[R] Geometric Distribution at prob=c(0,1)

[Kjetil Kjernsmo]

Dear all,

I'm working with the geometric distribution for the time being, and I'm
confused. This may have more to do with statistics than R itself, but
since I'm getting results from R I find counterintuitive (well, yeah, my
statistical intuition has not been properly sharpened), I feel like
asking.

The point first:
If I do
> rgeom(1,prob=1)
I get:
[1] NaN
Warning message: 
NAs produced in: rgeom(n, prob) 
And if I do:
> rgeom(1,prob=0)
I get:
[1] NaN
Warning message: 
NAs produced in: rgeom(n, prob) 

I was expecting to get 0 and Inf respectively.... Should I expect that?

Going back to my textbooks (Dudewicz and Mishra 1988, primarily), they
describe the geometric dist as the dist of a random variable that gives
the number of the trail that an event occurs, with a constant probability
p (or prob). Contrary to R, my textbooks have x = 1, 2, 3, ... 

My intuition says that with this interpretation, a probability of 0 means
that the event just won't happen, and consequently rgeom(1,prob=0) should
always return Inf. qgeom() seems to agree:
> qgeom(1,1)
[1] Inf

rgeom(1,prob=1) says to me that the event must occur on the first trail,
and with x = 0, 1, 2, ..., that means it should return 0. Here, 
> qgeom(0,0)
[1] NaN
Warning message: 
NaNs produced in: qgeom(p, prob, lower.tail, log.p) 

Is it my intuition that is playing tricks with me (again), or is it a bug? 
  
Yours Confusedly,

Kjetil
-- 
Kjetil Kjernsmo
Graduate astronomy-student                    Problems worthy of attack
University of Oslo, Norway            Prove their worth by hitting back
E-mail: kjetikj at astro.uio.no                                - Piet Hein
Homepage <URL:http://www.astro.uio.no/~kjetikj/>
Webmaster at skepsis.no 


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._