[R] setAs vs setIs

From: Christophe Genolini <cgenolin_at_u-paris10.fr>
Date: Mon, 17 Mar 2008 01:12:51 +0100


Hi the list

I am fighting with the twins setAs and setIs...

Here are some questions and comments (comments to myself but that migth be wrong, it is why I am posting them)
1. Very surprising : using setIs define 'is', 'as<-' but not 'as' ??? 2. Using setAs define 'as', 'as<-' but not 'is'... What surprise me is that as<- can be define by both. I would have thing that setis is for 'is', setAs is for 'as' and 'as<-'... Since it is not the case, is there a possibility to set with only one function 'as', 'is' and 'as<-'

Last point, I get a warning using setAs. I did not manage to find the name of the variable it want me to use...

### Data

setClass("B",representation(b="numeric"))
setClass("C",representation(c="numeric"))
setClass("D",representation(d="numeric"))
b <- new("B",b=3)
c <- new("C",c=4)
d <- new("D",d=5)

### using setIs

setIs("C","B",

    test=function(object){return(object_at_c>0)},     replace=function(from,values){

        from_at_c <- values_at_b^3
        return(from)

    }

)
is(c,"B")             #Ok
as(c,"B")             #not ok
as(c,"B") <- b        #ok (!)

### using setAs

setAs("D","B",

    function(from,to){to<-new("B",b=from_at_d);return(to)},     replace=function(from,values){

        from_at_d<-values_at_b^2;
        return(from)

    }
)
is(d,"B")             # not ok
as(d,"B")             # ok
as(d,"B")<-b          # ok


Thanks

Christophe



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