[Rd] standardized residuals (rstandard & plot.lm) (PR#8468)

[Prof Brian Ripley]

Martin,

I tend to think that points with hii = 1 are best omitted, as in almost 
all cases you already know about them.  I've yet to hear of a better 
compromise.

Incidentally, this is neither a case of the subject nor of 8367 which that 
subject line refers to.  So 8367 was fixed.

Brian


On Tue, 10 Jan 2006 maechler at stat.math.ethz.ch wrote:

>>>>>> "Heather" == Heather Turner <Heather.Turner at warwick.ac.uk>
>>>>>>     on Tue, 10 Jan 2006 14:30:23 +0100 (CET) writes:
>
>    Heather> This bug is not quite fixed - the example from my
>    Heather> original report now = works using R-2.2.1, but
>
>    Heather> plot(Uniform, 6)
>
>    Heather> does not. The bug is due
>
>    .........
>     g <- hatval/(1 - hatval) # Potential division by zero here
>
>     plot(g, cook, xlim = c(0, max(g)), ylim = c(0, ymx),
>     ..........
>
>    Heather> All other values of 'which' seem to work
>    Heather> fine. Sorry not to have checked this in the beta
>    Heather> version,
>
> (indeed; that would have been useful)
>
>
> Hmm, it's not clear what *should* be drawn in such a
> case. Leaving away all the observations with  h_ii = 1
> seems a particularly bad idea, since these are the ones that
> you'd definitely should remark.
> OTOH, for h_ii = 1, the cook distance is 'NaN'
> (or should that be changed; to  "very large" instead ???)
> and plot number 6 doesn't seem to make any sense to me
>
> When 'which = 6' was proposed
> [ on R-devel as well, last April,
>  http://tolstoy.newcastle.edu.au/R/devel/05/04/0595.html
>  ah, I see, by David Firth, from your place, so, Heather, can you
>  make sure he sees this e-mail ?
> ]
> I actually had wondered a bit about it's general usefulness,..
>
> ---
>
> But the example is useful anyway; I think that also plot
> number 5, (R_i vs h_ii) does the wrong thing currently by just
> leaving away all points for which h_ii = 1.
> These really should be shown one or the other way!
>
> Martin
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
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