Worked like a charm!!  Thank you so much.  I just plugged the following into
my code ...

setMethod("$", "CADresponses", function(x, name) slot(x, name))

... and it worked perfect.  If you don't mind, I have a quick follow up
question, using your example

setClass("A", representation(a="numeric", b="numeric"))
setMethod("$", "A", function(x, name) slot(x, name))
data = new("A", a=1:10, b=1:10)
data$a[5] #now works thanks to your code
data$a[5] <- 200 #assignments do not work -- any ideas?
data[5,c("a")] = 200 #would also like this to work -- any ideas?

Do you have any suggestions for getting assignments and brackets to work as
they would for data frames?  Thanks so much for your help.
Best,
Markus



On Mon, Feb 8, 2010 at 2:44 PM, Martin Morgan <mtmorgan@fhcrc.org> wrote:

> On 02/07/2010 08:31 PM, Markus Weisner wrote:
> > I created some S4 objects that are essentially data frame objects.  The
> S4
> > object definitions were necessary to verify data integrity and force a
> > standardized data format.  I am, however, finding myself redefining all
> the
> > typical generic functions so that I can still manipulate my S4 objects as
> if
> > they were data frames ... I have used setMethod to set methods for
> "subset",
> > "head", and "tail".  I would like to use setMethod or setGeneric to
> enable
> > me to use object$slotname to access object@slotname for my S4 objects.
>  Any
> > advice is appreciated.  Thanks.
>
> Hi Markus --
>
> > setClass("A", representation(a="numeric"))
> [1] "A"
> > new("A")$a
> Error in new("A")$a : $ operator not defined for this S4 class
> > getGeneric("$")
> standardGeneric for "$" defined from package "base"
>
> function (x, name)
> standardGeneric("$", .Primitive("$"))
> <environment: 0xa62028>
> Methods may be defined for arguments: x
> Use  showMethods("$")  for currently available ones.
> > setMethod("$", "A", function(x, name) slot(x, name))
> [1] "$"
> > new("A", a=1:10)$a
>  [1]  1  2  3  4  5  6  7  8  9 10
> > new("A", a=1:10)$b
> Error in slot(x, name) : no slot of name "b" for this object of class "A"
>
> does that help?
>
> Martin
>
> > --Markus
> >
> >       [[alternative HTML version deleted]]
> >
> > ______________________________________________
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> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>
>
> --
> Martin Morgan
> Computational Biology / Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N.
> PO Box 19024 Seattle, WA 98109
>
> Location: Arnold Building M1 B861
> Phone: (206) 667-2793
>

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