Starting by working on an interface for such object(s) is probably the
first step toward a unified solution, and this before about if and how R
attributes are used.
It would also help to ensure a smooth transition from the existing
classes implementing a similar solution (first the interface is added to
those classes, then after a grace period the classes are eventually
refactored).
Dimension-level is what seems to the be most needed... but I am not
convinced of the practicality of the object-level, and cell-level scheme
s proposed:
- Object-level, if not linked to any dimension-attribute is such saying
that one want to attach anything to any object. That's what attr() is
already doing.
- Cell-level, is may be out-of-scope for one first trial (but may be I
missed the use-cases for it)
If starting with behaviour, it seems to boil to having "["/"[<-" and
"dimmeta()"/"dimmeta<-()", :
- extract "[" / replace "[<-" :
* keeps working the way it already does
* extracts a subset of the object as well as a subset of the
dimension-associated metadata.
* departing too much from the way "[" is working and add
behind-the-curtain name matching will only compromise the chances of
adoption.
* forget about the bit about which metadata is kept and which one
isn't when using "[". Make a function "unmeta()" (similar behavior to
"unname()") to drop them all, or work it out with something like
> dimmeta(x, 1) <- NULL # drop the metadata associated with dimension 1
- access the dimension-associated metadata:
* may be a function called "dimmeta()" (for consistency with
"dimnames()") ? The signature could be dimmeta(x, i), with x the object,
and i the dimension requested. A replace function "dimmeta<-"(x, i,
value) would be provided.
In the abstract the "names" associated with a given dimension is just
one of possible metadata, but I'd keep away from meddling with it for a
start.
It would seem natural that metadata associated with one dimension:
would a table-like object (data.frame seems natural in R, and
unfortunately there is no data.frame-like structure in R).
L.
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