Bengoechea Bartolomé Enrique (SIES 73) wrote:
Forgot to answer this one:
It would seem natural that metadata associated with one dimension:
would a table-like object
[thanks for reading through what seems much like a telescoped sentences]
Right. A data frame has the problem that for most use cases one would
want that each dimension length matches the *rows* of the data frame
instead of the columns, but it is the columns what we would have "for
free" when allowing "dimmeta" elements to be lists...
Think of one data.frame per dimension and each data.frame having its
rows aligned along that dimension.
In the case of a matrix, the dim-1 data.frame would have as many rows as
rows in the matrix and the dim-2 data.frame would have as many rows as
columns in the matrix.
When thinking in terms of generalization, one can also note that the
one-dimension case can already be modelled by a data.frame.
L.
Enrique
-----Original Message----- From: Laurent Gautier
[mailto:lgaut...@gmail.com] Sent: jueves, 09 de julio de 2009 14:15
Cc: Heinz Tuechler; Bengoechea Bartolomé Enrique (SIES 73); Tony
Plate; Henrik Bengtsson; r-devel@r-project.org Subject: Re: [Rd]
Suggestion: Dimension-sensitive attributes
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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