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'"ts" treated as a registered S3 class, but keep its "structure" behaviour' ?

2 messages · Yohan Chalabi, John Chambers

Original
Yohan Chalabi
# 
Dear all,

In R-devel I have noticed the new approach for the "ts" class in the
package "methods".

the "structure" behaviour of "ts" is not always kept when one uses
"ts" objects and objects of classes which extend the virtual class
"structure".

As a short example:

## this works fine
setClass("foo", representation(header = "character"), contains = "structure")
foo <- new("foo", 1:10, header = "foo")
ts <- ts(1:10)
foo / ts

## but the problem appears when one defines an "Ops" method for class "foo"
setMethod("Ops", c("foo", "foo"),
           function(e1, e2) {
               .Data <- callGeneric(e1 at .Data, e2 at .Data)
               header <- paste(e1 at header, e2 at header, sep = "_")
               new("foo", .Data, header = header)
           })
foo <- new("foo", 1:10, header = "foo")
foo + foo
ts <- ts(1:10)
foo / ts
# Error in getDataPart(1:10) : no '.Data' slot defined for class "ts"

Is this the expected behavior?

regards,
Yohan

--
PhD student
Swiss Federal Institute of Technology
Zurich

www.ethz.ch
John Chambers
#
Yohan Chalabi wrote:
No, not expected.  It may take some special treatement to fix it, though.

Your subject heading is indeed the problem.  Normally, the structure of 
an S3 class is a black box, and no S4 slots should usually be associated 
with it when it's registered via setOldClass.

However, just because "ts" does want to be a "structure" class, it would 
be nice to give it a .Data slot.  I'll experiment with this and see if 
it causes other things to break immediately.

Thanks for the report.

John Chambers