You can find this info using the function nargs(). I've used this with S3 classes, and as far as I know it should work with S4 classes too. See ?nargs for examples.
-- Tony Plate Bradley Buchsbaum wrote: > Hi, > > I am working on writing some S4 classes that represent > multidimensional (brain) image data. I would like these classes to > support standard array indexing. I have been studying the Matrix and > EBImage (http://www.bioconductor.org/packages/1.9/bioc/html/EBImage.html) > packages to see how this is done. > > When using objects of the "array" class directly, R distinguishes > between the calls: > > x[i,,] and x[i] > > with the former returning a 2D array of values and the latter > returning a single value. The question I have is whether this same > behavior can be simulated in classes that do not inherit from the > "array" class directly? (See below for a snippet from the EBImage > package which suggests that it cannot). > > My guess is that native array indexing is making use of the > information provided by the commas, and this is unavailable to user > implemented class methods? > > thanks, > > Brad Buchsbaum > > > > # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - > setMethod("[", signature(x = "Image", i = "numeric", j = "missing"), > function(x, i, j, k, ..., drop) { > if (missing(k)) { > warning("using index [int], cannot distinguish from > [int,,ANY], use [int,1:dim(x)[2],ANY] otherwise") > tmp = [EMAIL PROTECTED], drop = FALSE] > } > else { > tmp = [EMAIL PROTECTED], , k, drop = FALSE] > } > ... > } > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
