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RE: st: RE: Merge problem


From   Erik Aadland <erikaadland@hotmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   RE: st: RE: Merge problem
Date   Fri, 4 Oct 2013 13:26:08 +0000

Following up on Joe's code, I did the following:

expand 2 if year == 2003 ;
expand 2 if year == 2004 ;

bys year agency_id: gen period_id=_n  ;

In this code, I can specify the correct number of periods for each year.

However, the code starts counting periods in each year starting from 1.
I would like to have the code continue the counting from the highest number in the previous year.
In the simple example above, the periods should be 3 and 4 for year == 2004 above, not 1 and 2.

Is there a way to accomplish this?

Thanks,

Erik.



----------------------------------------
> From: erikaadland@hotmail.com
> To: statalist@hsphsun2.harvard.edu
> Subject: RE: st: RE: Merge problem
> Date: Fri, 4 Oct 2013 12:10:32 +0000
>
> Dear Joe.
>
> Thank you for your suggestion.
>
> The number of periods is not completely fixed in dataset (B).
> In year == 1, I have periods (1-8)
> In year == 2, I have periods (9-17)
> In year == 3, I have periods (18-28)
> In year == 4, I have periods (29-39)
> In year == 5, I have periods (40-50)
> In year == 6, I have periods (51-61)
> In year == 7, I have periods (62-72)
> In year == 8, I have periods (73-75)
>
> So a total of 75 periods spread over 8 years in dataset (B).
>
> Sincerely,
> Erik.
>
>
>> From: jcanner1@jhmi.edu
>> To: statalist@hsphsun2.harvard.edu
>> Subject: st: RE: Merge problem
>> Date: Fri, 4 Oct 2013 11:56:06 +0000
>>
>> Erik,
>>
>> If there are a fixed, known number of periods per year, you can use -expand- in dataset (A). Suppose (as in your example) there are 4 periods (1,2,3,4):
>>
>> . expand 3
>> . bys year firm_id: gen period_id=_n
>>
>> However, if the number of periods depends on some information in dataset (B), that's a different story. If so, please provide more information on how the number of periods is to be determined.
>>
>> Regards,
>> Joe Canner
>> Johns Hopkins University School of Medicine
>>
>> ________________________________________
>> From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Erik Aadland [erikaadland@hotmail.com]
>> Sent: Friday, October 04, 2013 4:18 AM
>> To: statalist@hsphsun2.harvard.edu
>> Subject: st: Merge problem
>>
>> Dear Statalist.
>>
>> I have two datasets. One dataset (A) contains the variables "year" and "firm_id". A firm observation ("firm_id") occurs only once in a given "year".
>>
>> The other dataset (B) contains the variables "year", "period_id" and "firm_id". There are many periods within a given year, and firm observations ("firm_id") are nested within periods. So a given firm ("firm_id") may occur several times in a given year. The firms in (A) are not the same firms as in (B). The structure of (A) and (B) are as follows.
>>
>> (A):
>> year firm_id
>> 2003 1
>> 2003 2
>> 2003 3
>> 2003 4
>> 2004 1
>> 2004 2
>> 2004 5
>> 2004 6
>>
>> (B):
>> year period_id firm_id
>> 2003 1 11
>> 2003 1 12
>> 2003 2 13
>> 2003 2 14
>> 2003 2 11
>> 2004 3 11
>> 2004 3 12
>> 2004 3 15
>> 2004 4 16
>> 2004 4 17
>>
>> I want to merge the firms in (A) into (B) such that the firms in (A) in a given year occur in all periods for the corresponding year in (B). The problem is that I don't have "period_id" for my firm observations in (A).
>>
>> Is there a smart way to handle this problem? I use Stata 12.
>>
>> Any input on this would be much appreciated.
>>
>> Sincerely,
>> Erik
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