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Re: st: Loop year variable


From   emanuele mazzini <madsoenistata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Loop year variable
Date   Mon, 22 Oct 2012 11:44:21 +0200

Ops, sorry about that. You are right, it worked now!

Thank you very much for help!

Kind Regards,

E.M.

2012/10/22 Nick Cox <njcoxstata@gmail.com>:
> You did not do what I suggested.
>
> I suggested
>
> bysort iso_o iso_d (year) :
> by iso_o iso_d :
>
> but your code is
>
> bysort iso_o iso_d year :
> by iso_o iso_d year :
>
> That's quite wrong for your problem. Study the documentation for -by:-
> if you don't see why.
>
> By the way, the code might be slightly better as
>
> bysort iso_o iso_d (year FT_A) :
> by iso_o iso_d :
>
> Nick
>
> On Mon, Oct 22, 2012 at 10:05 AM, emanuele mazzini
> <madsoenistata@gmail.com> wrote:
>> Many thanks Nick. That worked well in the subsample I showed you.
>> However, in my general sample I do not get as many as changes as I
>> thought.
>>
>> I typed the following:
>>
>> bysort iso_o iso_d year: gen date_won = year if FT_A > FT_B | FT_A<FT_B
>> by iso_o iso_d year: replace date_won = date_won[_n-1] if missing(date_w)
>>
>> that seems correct to me, but I only obtain 14 real changes, that are
>> a way too low. That seems actually very strange to me, why I can't get
>> the replace? May it be due to the structure of the dataset? I mean,
>> even though it is not a panel in the proper sense, because I can have
>> more than 1 observation per year, that should not be a matter of
>> concern, because the date_won variable always takes the same value,
>> doesn't it?
>>
>> Many thanks in advance for your help,
>>
>> Regards,
>>
>> Emanuele.
>>
>>
>>
>> 2012/10/22 Nick Cox <njcoxstata@gmail.com>:
>>> See for technique here
>>>
>>> FAQ     . . . . . . . . . . . . . . . . . . . . . . . Replacing missing values
>>>         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
>>>         2/03    How can I replace missing values with previous or
>>>                 following nonmissing values?
>>>                 http://www.stata.com/support/faqs/data/missing.html
>>>
>>> bysort iso_o iso_d (year) : gen datewon = year if !missing(FT_A, FT_B)
>>> & FT_A > FT_B
>>> by iso_o iso_d : replace datewon = datewon[_n-1] if missing(datewon)
>>> gen yrs_won = date - datewon
>>>
>>> Nick
>>>
>>> On Sun, Oct 21, 2012 at 10:37 PM, emanuele mazzini
>>> <madsoenistata@gmail.com> wrote:
>>>> Ok, let's ignore this additional issue for the moment. I can be
>>>> clearer I guess with the following example:
>>>>
>>>>  +---------------------------------------------------------------------+
>>>>      | year   iso_o   iso_d   team_A       team_B   FT_A   FT_B   date_won |
>>>>      |---------------------------------------------------------------------|
>>>>   1. | 1982     ITA     DEU    Italy   Germany FR      3      1       1982 |
>>>>   2. | 1983     ITA     DEU                            .      .          . |
>>>>   3. | 1984     ITA     DEU                            .      .          . |
>>>>   4. | 1985     ITA     DEU                            .      .          . |
>>>>   5. | 1986     ITA     DEU                            .      .          . |
>>>>      |---------------------------------------------------------------------|
>>>>   6. | 1987     ITA     DEU                            .      .          . |
>>>>   7. | 1988     ITA     DEU                            .      .          . |
>>>>   8. | 1989     ITA     DEU                            .      .          . |
>>>>   9. | 1990     ITA     DEU                            .      .          . |
>>>>  10. | 1991     ITA     DEU                            .      .          . |
>>>>      |---------------------------------------------------------------------|
>>>>  11. | 1992     ITA     DEU                            .      .          . |
>>>>  12. | 1993     ITA     DEU                            .      .          . |
>>>>  13. | 1994     ITA     DEU                            .      .          . |
>>>>  14. | 1995     ITA     DEU                            .      .          . |
>>>>      +---------------------------------------------------------------------+
>>>>
>>>> As you can see, the variable date_won is =1982 only for the year in
>>>> which the match was played. Now, I would like to generate a new
>>>> variable that would tell me how many years have gone by since Italy's
>>>> last won (e.g, =0 for 1982, =1 for 1983, =2 for 1984, etc.).
>>>> As I said, I tried with: gen yrs_won=year-date_won but this is the result:
>>>>
>>>>   +---------+
>>>>      | yrs_won |
>>>>      |---------|
>>>>   1. |       0 |
>>>>   2. |       . |
>>>>   3. |       . |
>>>>   4. |       . |
>>>>   5. |       . |
>>>>      |---------|
>>>>   6. |       . |
>>>>   7. |       . |
>>>>   8. |       . |
>>>>   9. |       . |
>>>>  10. |       . |
>>>>      |---------|
>>>>  11. |       . |
>>>>  12. |       . |
>>>>  13. |       . |
>>>>  14. |       . |
>>>>      +---------+
>>>>
>>>> As you can see, such command doesn't produce the expected result. That
>>>> explains why I was looking for a way to expand the value of date_won
>>>> for all cells. I thought that was the reason for the command not to
>>>> work. Do you have any suggestion for overcoming my problem?
>>>>
>>>> Thank you in advance,
>>>>
>>>> Regards,
>>>>
>>>> E.M.
>>>>
>>>>
>>>>
>>>>
>>>> 2012/10/21 Nick Cox <njcoxstata@gmail.com>:
>>>>> I gathered from your original posting that you had yearly data. I
>>>>> understand that matches may be more frequent than yearly, but I can't
>>>>> advise further without seeing what your data look like as the trade
>>>>> data and match data are not obviously compatible.
>>>>>
>>>>> Nick
>>>>>
>>>>> On Sun, Oct 21, 2012 at 1:00 PM, emanuele mazzini
>>>>> <madsoenistata@gmail.com> wrote:
>>>>>> Dear Mr Cox,
>>>>>>
>>>>>> thank you for your reply. The point, however, is that I cannot declare
>>>>>> my dataset to be time-series (how would like but I cannot) due to the
>>>>>> fact that some matches may take place once, twice or even more times
>>>>>> in the same year. That is why I was looking form a manual command. I
>>>>>> may better handle this first? And how can I do that in your opinion?
>>>
>>>
>>> 2012/10/21 Nick Cox <njcoxstata@gmail.com>:
>>>>>>> This should yield to a treatment in terms of spells in the sense of
>>>>>>> -tsspell- (SSC) and of
>>>>>>>
>>>>>>> SJ-7-2  dm0029  . . . . . . . . . . . . . . Speaking Stata: Identifying spells
>>>>>>>         . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
>>>>>>>         Q2/07   SJ 7(2):249--265                                 (no commands)
>>>>>>>         shows how to handle spells with complete control over
>>>>>>>         spell specification
>>>>>>>
>>>>>>> Look at -tsspell- first; it is self-contained. That is, your panels
>>>>>>> are defined by country pairs (dyads) and the start of a spell is
>>>>>>> defined by a match taking place (or a particular result; I don't
>>>>>>> follow exactly what you want, e.g what about draws?). Then a variable
>>>>>>> defined by -tsspell- gives you sequence in spell. You may need to
>>>>>>> subtract 1.
>>>>>>>
>>>>>>> I don't see that loops are needed.
>>>>>>>
>>>>>>> Nick
>>>>>>>
>>>>>>> On Sun, Oct 21, 2012 at 12:07 PM, emanuele mazzini
>>>>>>> <madsoenistata@gmail.com> wrote:
>>>>>>>
>>>>>>>> I am not a new Stata user, but I have to admit I still encounter some
>>>>>>>> problems with writing loops. A loop may not be the solution to the
>>>>>>>> issue I am going to describe, but I thought it is tough.
>>>>>>>>
>>>>>>>> I do have a dataset where I have country-pair trade observations for
>>>>>>>> years 1950-2006 as well as another information, which is football
>>>>>>>> match result for some dyads. I therefore need to generate a variable
>>>>>>>> that indicates how many years are passed since the last won/lost of a
>>>>>>>> country versus another. Suppose FT_A and FT_B are the final results
>>>>>>>> for team A and B. I thought to generate a variable as follows:
>>>>>>>>
>>>>>>>> gen int date_won=year if FT_A>FT_B | FT_A<FT_B
>>>>>>>>
>>>>>>>> in order to get a variable that is = year for every observation I have
>>>>>>>> information about, which reports the year of the won/loss. I then
>>>>>>>> thought to generate another variable (let's say yrs_won) to tell me
>>>>>>>> how many years have gone by as follows:
>>>>>>>>
>>>>>>>> gen int yrs_won=year-date_won
>>>>>>>>
>>>>>>>> Unfortunately, I do not get what I want: the only value yrs_won
>>>>>>>> assumes is 0, but for all years from 1983 until 2006 I would like it
>>>>>>>> to be 1, 2,3 and so on.
>>>>>>>>
>>>>>>>> At the beginning I didn't realize the problem, now it may be occur due
>>>>>>>> to the fact that date_won = year only for the year in which the match
>>>>>>>> was played. I guess I need to do something such as writing a loop to
>>>>>>>> let it spread over all cells of such variable, but I don't really know
>>>>>>>> how to make it. Does anyone of you has any suggestion?
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