On Sun, 13 Aug 2006, Seth Falcon wrote: > "miguel manese" <[EMAIL PROTECTED]> writes: > > > Hello, > > > > I created an S3 "type" w/c is actually a list that should look like a > > matrix but whose data is actually in an external file. The SEXP just > > contains info on how to retrieve the data from the file. When I get to > > the part of creating the SEXP, I found out that SET_DIM & SET_DIMNAME > > checks the SEXP if the length matches (somewhere in src/main/attrib.c, > > dimgets & dimnamegets IIRC (it's on my other partition. life sucks)). > > After a quick look at the R code, I tried to bypass them by doing: > > If you want to emulate a matrix-like object you might want to look > at the Matrix package which does uses S4 classes to represent > matrices.
My guess (from earlier messages) is that the issue is rather that of an S3 class akin to "data.frame". > I don't think the class systems are fully functional at the C-level of > R; macros like SET_DIM don't do dispatch beyond the built-in SEXP > types. They do no dispatch at all. Rather, they are part of the internals of attr<-, invoked e.g. by attr(x, "dim") <- newdim. The class system is fully functional at a higher level in C, e.g. do_dimgets. This is part of the internal integrity checks on attributes (and documented in detail in the R-exts manual in the R-devel version of R). Please don't use a "dim" attribute when those checks would be inappropriate, as code is written to rely on them. E.g. a data frame does not have such an attribute, but does have a dim() method (but not a dim<-() method). -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
