From m@echler @ending from @t@t@m@th@ethz@ch  Wed Oct 17 16:14:50 2018
From: m@echler @ending from @t@t@m@th@ethz@ch (Martin Maechler)
Date: Wed, 17 Oct 2018 16:14:50 +0200
Subject: [Rd] methods(class = class(<obj>)) - improve for |cl.| > 1  ?
Message-ID: <23495.17370.834231.288292@stat.math.ethz.ch>

With new "strict" settings in R-devel, the following glm() example

> data(anorexia, package = "MASS")
> fm <- glm(Postwt ~ Prewt + Treat + offset(Prewt), family = gaussian, data = anorexia)
> methods(class = class(fm))
Warning in grep(name, row.names(info)) :
  argument 'pattern' has length > 1 and only the first element will be used
Warning in gsub(name, "", row.names(info)) :
  argument 'pattern' has length > 1 and only the first element will be used
Warning in grep(pattern, all.names, value = TRUE) :
  argument 'pattern' has length > 1 and only the first element will be used
Warning in grep(pattern, all.names, value = TRUE) :
  argument 'pattern' has length > 1 and only the first element will be used
...........
...........
...........
[ca. 20 lines of warnings]

and then shows the "glm" methods, but not "lm" ones.

This is not a bug strictly, as  ?methods says that

   class: a symbol or character string naming a class: only used if
          ?generic.function? is not supplied.

and so the use of

       	   methods(class = class(<obj>))

is a user error when  class(<obj>)  is of length > 1.

In the case of e.g. a randomForest() result, we also get 25
warnings, i.e. 50 lines, but then

--->>>  no methods found

because

   > class(rf.fit)
   [1] "randomForest.formula" "randomForest"

and no methods are  defined for "randomForest.formula".

---

Of course, all this works fine with S4 classes:  There the full
inheritance is used and all methods are found.

Still, would it make sense to improve the underlying .S3methods() ?

I assume it will break *some* overzealous package checks out
there when .S3methods() and hence methods() would return *more*
in such case.

Comments?

--
Martin Maechler
ETH Zurich  and  R Core



[Rd] methods(class = class(<obj>)) - improve for |cl.| > 1 ?
Martin Maechler