search for: iss4object

Dear r-help list members, Is there a way to test whether an object is an S4 object? The best that I've been able to come up with is isS4object <- function(object) !(is.null(slotNames(object))) which assumes that an S4 object has at least one slot. I think this is safe, but perhaps I'm missing something. Thanks, John -------------------------------- John Fox Department of Sociology McMaster University Hamilton, Ontario Canada L8...

Dear r-help list members, Is there a way to test whether an object is an S4 object? The best that I've been able to come up with is isS4object <- function(object) !(is.null(slotNames(object))) which assumes that an S4 object has at least one slot. I think this is safe, but perhaps I'm missing something. Thanks, John -------------------------------- John Fox Department of Sociology McMaster University Hamilton, Ontario Canada L8...

...ass. See the setOldClass help page.) 2. There is a heuristic test for S4 objects, seemsS4Object(), and a corresponding C-level test, R_seemsS4Object(object), both using the existence of a "package" attribute on class(object) as a test. The test is called seemsS4Object() rather than isS4Object() deliberately, but it should be fairly accurate. It will mistakenly identify an S3 object as S4 if the package attribute is there (possible, but hard to see why anyone would do this). It can make the opposite mistake, though, UNLESS the package generating the object is reinstalled with the cur...