Howdy all,
I have a problem that I'd like some advice/help in solving---it has to do
with R's pass-by-value system. I understand the issue, but am wondering if
anyone has found a working solution in dealing with it for cases when one
wants to modify an object inside of a method, specifically when working with
S4. I'm aware that R.oo is able to deal with this using S3, but I'd
really
rather stick to S4.
The basics of what I would like to do are coded below:
setClass("MyMatrix",
representation(
parameters="matrix",
uniqueCount="numeric"
),
prototype(
parameters=matrix(numeric(0),0,0),
uniqueCount=1
)
)
setGeneric("createUniqueName", function(object)
standardGeneric("createUniqueName"))
setMethod("createUniqueName", "MyMatrix", function(object){
retval <- paste("unique_", object at uniqueCount,
sep="")
object at uniqueCount <- object at uniqueCount + 1
return(retval)
})
x <- new("MyMatrix", parameters=matrix(0, 2, 2))
createUniqueName(x) # returns "unique_1"
x # x at uniqueCount is still 1
I understand why this is happening, but am wondering how people in the
community have dealt with it, specifically when using S4. Any advice would
be appreciated. Also, I am aware that this is somewhat of a silly example,
but it should allow you to see what I'm trying to accomplish.
Thank you,
Jeff.
--
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Sent from the R help mailing list archive at Nabble.com.
Hi Jeff --
two different scenarios are to overwrite the current object, along the
lines of
y <- uniquify(y)
where uniquify is a method like createUniqueName but returns the
(modified) instance rather than unique name
setMethod('uniquify', 'MyMatrix', function(x) {
x at uniqueCount <- # something unique
x
})
The second is a replacement method, along the lines of
setGeneric("uniqueCount<-",
function(x, ..., value) standardGeneric("uniqueCount<-"))
setReplaceMethod("uniqueCount",
signature=c(x="MyMatrix", value="numeric"),
function(x, ..., value) {
x at uniqueCount <- value
x
})
uniqueCount(x) <- uniqueCount(x) + 1
x # now modified
This is untested psuedo-code, so I hope it's right enough to get you
going.
Martin
Jeffrey Spies <jspies2008 at gmail.com> writes:
> Howdy all,
>
> I have a problem that I'd like some advice/help in solving---it has to
do
> with R's pass-by-value system. I understand the issue, but am
wondering if
> anyone has found a working solution in dealing with it for cases when one
> wants to modify an object inside of a method, specifically when working
with
> S4. I'm aware that R.oo is able to deal with this using S3, but
I'd really
> rather stick to S4.
>
> The basics of what I would like to do are coded below:
>
> setClass("MyMatrix",
> representation(
> parameters="matrix",
> uniqueCount="numeric"
> ),
> prototype(
> parameters=matrix(numeric(0),0,0),
> uniqueCount=1
> )
> )
>
> setGeneric("createUniqueName", function(object)
> standardGeneric("createUniqueName"))
>
> setMethod("createUniqueName", "MyMatrix",
function(object){
> retval <- paste("unique_", object at uniqueCount,
sep="")
> object at uniqueCount <- object at uniqueCount + 1
> return(retval)
> })
>
> x <- new("MyMatrix", parameters=matrix(0, 2, 2))
> createUniqueName(x) # returns "unique_1"
> x # x at uniqueCount is still 1
>
> I understand why this is happening, but am wondering how people in the
> community have dealt with it, specifically when using S4. Any advice would
> be appreciated. Also, I am aware that this is somewhat of a silly example,
> but it should allow you to see what I'm trying to accomplish.
>
> Thank you,
>
> Jeff.
>
>
> --
> View this message in context:
http://www.nabble.com/S4-pass-by-value-work-around--tp17997553p17997553.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> 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 M2 B169
Phone: (206) 667-2793
Quick comment. Use an environment to hold your "fields" and then pass around the environment variable. Any modification to variables inside the environment done from anywhere (inside/outside functions) will be persistent. Then wrap this up in a class structure, overload, say, '$', '[[', '$<-', '[[<-' to get() and assign() to your object and you have the first seed of what is done in R.oo. Note that '$' are '$<-' indeed available for environments. However, it is not recommended to extend the environment class itself. Instead you should wrap the environment up in a list and work from that. Search the R mailing list archives for issues you would/will face if you inherit from environment. My $.02 Henrik (R.oo author) On Wed, Jun 18, 2008 at 10:26 PM, Jeffrey Spies <jspies2008 at gmail.com> wrote:> > Howdy all, > > I have a problem that I'd like some advice/help in solving---it has to do > with R's pass-by-value system. I understand the issue, but am wondering if > anyone has found a working solution in dealing with it for cases when one > wants to modify an object inside of a method, specifically when working with > S4. I'm aware that R.oo is able to deal with this using S3, but I'd really > rather stick to S4. > > The basics of what I would like to do are coded below: > > setClass("MyMatrix", > representation( > parameters="matrix", > uniqueCount="numeric" > ), > prototype( > parameters=matrix(numeric(0),0,0), > uniqueCount=1 > ) > ) > > setGeneric("createUniqueName", function(object) > standardGeneric("createUniqueName")) > > setMethod("createUniqueName", "MyMatrix", function(object){ > retval <- paste("unique_", object at uniqueCount, sep="") > object at uniqueCount <- object at uniqueCount + 1 > return(retval) > }) > > x <- new("MyMatrix", parameters=matrix(0, 2, 2)) > createUniqueName(x) # returns "unique_1" > x # x at uniqueCount is still 1 > > I understand why this is happening, but am wondering how people in the > community have dealt with it, specifically when using S4. Any advice would > be appreciated. Also, I am aware that this is somewhat of a silly example, > but it should allow you to see what I'm trying to accomplish. > > Thank you, > > Jeff. > > > -- > View this message in context: http://www.nabble.com/S4-pass-by-value-work-around--tp17997553p17997553.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help at r-project.org mailing list > 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. >