Re: [Rd] S4 / S3 / Sweave problem

I'm not sure what the issue being asked about here is. The peculiar printing I don't see and may well be a locale issue. (Is this UTF-8 and TeX has not been told so?)

The other issue is that when printing an object with attributes, there is no consideration of S4 classes amongst the attributes. That was either an undocumented design decision or an omission. This is different from

> print(attributes(zz))

$tsp
[1] 1 10 1

$class
[1] "ts"

$Meta
An object of class “TSmetax”
Slot "serIDs":
[1] "whatever"

Slot "ExtractionDate":
NULL since although attributes are internally a pairlist and printed by a special C function, attributes() returns a list.

It would be fairly easy to include a branch for S4 objects, but there are ambuiguities still over what they are (I wrote up a set of questions over a year ago about this). But it would seem fairly safe to send them to show() in the same circumstances that autoprinting does for apparently S4 objects.

On Sun, 4 May 2008, Paul Gilbert wrote:

> I'm not sure if this as a bug or something I am doing wrong. It occurs in
> both 2.7.0 and 2.6.2.

My guess is that it was never intended that S4 objects be used as attributes, in the same way that one of the unanswered questions is if S4 objects should be allowed to have attributes (other than slots).

>
> require("methods")
>
> setClassUnion("OptionalPOSIXct", c("POSIXct", "NULL"))
>
> setClass("TSmetax",
> representation(serIDs="character", ExtractionDate="OptionalPOSIXct" ))
>
> setGeneric("TSmetax",
> def= function(x, ...) standardGeneric("TSmetax"))
>
> setMethod("TSmetax", signature(x="character"),
> definition= function(x, ...){
> new("TSmetax", serIDs=x, ExtractionDate=Sys.time())
> } )
>
>> z <- new("TSmetax", serIDs="whatever", ExtractionDate= NULL)
>> print(z)
> An object of class "TSmetax"
> Slot "serIDs":
> [1] "whatever"
>
> Slot "ExtractionDate":
> NULL
>
> Now if I make this an attribute of an S3 class an print, I get
>> zz <- ts(1:10)
>> attr(zz, "Meta") <- z
>> print(zz)
> Time Series:
> Start = 1
> End = 10
> Frequency = 1
> [1] 1 2 3 4 5 6 7 8 9 10
> attr(,"Meta")
> <S4 Type Object>
> attr(,"serIDs")
> [1] "whatever"
> attr(,"ExtractionDate")
> `
NULL
`
> attr(,"class")
> [1] "TSmetax"
> attr(,"class")attr(,"package")
> [1] ".GlobalEnv"
>>
>
> The `
NULL
` shows up i
> shows up in the tex file generated by a vignette as
> <soh>NULL<soh> which causes tex (pdftex) to throw an error.
> (It also seems to mess up my mail tool, so I hope this goes through.)

-- 
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




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