I haven't tried understanding Sergio's code, as it
appears to take no account of the fact that this is panel data
and so calculations must be done separately for each
identifier.
Consider starting with -id-, -eventid- and -outcome-. Then
bysort id (eventid) : gen order = sum(outcome == 2) * (outcome == 2)
or
bysort id (eventid) : gen order = cond(outcome == 2, sum(outcome == 2), 0)
-outcome == 2- evaluates as 1 or 0 depending on whether it is true
or false, and the -sum()- gives you the cumulative sum.
Furthermore each occurrence of -outcome == 2- defines a new
"spell":
by id : gen spell = sum(outcome == 2)
bysort id spell (eventid) : gen four = sum(outcome == 4)
by id spell : replace four = four[_N]
by id : gen indicator = four[_n - 1] > 0 if outcome == 2
The "spell" point of view is simple but gives you a handle
on many problems in this territory. It is really piggy-backing
on -by:-. For spell incantations, see -tsspell- on SSC and
its quite detailed help file. For -by:- explanations, -search
by- and follow up manual and Stata Journal references.
As Sergio says, -egen- is another route here but a path from#
first principles is always instructive.
Nick
[email protected]
Sergio Correia
> This works but I'm pretty sure its not the best way:
>
> * CODE:
> gen xyz = outcome==4
> replace xyz = (xyz[_n-1]==1 | xyz ==1) & (outcome!=2)
> gen indicator = xyz[_n-1]==1 if order>1
>
>
> Line 1 is straightforward.
> Line 2 is 1 if there has been an outcome of 4 since the last success
> (and we are not on a successful outcome)
> Line 3 is also simple
>
> The last two lines can be merged but that would make them harder to
> understand. Again, I'm sure there are better answers (maybe egen, sum
> or more complex gens).
Le Wang
> > I have a data set containing four variables
> >
> > (1) household id (2) event id (3) event outcome (4) order of success
> >
> > event outcomes can takes on values of 1,2,3,4; if the event
> outcome is
> > 2, it is successful and ordered according to the timing of occurance
> > of the success (recorded in the fourth variable "order of success").
> > The data looks like what follows,
> >
> >
> --------------------------------------------------------------
> ---------------------------
> > id eventid outcome order of success
> > 1 1 1 0
> > 1 2 2 1
> > 1 3 4 0
> > 1 4 2 2
> > 2 1 2 1
> > 2 2 4 0
> > 2 3 4 0
> > 2 4 3 0
> > 2 5 2 2
> > 3 1 2 1
> > 3 2 2 2
> > 3 3 1 0
> > 3 4 4 0
> > 3 5 2 3
> > .
> > .
> > .
> > .
> >
> --------------------------------------------------------------
> ---------------------------
> >
> > What I wanna do is to create a variable for obs with the order of
> > success greater than 1; this variable indicates whether or not there
> > exists an event outcome equal to 4 during the interval between this
> > success and the previous success. The final data for the example
> > should look like the following
> >
> >
> --------------------------------------------------------------
> ---------------------------
> >
> > id eventid outcome order of success indicator
> > 1 1 1 0 .
> > 1 2 2 1 .
> > 1 3 4 0 .
> > 1 4 2 2 1
> > 2 1 2 1 .
> > 2 2 4 0 .
> > 2 3 4 0 .
> > 2 4 3 0 .
> > 2 5 2 2 1
> > 3 1 2 1 .
> > 3 2 2 2 0
> > 3 3 1 0 .
> > 3 4 4 0 .
> > 3 5 2 3 1
> > .
> > .
> > .
> > .
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