end as the beginning.
>
> bysort firm (status) : drop if status[1] == status[_N]
>
> Those firms never change their status.
>
> Or
>
> bysort firm : keep if status[1] == 0 & status[_N] == 1
>
> for 0 to 1 switches from beginning to end.
>
> See also the FAQ
>
> http://www.stata.com/support/faqs/data/diff.html
>
> which is just a twist away from your problem. Did you search the FAQs before posting?
>
> 2. Keeping only part of a panel. I am not clear about your exact rules, but check out the data management FAQs.
>
> Nick
> [email protected]
>
> natasha agarwal
>
> I want to estimate a model only on those firms where the exporting
> status switches from non-export to export.So for instance.
>
> Firm Year Export Status
> A 2001 0
> A 2002 0
> A 2003 0
> A 2004 1
> A 2005 1
> B 2001 0
> B 2002 0
> B 2003 0
>
> In this I want to drop firm B as it does not change its export status.
> Moreover, for firm A, I want to keep only observation uptil 2004.
>
>
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>
*
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