[Rd] Error in "getClass" when calling the function "show"

[Prof Brian Ripley]

On Tue, 10 Jun 2008, Laurent Gautier wrote:

> 2008/6/10 Prof Brian Ripley <ripley at stats.ox.ac.uk>:
>> showDefault has
>>
>>    clDef <- getClass(class(object))
>>
>> Looks like the showDefault code intended
>>
>>    clDef <- getClass(class(object), .force=TRUE)
>>
>> However, why are you calling show() on a non-S4 object?  I cannot see any
>> advtanges in doing so.
>
> I'd like *one* printing method for all objects, and the generic "show"
> is registered as working for ANYthing (see below) ?

print() calls show() for S4 objects (with no additional arguments).

I agree show() ought to do what it is documented to, but calling it on 
non-S4 objects is inefficient.

> Or is defining one's own function currently recommended ?
>
> myPrint <- function(x, ...)
> {
>  if (isS4(x)) {
>    show(x, ...)
>  } else {
>    print(x, ...)
>  }
> }
>
>> showMethods("show")
> Function: show (package methods)
> object="ANY"
> object="classRepresentation"
> object="derivedDefaultMethod"
>    (inherited from: object="MethodDefinition")
> object="function"
>    (inherited from: object="ANY")
> object="genericFunction"
> object="MethodDefinition"
> object="MethodsList"
>    (inherited from: object="ANY")
> object="MethodWithNext"
> object="ObjectsWithPackage"
> object="signature"
> object="traceable"
>
>> showMethods("print")
>
> Function "print":
> <not a generic function>
>> getMethod("show", "ANY")
> Method Definition (Class "derivedDefaultMethod"):
>
> function (object)
> showDefault(object, FALSE)
> <environment: namespace:methods>
>
> Signatures:
>        object
> target  "ANY"
> defined "ANY"
>
>
>> On Tue, 10 Jun 2008, Laurent Gautier wrote:
>>
>>> Dear List,
>>>
>>> Calling "show" on an object of class "summary.lm" gives:
>>> Error in getClass(class(object)) : "summary.lm" is not a defined class
>>>
>>> Is this a miss on my end ?
>>>
>>>
>>>> x <- seq(1, 10)
>>>> show(x)
>>>
>>> [1]  1  2  3  4  5  6  7  8  9 10
>>>>
>>>> y <- runif(10)
>>>> fit <- lm(y ~ x)
>>>> show(fit)
>>>
>>> Call:
>>> lm(formula = y ~ x)
>>>
>>> Coefficients:
>>> (Intercept)            x
>>>   1.04938     -0.08869
>>>
>>>> show(summary(fit))
>>>
>>> Error in getClass(class(object)) : "summary.lm" is not a defined class
>>>>
>>>> class(summary(fit))
>>>
>>> [1] "summary.lm"
>>>>
>>>> class((fit))
>>>
>>> [1] "lm"
>>>>
>>>> getClass("lm")
>>>
>>> Virtual Class
>>>
>>> No Slots, prototype of class "S4"
>>>
>>> Extends: "oldClass"
>>>
>>> Known Subclasses:
>>> Class "mlm", directly
>>> Class "aov", directly
>>> Class "glm", directly
>>> Class "maov", by class "mlm", distance 2
>>> Class "glm.null", by class "glm", distance 2
>>>>
>>>> getClass("summary.lm")
>>>
>>> Error in getClass("summary.lm") : "summary.lm" is not a defined class
>>>>
>>>> sessionInfo()
>>>
>>> R version 2.7.0 Patched (2008-06-07 r45877)
>>> i686-pc-linux-gnu
>>>
>>> locale:
>>>
>>> LC_CTYPE=en_US.UTF-8;LC_NUMERIC=C;LC_TIME=en_US.UTF-8;LC_COLLATE=en_US.UTF-8;LC_MONETARY=C;LC_MESSAGES=en_US.UTF-8;LC_PAPER=en_US.UTF-8;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=en_US.UTF-8;LC_IDENTIFICATION=C
>>>
>>> attached base packages:
>>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>>
>>>
>>> Laurent
>>>
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>
>> --
>> Brian D. Ripley,                  ripley at stats.ox.ac.uk
>> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
>> University of Oxford,             Tel:  +44 1865 272861 (self)
>> 1 South Parks Road,                     +44 1865 272866 (PA)
>> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>>
>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595