On Fri, 27 Nov 2009, Sven Schreiber wrote:
Allin Cottrell schrieb:
> On Fri, 27 Nov 2009, Sven Schreiber wrote:
>
>> ok() also supports lists, while missing() doesn't, is this deliberate?
>
> For ok() with a list argument the return value is unambiguous:
> it's a series with 1s for observations where no values are
> missing, 0s otherwise. With missing() it's not so clear what it
> should return if given a list: 1s for all missing, or for any
> missing?
>
Well, missing() seems to be designed as being in some sense the negation
of ok(). So that would mean missing() is equivalent to "not ok()"; in
this list context missing() would be 1 for *any* missing value in a
variable. Personally this strikes me as quite intuitive and also
practical -- I mean when would you ever be really interested if a series
had *all* n of its values missing, as opposed to, say, "only" n-1 missings?
But I can easily live without it, I was mainly wondering whether this
was just an oversight.
Actually, there could be some scope for allowing list arguments in
missing(): if we had that missing(X) returns 1 when all members of X are
missing, we'd cover all possibilities:
ok(X) = 1 -> none missing
ok(X) = 0 -> some missing (could be all)
missing(X) = 1 -> all missing
missing(X) = 0 -> some ok (could be all)
Riccardo (Jack) Lucchetti
Dipartimento di Economia
Università Politecnica delle Marche
r.lucchetti(a)univpm.it
http://www.econ.univpm.it/lucchetti