[Rd] plot(<lm>): new behavior in R-2.2.0 alpha

[John Fox]

Dear Werner,


> -----Original Message-----
> From: Werner Stahel [mailto:stahel at stat.math.ethz.ch] 
> Sent: Friday, September 16, 2005 2:37 AM
> To: Martin Maechler
> Cc: R-devel at stat.math.ethz.ch; John Maindonald; Werner 
> Stahel; John Fox
> Subject: Re: plot(<lm>): new behavior in R-2.2.0 alpha
> 

. . .

> 
> For most plots, I like to see a smoother along with the points.
> I suggest to add the option to include smoothers, not only as 
> an argument to plot.lm, but even as an option().

I agree that smoothers are useful.

. . .

> I clearly support to add either vif or -- equivalent and more 
> intuitive to me -- R^2_j, the coefficient of determination of
> lm(X_j~.) However
> -- this should be included in the coefficient table of print.lm
> -- this adds another useless and misleading quantity for 
> dummy x-variables It is therefore quite a different question.
> 

Generalized variance inflation factors (as computed by the vif function in
car) apply to sets of related regressors in a term, such as dummy
regressors.


. . .

Regards,
 John