[R] passing an extra argument to an S3 generic

[ilai]

You do not provide mlm.influence() so your code can't be reproduced.

Or did you mean to put lm.influence() in the formals to your hatvalues.mlm ?

If yes, then 1) you have a typo 2) lm.influence doesn't allow you to
pass on arguments, maybe try influence.lm instead.

Elai

On Thu, Feb 9, 2012 at 1:42 PM, Michael Friendly <friendly at yorku.ca> wrote:
> I'm trying to write some functions extending influence measures to
> multivariate linear models and also
> allow subsets of size m>=1 to be considered for deletion diagnostics.  I'd
> like these to work roughly parallel
> to those functions for the univariate lm where only single case deletion
> (m=1) diagnostics are considered.
>
> Corresponding to stats::hatvalues.lm, the S3 method for class "lm" objects,
>
>> hatvalues <-function (model, ...)
> UseMethod("hatvalues")
>
>> hatvalues.lm <-
> function (model, infl = lm.influence(model, do.coef = FALSE),    ...)
> {
>    hat <- infl$hat
>    names(hat) <- names(infl$wt.res)
>    hat
> }
>
> I have, for class "mlm" objects
>
> hatvalues.mlm <- function(model, m=1, infl=mlm.influence(model, m=m, do.coef
> = FALSE), ...)
> {
>    hat <- infl$H
>    m <- infl$m
>    names(hat) <- if(m==1) infl$subsets else apply(infl$subsets,1, paste,
> collapse=',')
>    hat
> }
>
> where mlm.influence() does the calculations, but also allows the m= argument
> to specify subset size.
> Yet when I test this I can't seem to pass the m= argument directly, so that
> it gets stuffed in to the infl=
> call to mlm.influence.
>
> # fit an mlm
> library(heplots)
> Rohwer2 <- subset(Rohwer, subset=group==2)
> rownames(Rohwer2)<- 1:nrow(Rohwer2)
> Rohwer.mod <- lm(cbind(SAT, PPVT, Raven) ~ n+s+ns+na+ss, data=Rohwer2)
>
>> class(Rohwer.mod)
> [1] "mlm" "lm"
>
>
> ## this doesn't work, as I would like it to, calling the hatvalues.mlm
> method, but passing m=2:
>> hatvalues(Rohwer.mod, m=2)
> Error in UseMethod("hatvalues") :
>  no applicable method for 'hatvalues' applied to an object of class
> "c('double', 'numeric')"
>
> I don't understand why this doesn't just call hatvalues.mlm, since
> Rohwer.mod is of class "mlm".
>
> # These work -- calling hatvalues.mlm explicitly, or passing the infl=
> argument with the call to
> # mlm.influence
>> hatvalues.mlm(Rohwer.mod, m=2)
>> hatvalues(Rohwer.mod, infl=mlm.influence(Rohwer.mod,m=2))
>
> Can someone help me understand what is wrong and how to make the .mlm method
> allow m= to be passed
> directly to the infl= computation?
>
> thx,
> -Michael
>
> --
> Michael Friendly     Email: friendly AT yorku DOT ca
> Professor, Psychology Dept.
> York University      Voice: 416 736-5115 x66249 Fax: 416 736-5814
> 4700 Keele Street    Web:   http://www.datavis.ca
> Toronto, ONT  M3J 1P3 CANADA
>
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