[Rd] Depending/Importing data only packages

Paul Gilbert pgilbert902 at gmail.com
Sat Dec 7 19:35:33 CET 2013

On 13-12-07 12:19 PM, Gábor Csárdi wrote:
> I don't know about this particular case, but in general it makes sense
> to rely on a data package. E.g. I am creating a package that does
> Bayesian inference for a particular problem, potentially relying on
> prior knowledge. I think it makes sense to put the data that is used
> to calculate the prior into another package, because it will be larger
> than the code, and it does not change that often.
> Gabor
> On Sat, Dec 7, 2013 at 11:51 AM, Paul Gilbert <pgilbert902 at gmail.com> wrote:
>> Would "Suggests" not work in this situation? I don't understand why you
>> would need Depends. In what sense do you rely on the data only package?

HW> Because I want someone who downloads the package to be able to run
HW> the examples without having to take additional action.
HW> Hadley

I went through this myself, including thinking it was a nuisance for 
users to need to attach other packages to run examples. In the end I 
decided it is not so bad to be explicit about what package the example 
data comes from, so illustrate it in the examples. Users may not always 
want this data, and other packages that build on yours probably do not 
want it.

Even in the Bayesian inference case pointed out by Gábor, I am not 
convinced. It means the prior knowledge base cannot be exchanged for 
another one. The package would be more general if it allowed the 
possibility of attaching a different database of prior information. But 
this is clearly a more important case, since the code probably does not 
work without some database. (There are a few other situations where 
something like "RequireOneOf:" would be useful.)


>> Paul
>> On 13-12-06 04:20 PM, Hadley Wickham wrote:
>>> Hi all,
>>> What should you do when you rely on a data only package. If you just
>>> "Depend" on it, you get the following from R CMD check:
>>> Package in Depends field not imported from: 'hflights'
>>>     These packages needs to imported from for the case when
>>>     this namespace is loaded but not attached.
>>> But there's nothing in the namespace to import, so adding it to
>>> imports doesn't seem like the right answer.  Is that just a spurious
>>> note?
>>> Hadley
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