[R] OOP and passing by value

[Joris Meys]

by returning the object ?

setMethod("setData","test",
 function(this,fcn,k){
   this at t <- as.numeric(seq(-k,k))/(2*k+1)
   this at f <- sapply(this at t,FUN=fcn)   #changed!
   return(this)                                          #changed!
 }
)

#-----------------------------------------------------------
> tst <- new("test")
> fcn <- function(u){ sin(2*pi*u) }
> New <- setData(tst,fcn,5)
> New at t
[1] -0.4545455 -0.3636364 -0.2727273 -0.1818182 -0.0909091  0.0000000
0.0909091  0.1818182  0.2727273  0.3636364  0.4545455


On Wed, Jun 9, 2010 at 2:28 PM, michael meyer <mjhmeyer at googlemail.com> wrote:
> Greetings,
>
> I love the R system and am sincerely grateful for the great effort the
> product and contributors
> are delivering.
>
> My question is as follows:
>
> I am trying to use S4 style classes but cannot write functions that modify
> an object
> because paramter passing is by value.
> For example I want to do this:
>
> setGeneric("setData", function(this,fcn,k){ standardGeneric("setData") })
>
> setClass(
>  "test",
>  representation(f="numeric", t="numeric")
> )
> setMethod("setData","test",
>  function(this,fcn,k){
>    this at t <- as.numeric(seq(-k,k))/(2*k+1)
>    this at f <- sapply(t,FUN=fcn)
>  }
> )
>
> #-----------------------------------------------------------
> tst <- new("test")
> fcn <- function(u){ sin(2*pi*u) }
> setData(tst,fcn,100)
> tst at t   # it's still empty because of pass by value
>
>
> How can this be handled?
>
>
> Many thanks,
>
> Michael
>
>        [[alternative HTML version deleted]]
>
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> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Applied mathematics, biometrics and process control

tel : +32 9 264 59 87
Joris.Meys at Ugent.be
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