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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   Sun, 21 Oct 2012 23:37:37 +0200

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?
>>
>> Thanks in advance,
>>
>> E.M.
>>
>> 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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