Re: [Rd] S4 / S3 / Sweave problem

>>>>> "PaulG" == Paul Gilbert <pgilbert_at_bank-banque-canada.ca> >>>>> on Sun, 04 May 2008 21:46:18 -0400 writes:

    PaulG> Prof Brian Ripley wrote:

    >> 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
    >> 

    >> $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.

    PaulG> Yes, I do have the impression that print() does not do exactly what one 
    PaulG> might like when it finds an S4 attribute in an S3 object. I hope this is 

I'm pretty sure that this has *not* been a design decision, but rather an oversight till now.

To me, it seems even a "natural" oversight: If you are working for fully designed classes, it seems awkward to simultaneously use attributes of S3- (or "no class"-) objects. I do understand though that there can be situations, in particular migrations ones, where you want to do this ... and should be allowed to and should see print() working.

Martin

    >> On Sun, 4 May 2008, Paul Gilbert wrote:
    >> 

    >> 
    >> 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).
    >> 

    >>>> z <- new("TSmetax", serIDs="whatever", ExtractionDate= NULL)
    >>>> print(z)

    >>>> zz <- ts(1:10)
    >>>> attr(zz, "Meta") <- z
    >>>> print(zz)

    >>>> 

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