[R] passing an extra argument to an S3 generic

[Michael Friendly]

On 2/9/2012 6:24 PM, ilai wrote:
> 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.

No, I've written an S3 method, influence.mlm and a computational method,
mlm.influence, both of which take an m= argument.  I didn't post all the 
code because I thought the question might have an easy answer based on 
what I provided.

I include all the code and a test case in the attached .txt file that
can be sourced.

-Michael

>
> 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
>>
>> ______________________________________________
>> R-help at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>


-- 
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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