Suggestion: Dimension-sensitive attributes
Bengoechea Bartolom? 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:lgautier at gmail.com] Sent: jueves, 09 de julio de 2009 14:15 Cc: Heinz Tuechler; Bengoechea Bartolom? Enrique (SIES 73); Tony Plate; Henrik Bengtsson; r-devel at 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.