[R] Extracting Coefficients and Such from mle2 Output

Ben Bolker bolker at ufl.edu
Mon Feb 2 01:17:53 CET 2009

Marc Schwartz <marc_schwartz <at> comcast.net> writes:

> on 02/01/2009 10:45 AM David Winsemius wrote:
> > Let me  admit at this point that I am not really sure that S4 classes is
> > the correct classification of such "@"-using extraction processes. The
> > documentation refers to "formal methods" and I don't yet have enough
> > knowledge to know that how tightly slots and formal classes are linked
> > with S4 or S3.
> David,
> The use of '@' as a slot extractor is specific to S4 methods and you
> will actually get an error if attempting to use it on other object
> types. As per the Details section of ?"@":

  My other two cents about this issue:

 David is quite right that you can basically think of "@"
as equivalent to "$" for getting bits out of S4 objects.
However ... in general S4 classes make it harder to get
internal bits out of objects, and in some sense they're
really *supposed* to make it harder.  Really the thing to
do when you encounter information that's buried somewhere
in an S4 object, the appropriate solution is what you did --
write to the author and say "why isn't there an accessor
method [the technical jargon for functions like coef()]
to get this piece of information out of this object, or
why isn't it properly documented? (Or is there some 
reason that I shouldn't be trying to access this piece
of information?)"

   Ben Bolker

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