[R] S4 : setGeneric for classical methods

[Martin Maechler]

>>>>> "CG" == Christophe Genolini <cgenolin at u-paris10.fr>
>>>>>     on Tue, 22 Jul 2008 19:04:37 +0200 writes:

    CG> Prof Brian Ripley <ripley at stats.ox.ac.uk> a écrit :
    >> On Tue, 22 Jul 2008, cgenolin at u-paris10.fr wrote:
    >> 
    >>> Hi the list (well, half of the list, only the one who
    >>> are not on holidays...)
    >>> 
    >>> I am trying to make an S4 package. When I run it on a
    >>> console, everything seems ok. When I run R CMD check, I
    >>> got an error --- 8<
    >>> ----------------------
    >>> Error in setMethod("plot", "ClassX", function(x, y) { :
    >>> no existing definition for function "plot" --- 8<
    >>> ----------------------
    >>> 
    >>> If I add
    >>> setGeneric("plot",function(x,y,...){standardGeneric("plot")})
    >>> in my code, then everything is OK.
    >>> 
    >>> This is a surprise for me since I taught that we do not
    >>> need to redefine as generic the function that are
    >>> already generic, like "plot". Am I wrong ?
    >> 
    >> Yes. And do read the error message.  It says
    >> 
    >> no existing definition for function "plot"
    >> 
    >> so this is not if the function is S3 or S4 generic, but
    >> that no such function is visible.
    >> 
    >> Looks like you forgot to declare a dependence on (or
    >> import) package graphics.

    CG> I would have forgot if I knew that I have to declare
    CG> such a dependence...  Do we have to declare all the
    CG> depence to all the package ? To base ? To stats ? 

not to base, but to all other packages (since R can be loaded
without any packages but base).

    CG> I thaught that the package that are include in R when we
    CG> start it had not to be include.

You thought wrongly, and all our documentation mentions that you
need to use 'Depends:' correctly (and  'Imports(..)' in
NAMESPACE if you make use of one).

{and please strongly note the correct spelling of "thought" !}

Martin