[Rd] Loading of namespace on load of .Rdata (was strange behaviour of load)

[Roger Peng]

[R-help removed]

See below.

Heather Turner wrote:

<snip>
> 
> 1. There is a more general situation where it would be useful to load
> the namespace of a package after loading a saved workspace: when the
> workspace contains objects of a class for which special methods are
> required. E.g. if 'fm' from the example above were saved in a
> workspace, the namespace of MASS would not be loaded when the
> workspace was loaded into R. Thus unless MASS was loaded by the user,
> default methods would be used by summary(), print() etc rather than
> the specialised methods for objects of class "loglm".
> 
> Of course the user should quickly realise this, but there may be
> cases where the default method gives a convincing but incorrect or
> unhelpful result. An alternative would be to add an attribute to
> objects of class "loglm" (say), e.g. attr(loglmObject,
> ".Environment") <- environment(MASS) so that the namespace would
> automatically be loaded when it is required. [In fact alternatives
> such as environment(loglmObject) <- environment(MASS) or
> loglmObject$anyoldthing <- environment(MASS) would work just as well,
> but perhaps the first suggestion is neatest.].
> 
> What do others think of this idea? Should it (or an equivalent idea)
> be encouraged amongst package writers?

If I understand you correctly here, what you are talking about works 
with S4 classes.  For example, if I load an object 'x' (say, from a 
saved workspace) of class "foo" and it has a 'show()' method in package 
"bar", then

show(x)

will automatically load package "bar".  I this is accomplished because 
there is a "package" attribute that is part of the class of the object.

It's true, what you're talking about does not exist in S3, but since it 
does in S4, I'm not sure it's worth enhancing the older system.

> 
> 2. In the case highlighted by Giovanni, the namespace of ipred was
> loaded, but the package was not. This would be fine, except that the
> packages on which ipred depends *were* loaded. This seems
> inconsistent. I guess as long as there are packages without
> namespaces though, this is the only way to proceed. Perhaps in the
> meantime, package authors should be encouraged to use importFrom()
> rather than import()? Or perhaps where packages do have namespaces,
> only the namespace should be loaded in such a case.
> 
> Heather
> 
> 
>> From: Prof Brian Ripley <ripley at stats.ox.ac.uk> Date: 12 January
>> 2006 08:21:35 GMT To: giovanni parrinello <parrinel at med.unibs.it> 
>> Cc: r-help at stat.math.ethz.ch Subject: Re: [R] Strange behaviour of
>> load
>> 
>> On Wed, 11 Jan 2006, giovanni parrinello wrote:
>> 
>> 
>>> Dear All, simetimes when I load an Rdata I get this message
>>> 
>>> ####### Code:
>>> 
>>> load('bladder1.RData') Carico il pacchetto richiesto: rpart ( Bad
>>> traslastion: Load required package-...) Carico il pacchetto
>>> richiesto: MASS Carico il pacchetto richiesto: mlbench Carico il
>>> pacchetto richiesto: survival Carico il pacchetto richiesto:
>>> splines
>>> 
>>> Carico il pacchetto richiesto: 'survival'
>>> 
>>> 
>>> The following object(s) are masked from package:Hmisc :
>>> 
>>> untangle.specials
>>> 
>>> Carico il pacchetto richiesto: class Carico il pacchetto
>>> richiesto: nnet #########
>>> 
>>> So  I have many unrequired packages loaded. Any idea?
>> 
>> They are required!  My guess is that you have object(s) saved with 
>> environment the namespace of some package, and loading that
>> namespace is pulling these in.  The only CRAN package which
>> requires mlbench appears to be ipred, and that requires all of
>> those except splines, required by survival.
>> 
>> So I believe you have been using ipred and have saved a reference
>> to its namespace.
>> 
>> -- 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
>> 
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> 
> 
> Dr H Turner Research Assistant Dept. of Statistics The University of
> Warwick Coventry CV4 7AL
> 
> Tel: 024 76575870 Url: www.warwick.ac.uk/go/heatherturner
> 
> ______________________________________________ R-devel at r-project.org
> mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
> 

-- 
Roger D. Peng  |  http://www.biostat.jhsph.edu/~rpeng/