Gao Liu's strategy has also been written up in
SJ-7-3 pr0033 . . . . . . . . . . . . . . Stata tip 51: Events in
intervals
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N.
J. Cox
Q3/07 SJ 7(3):440--443 (no
commands)
tip for counting or summarizing irregularly spaced
events in intervals
-- but it does require a previous command such as
generate alliance_no = .
There can be no -replace- unless the variable already exists.
Related material is included in
SJ-7-4 dm0033 . . . . . . Speaking Stata: Counting groups, especially
panels
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N.
J. Cox
Q4/07 SJ 7(4):571--581 (no
commands)
discusses how to count panels through reduction commands
or through tabulation commands and how to overcome
problems that do not yield easily to these approaches
SJ-7-1 pr0029 . . . . . . . . . . . . . . . Speaking Stata: Making it
count
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N.
J. Cox
Q1/07 SJ 7(1):117--130 (no
commands)
discusses count used with a loop over observations
or variables
By the way, it helps everyone if you choose informative titles (not, in
this case, "Question").
Nick
[email protected]
Gao Liu
=======
Here is one way:
sort firm_name alliance_date
qui forval i = 1/`=_N' {
count if firm_name == firm_name [`i'] &
inrange(alliance_date-alliance_date[`i'] , 1, (5*365+1))
replace alliance_no= r(N) in `i'
}
It may take a while, as it has to run through all observations one by
one, but it should work.
Thomas Zhu or Zhu Yi
====================
> I am working on a project that examines a firm's international
strategic alliance (ISA).
>
> In my huge dataset, I have around 2000 firms forming ISA between
01/01/1989- 0/01/1999. Each firm is likely to form multiple
international strategic alliances during this period.
> For example: Firm A forms the first strategic alliance on 01/02/1989;
the second on 04/09/1990; the third on 06/09/1997.
>
> What I need to record is the number of new strategic alliances that
the firm forms within 5 years after the focal one.
> For firm A, the number of new strategic alliances that Firm A forms
within 5 years is 1 corresponding to its first strategic alliance on
01/02/1989;
> the number of new strategic alliances that Firm A
forms within 5 years is 0 corresponding to its second strategic
alliance on 04/09/1990 ;
> the number of new strategic alliances that Firm A forms
within 5 years is 0 corresponding to its third strategic alliance on
06/09/1997;
>
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