Re: st: RE: Merge problem

[Alfonso Sanchez-Penalver <oneiros_spain@yahoo.com>]

Hi again Erik,

It was my understanding that you didn't have the periods in dataset (A) and you were trying to generate just that. And that you wanted to have the period identifier to increase as years increase. My understanding from the previous posts is that dataset (A) is going to be data where each observation is identified by a unique pair of year and firm_id, i.e. The firm_id may be repeated for several years, but the combination of the firm_id with a given year is unique and not repeated. If my understanding is correct and you want to generate a period_id that starts at 1 for the first firm and the first year, and then continues to increase when you get to the second firm and the first year in dataset (A) then what I told you will do exactly that. If you want the same period ids in different firms then I must have missed something in your previous messages and I apologize. 

Alfonso Sánchez-Peñalver

> On Oct 4, 2013, at 9:48 AM, Erik Aadland <erikaadland@hotmail.com> wrote:
> 
> Thanks for your suggestion Alfonso.
> 
> All observations in a given period should have the same period_id.
> Following my example dataset, all expanded observations in dataset (A) in period 1 in year 1 should have period_id == 1.
> All observations in period 2 in year 1 should have period_id == 2.
> All observations in period 1 in year 2 should have period_id == 3
> All observations in period 2 in year 2 should have period_id == 4
> 
> Regards,
> Erik.
> 
> 
> 
> ----------------------------------------
>> Subject: Re: st: RE: Merge problem
>> From: oneiros_spain@yahoo.com
>> Date: Fri, 4 Oct 2013 09:31:21 -0400
>> To: statalist@hsphsun2.harvard.edu
>> 
>> Do you mean that the period then is just an increasing id? Because if so after you have expanded by year, sort by firmid and year, and simply generate the period with _n with no bysort.
>> 
>> Alfonso Sánchez-Peñalver
>> 
>>> On Oct 4, 2013, at 9:26 AM, Erik Aadland <erikaadland@hotmail.com> wrote:
>>> 
>>> 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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