Certainly this _is_ possible. However, there are no built-in functions to do
just this (that I know of). Here's a function that attaches like you say (but
still makes a local copy)
attachslot <- function(x) {
xname <- substitute(x)
sl <- names(getSlots(class(x)))
slotnames <- paste(sl, " <<- ", xname, "@", sl, sep = "")
for (i in slotnames) {
eval(parse(text = substitute(slotnames, list(slotnames = slotnames))))
}
}
If you wanted to do this without making a local copy, then the strategy might
be either to make a promise object out of the "slotname" (which stores only the
unevaluated expression until you need the data), see ?delay, or a bit more
complicated, store the "name" of the object as a pointer to the underlying
slot. Then, you would be referencing the pointer to the object rather than the
copy. Don't want to spend the time to figure this out, but I'm pretty sure it
_can_ be done.
All this said, there are good reasons not to attach like this as it is
certainly a bad coding habit. If your code ever references two objects of the
same class, there might be confusion as to which one is attached as slots are
not unique. Also, this relies on the class design and not on the underlying
data. I would certainly (and do!) want to switch around my slots or classes
without substantively rewriting my code. And lastly, if you ever had an object
named x and a slot of an attached object named x then either the former would
be rewritten, or you'd have to spend a great deal of time figuring out ways to
properly scope your attached slots.
In short, don't do it.
Best,
Robert
-----Original Message-----
From: F.Tusell [mailto:[EMAIL PROTECTED]
Sent: Tuesday, January 18, 2005 9:38 AM
To: [email protected]
Subject: [R] "Attach" for S4 objects?
When passing a list as an argument to a function, I find it convenient
to attach it in the first line of th function code, then refer to the
components as A, B, etc. rather than as list$A, list$B, etc.
If I pass a S4 class object, is there a way to "attach" it, or do I have
to refer to the slots as [EMAIL PROTECTED], [EMAIL PROTECTED], etc.?
I could always make copies,
A <- [EMAIL PROTECTED]
B <- [EMAIL PROTECTED]
...
but "object" has many slots, some fairly large, so this seems wasteful.
Thank you.
--
Fernando TUSELL e-mail:
Departamento de Econometr�a y Estad�stica [EMAIL PROTECTED]
Facultad de CC.EE. y Empresariales Tel: (+34)94.601.3733
Avenida Lendakari Aguirre, 83 Fax: (+34)94.601.3754
E-48015 BILBAO (Spain) Secr: (+34)94.601.3740
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