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?)
It seems to happen in locales UTF-8, POSIX and C. I have not tried others.
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.
Yes, I do have the impression that print() does not do exactly what one
might like when it finds an S4 attribute in an S3 object. I hope this is
not a design decision. It would make it very difficult to migrate toward
S4 if it is not possible to include S4 objects in S3 objects this way.
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.)
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