[R] detach

[Gabor Grothendieck]

Looks like one can do the following.  Don't know if it would cause
problems elsewhere.  Note that after removing as.Date.numeric
from the S3 Methods Table as.Date.numeric was no longer dispatched.

> as.Date(1)
Error in as.Date.default(1) : do not know how to convert '1' to class "Date"
> library(zoo)
> as.Date(1)
[1] "1970-01-02"
> unloadNamespace("zoo")
<environment: namespace:zoo>
> rm(as.Date.numeric, envir = .__S3MethodsTable__.)
> as.Date(1)
Error in as.Date.default(1) : do not know how to convert '1' to class "Date"

On 7/12/06, Prof Brian Ripley <ripley at stats.ox.ac.uk> wrote:
> On Wed, 12 Jul 2006, Martyn Plummer wrote:
>
> > My guess is that even though the zoo namespace is unloaded. The S3
> > method as.Date.numeric is still registered, and the name space will be
> > reloaded whenever it is dispatched.
> > > library(zoo)
> > > loadedNamespaces()
> > [1] "base"      "graphics"  "grDevices" "methods"   "stats"     "utils"
> > [7] "zoo"
> > > unloadNamespace("zoo")
> > <environment: namespace:zoo>
> > > loadedNamespaces() #Gone
> > [1] "base"      "graphics"  "grDevices" "methods"   "stats"     "utils"
> > > as.Date(1)
> > [1] "1970-01-02"
> > > loadedNamespaces() #Back again!
> > [1] "base"      "graphics"  "grDevices" "methods"   "stats"     "utils"
> > [7] "zoo"
> >
> > So the question is whether there is a way to unregister an S3 method, so
> > that you can restore the method dispatching behaviour prior to the
> > package being loaded. I don't know the answer, but I'm guessing it's no.
>
> It is no.  Namespaces don't work that way: one would have to keep a stack
> of past registered methods to be able to back out a registered method.
>
> --
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>