On 2/11/2012 12:00 PM, ilai wrote:
You are setting a new class ("inflmlm") at the end of mlm.influence.
Remove that second to last line and enjoy your new S3 method.
Thanks for the suggestion, but it doesn't help -- I still get the same
behavior whether mlm.influence returns a classed object or not.
As well, I am defining print.inflmlm() and as.data.frame.inflmlm()
methods for these objects, so I do need mlm.influence to return a
classed object.
My hatvalues.mlm is designed to be similar in structure to
stats::hatvalues.lm where the S3 generic is defined.
hatvalues.mlm <- function(model, m=1, infl, ...)
{
if (missing(infl)) {
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
}
> hatvalues
function (model, ...)
UseMethod("hatvalues")
<bytecode: 0x0326fd30>
<environment: namespace:stats>
> hatvalues.lm
function (model, infl = lm.influence(model, do.coef = FALSE),
...)
{
hat <- infl$hat
names(hat) <- names(infl$wt.res)
hat
}
<bytecode: 0x0326de6c>
<environment: namespace:stats>
The idea is that the infl= argument specifies a call to the
computational function, mlm.influence() in my case, just as
lm.influence() does in the stats package.
The logic of UseMethod is that it should dispatch on the class of the
*first* argument to the function, which in my test case is c("mlm", "lm")
> Rohwer.mod <- lm(cbind(SAT, PPVT, Raven) ~ n+s+ns+na+ss, data=Rohwer2)
> class(Rohwer.mod)
[1] "mlm" "lm"
> trace(hatvalues)
> hatvalues(Rohwer.mod, m=2)
trace: hatvalues(Rohwer.mod, m = 2)
Error in UseMethod("hatvalues") :
no applicable method for 'hatvalues' applied to an object of class
"c('double', 'numeric')"
> hatvalues(Rohwer.mod)
trace: hatvalues(Rohwer.mod)
1 2 3 4 5 6
7 8
0.16700926 0.21845327 0.14173469 0.07314341 0.56821462 0.15432157
0.04530969 0.17661104
...
I'm still stumped on why with the extra argument m=2, R sees this
as an object of class c('double', 'numeric'). As well, I can't see
any way to debug this.
I'm not sure, but I think it is just the new class "inflmlm" applied
to inf in the formals of hatvalues.mlm confused the dispatch
mechanism. You would think the error message will call the offending
class not "numeric" double" but that's above my pay grade...
You could probably put back the inflmlm class assignment with an
explicit call to UseMethod in hatvalues.mlm ?
Cheers
On Fri, Feb 10, 2012 at 2:35 PM, Michael Friendly<frien...@yorku.ca> wrote:
On 2/10/2012 4:09 PM, Henrik Bengtsson wrote:
So people may prefer to do the following:
hatvalues.mlm<- function(model, m=1, infl, ...)
{
if (missing(infl)) {
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
}
Thanks; I tried exactly that, but I still can't pass m=2 to the mlm method
through the generic
hatvalues(Rohwer.mod)
1 2 3 4 5 6 7
8
0.16700926 0.21845327 0.14173469 0.07314341 0.56821462 0.15432157 0.04530969
0.17661104
9 10 11 12 13 14 15
16
0.05131298 0.45161152 0.14542776 0.17050399 0.10374592 0.12649927 0.33246744
0.33183461
17 18 19 20 21 22 23
24
0.17320579 0.26353864 0.29835817 0.07880597 0.14023750 0.19380286 0.04455330
0.20641708
25 26 27 28 29 30 31
32
0.15712604 0.15333879 0.36726467 0.11189754 0.30426999 0.08655434 0.08921878
0.07320950
hatvalues(Rohwer.mod, m=2)
Error in UseMethod("hatvalues") :
no applicable method for 'hatvalues' applied to an object of class
"c('double', 'numeric')"
## This works:
hatvalues.mlm(Rohwer.mod, m=2)
... output snipped
hatvalues
function (model, ...)
UseMethod("hatvalues")
<bytecode: 0x021339e4>
<environment: namespace:stats>
-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
--
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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