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Re: st: Find the fiscal year for each obs


From   Tom <tommedema@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Find the fiscal year for each obs
Date   Sat, 6 Apr 2013 16:45:25 +0200

Dear Yu Chen,

It might be that the discussion at
http://www.nber.org/sys-admin/large-stata-datasets.html is helpful to
you. It specifically addresses large datasets.

Kind regards,
Tom

On Sat, Apr 6, 2013 at 4:24 PM, Yu Chen, PhD <profyuchen@gmail.com> wrote:
> Nick,
> Thank you so much for the code. It works great. However, I have a
> further question. Assume File A has 5000 firms, and each has 360 daily
> stock price observations for 5 years, then there are 9,000,000
> observations in File A. Assume File B has 5 years data (i.e., fiscal
> year definition) for each firm, then there are 25,000 observations in
> File B. If I use -merge-, the resulting file will be too large for the
> computer to handle. So I think some kind of loop structure might need
> to be used. Or there may be a better solution. Could you please help
> me in this regard? What code will be good to handle this problem?
> Best,
>
> Yu Chen
>
>
>
>
> On Sat, Apr 6, 2013 at 6:50 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>> I'd just -merge- the files. The convention seems to be that Fiscal
>> Years are labelled by the year they start in. (It's _always_ a good
>> idea to explain stuff that won't be universally understood; assuming
>> that people work in your field is usually wrong.) Either way, there's
>> a correction for dates that are in calendar years that differ from
>> fiscal years. This example uses slightly different fake data. I used
>> an ancient -merge- only because I am writing from an ancient machine.
>> (I have Stata 12, but this machine doesn't read DVDs.)
>>
>> clear
>> input str3 Firm str10 Date
>> IBM    "2009/01/15"
>> IBM    "2010/01/16"
>> 3M     "2010/07/01"
>> 3M     "2011/07/02"
>> end
>> gen Ndate = date(Date, "YMD")
>> gen Fiscal = year(Ndate)
>> sort Firm Fiscal
>> save FileA, replace
>>
>> clear
>> input str3 Firm  Fiscal  str10 Begin str10 End
>> IBM    2009               "2009/03/01"   "2010/02/28"
>> IBM    2010               "2010/03/01"   "2011/02/28"
>> 3M    2010               "2010/06/01"    "2011/05/31"
>> 3M     2011               "2011/06/01"     "2012/05/31"
>> end
>>
>> gen Nbegin = date(Begin, "YMD")
>> gen Nend = date(End, "YMD")
>> sort Firm Fiscal
>>
>> version 10: merge Firm Fiscal using FileA
>>
>> replace Fiscal = Fiscal - 1 if !inrange(Ndate, Nbegin, Nend)
>> drop _merge
>> list Firm Fiscal Begin End Date
>>
>>
>> Nick
>> njcoxstata@gmail.com
>>
>>
>> On 6 April 2013 12:15, Yu Chen, PhD <profyuchen@gmail.com> wrote:
>>
>>> I have two files. File A contains the daily stock price for each firm,
>>> and file B contains the beginning and ending dates for a fiscal year
>>> for each firm. See below for an illustration (data are hypothetical):
>>>
>>> File A:
>>> Firm   Date                Price
>>> IBM    2009/01/15       xxxx
>>> IBM    2009/01/16       xxxx
>>> ...................
>>> 3M     2010/07/01       yyyy
>>> 3M     2010/07/02       yyyy
>>> ...................
>>>
>>> File B:
>>> Firm   Fiscal Year      Beg. Date    End. Date
>>> IBM    2009               2009/03/01   2010/02/28
>>> IBM    2010               2010/03/01   2011/02/28
>>> ..................
>>> 3M     2010               2010/06/01    2011/05/31
>>> 3M     2011               2011/06/01     2012/05/31
>>> ..................
>>>
>>> Now, I want indicate in File A for each observation the fiscal year
>>> the observation belongs to, according to the definition in File B.
>>> Conceptually it seems easy: Just compare the date of the observation
>>> in File A with the beginning and ending dates in File B.
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