[R] how to write assignment form of function

[Heinz Tuechler]

At 14:49 10.08.2005 +0200, Dimitris Rizopoulos wrote:
>take a look at e.g., get("levels<-.factor"); you should return "x" in 
>your function, i.e.,
>
>y <- x <- factor(c(1,1,NA,2,3,4,4,4,1,2))
>############
>'levels.simple<-' <- function(x, value){
>      attr(x, 'levels') <- value
>      x
> }
>
>levels.simple(y) <- c('a', 'b', 'c', 'd')
>y
>
>
>I hope it helps.
>
>Best,
>Dimitris
>
Dear Dimitris,

Thank you a lot - it helped. Now it works.

Heinz



>----
>Dimitris Rizopoulos
>Ph.D. Student
>Biostatistical Centre
>School of Public Health
>Catholic University of Leuven
>
>Address: Kapucijnenvoer 35, Leuven, Belgium
>Tel: +32/16/336899
>Fax: +32/16/337015
>Web: http://www.med.kuleuven.be/biostat/
>     http://www.student.kuleuven.be/~m0390867/dimitris.htm
>
>
>----- Original Message ----- 
>From: "Heinz Tuechler" <tuechler at gmx.at>
>To: <r-help at stat.math.ethz.ch>
>Sent: Wednesday, August 10, 2005 2:24 PM
>Subject: [R] how to write assignment form of function
>
>
>Dear All,
>
>where can I find information about how to write an assigment form of a
>function?
>For curiosity I tried to write a different form of the 
>levels()-function,
>since the original method for factor deletes all other attributes of a 
>factor.
>Of course, the simple method would be to use instead of levels(x) <-
>newlevels, attr(x, 'levels') <- newlevels.
>
>I tried the following:
>## example
>x <- factor(c(1,1,NA,2,3,4,4,4,1,2)); y <- x
>attr(x, 'levels') <- c('a', 'b', 'c', 'd')     # does what I want
>x
> [1] a    a    <NA> b    c    d    d    d    a    b
>Levels: a b c d
>
>'levels.simple<-' <- function (x, value)
> {
>      attr(x, 'levels') <- value
> }
>
>levels.simple(y) <- c('a', 'b', 'c', 'd')     # does not what I want
>y
>[1] "a" "b" "c" "d"
>
>Thanks,
>Heinz Tüchler
>
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