Olena Stavrunova
> > I have a panel data (id and quarters). Could you, please,
> let me know how to
> > delete the entire case, that is all observations for the
> individual if, for
> > example, in at least one quarter variable v1 takes a
> negative value for this
> > individual.
> >
John Hennen
> Try-
> tempvar x y
> gen `x' = v1<0
> egen `y' = max(`x'),by(id)
> drop id if `y' ==1
There is a typo here. John meant
. drop if `y' == 1
You can use expressions as arguments
to many -egen- functions.
So another way to do it might be
. egen nneg = sum(v1 < 0), by(id)
. drop if nneg
Within using any new variables,
you could also
. bysort id (v1) : drop if v1[1] < 0
This is very Stataish. You
sort on -id-
. sort id
and within that you sort on -v1-,
so it is as if you said
. sort id v1
except that you want to do things
. by id:
You can combine the syntaxes:
. bysort id (v1):
After this -sort- if any value
for each -id- is negative, then
the minimum will also be negative,
and that will be first within each
-id-. Hence we can -drop- each -id- if the
first value is negative.
. bysort id (v1) : drop if v1[1] < 0
If the condition was that _all_ values
were negative that would be
. bysort id (v1) : drop if v1[_N] < 0
except that missing values complicate
this. You are better off using some -max()-
function.
Nick
[email protected]
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