[Rd] Recommended way to call/import functions from a Suggested package

[Simon Urbanek]

On Feb 26, 2013, at 5:47 PM, Hervé Pagès wrote:

> Hi,
> 
> So MASS::huber(1:10) seems to do the job i.e. (1) loads the MASS
> package (if it's installed), (2) does not pollute the search path,
> (3) no 'R CMD check' warning if MASS is listed in Suggests,
> and (4) descent error message if MASS is not installed:
> 
>  > MASS::huber(1:10)
>  Error in loadNamespace(name) : there is no package called ‘MASS’
> 

But (4) is a problem - it may not fail without MASS since it is only suggested, that's why you need the try() ... The whole thread (which you omitted) was started because the usual if(require(...)) { .. } has an unwanted side-effect which the requestor did not want so the question was what does the job and that got settled before you joined in ...

Cheers,
S




> So is this recommendable or are there good reasons for stating in
> the manual that "this approach is usually not recommended"? (In which
> case it would be good to know what the recommended way is.)
> 
> Thanks,
> H.
> 
> 
> On 02/25/2013 02:56 PM, Hadley Wickham wrote:
>>> loadNamespaces loads but does not attach the package. Suggests: is enough to
>>> quieten the warning with
>>> 
>>> ~/tmp$ R --version
>>> R Under development (unstable) (2013-02-21 r62017) -- "Unsuffered
>>> Consequences"
>>> 
>>> This is consistent with RShowDoc("R-exts") section 1.1.1
>>> 
>>>   Namespaces accessed by the ‘::’ and ‘:::’ operators must be listed here,
>>> or in ‘Suggests’ or ‘Enhances’ (see below).
>> 
>> I guess that's changed since I last tried it.  (My reproducible
>> example forgot to include MASS in the Suggests :/ )
>> 
>> Thanks!
>> 
>> Hadley
>> 
> 
> -- 
> Hervé Pagès
> 
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M1-B514
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> 
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> 
>