[R] Fwd: Potential Issue with lm.influence

[Bert Gunter]

Nothing was attached. The r-help server strips most attachments. Include
your code inline.

Also note that

> 0/0
[1] NaN

so maybe something like that occurs in the course of your calculations. But
that's just a guess, so feel free to disregard.


Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Tue, Apr 2, 2019 at 11:32 AM Eric Bridgeford <ericwb95 using gmail.com> wrote:

> Hi R core team,
>
> I experienced the following issue with the attached data/code snippet,
> where the studentized residual for a single observation appears to be NaN
> given finite predictors/responses, which appears to be driven by the
> glm.influence method in the stats package. I am curious to whether this is
> a consequence of the specific implementation used for computing the
> influence, which it would appear is the driving force for the NaN influence
> for the point, that I was ultimately able to trace back through the
> lm.influence method to this specific line
> <
> https://github.com/SurajGupta/r-source/blob/a28e609e72ed7c47f6ddfbb86c85279a0750f0b7/src/library/stats/R/lm.influence.R#L67
> >
> which
> calls C code which calls iminfl.f
> <
> https://github.com/SurajGupta/r-source/blob/master/src/library/stats/src/lminfl.f
> >
> (I
> don't know fortran so I can't debug further). My understanding is that the
> specific issue would have to do with the leave-one-out variance estimate
> associated with this particular point, which it seems based on my
> understanding should be finite given finite predictors/responses. Let me
> know. Thanks!
>
> Sincerely,
>
> --
> Eric Bridgeford
> ericwb.me
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