[Rd] Incorporating single functions from other packages: rules and regulations?

[Ben Bolker]

Tim Triche, Jr. <tim.triche <at> gmail.com> writes:

>  a n00b question:
> 
> if I call importFrom(IRanges, ranges) in my NAMESPACE file, that works
> great.
> but if  I call
> 
> R> importFrom(IRanges, ranges)
> ## Error: could not find function "importFrom"
> 
> well, that doesn't work great.  The closest thing I can find in base is
> 
> base:::importIntoEnv
> 
> which helpfully informs me that it is one of several
> 
> Internal namespace support functions.  Not intended to be called directly.
> 
> Where's the best place to learn about how namespaces and import/export
> facilities (particularly in R-3.0) are implemented?

   Have you tried the R Extensions manual?  That doesn't quite
answer the "how are they implemented" question, but it should
cover "how should they be used" about as thoroughly as possible.

http://obeautifulcode.com/R/How-R-Searches-And-Finds-Stuff/ may
be useful as well.

 Beyond that, you have to look at the R language manual (if at
has anything) or the source code, I think.

> On Sun, Jan 13, 2013 at 7:05 AM, Dirk Eddelbuettel <edd <at> debian.org> wrote:
> 
> >
> > On 13 January 2013 at 11:16, Johannes Graumann wrote:
> > | In a little pkg I'm developing I am in need of the functionality
> > provided by
> > | plotrix::listDepth.
> > |
> > | I am loath of having the depend on and import the whole package just for
> > | that purpose.
> >
> > Step back and realize that your total R installation (including all
> > packages)
> > is already much bigger than the single package. And derives value from all
> > those packages.
> >
> > So I would use importForm(plotrix, listDepth) in my package's NAMESPACE,
> > and
> > add the Imports: in the DESCRIPTION.
> >
> > IMHO that is the right way to do it rather than creating _stale_ and (even
> > worse) _disconnected_ copies which will never receive updates or fixes from
> > the _original author_ of that code.
> >
> > Dirk

  I agree/sympathize but can also think of cases, if the function is
short/simple enough, that it would actually make sense to copy it.
It's a judgment call, I think.

Most R packages are under sufficiently permissive licenses (plotrix is
'GPL >=2') that copying is allowed, although it would be courteous to
inform/ask permission from the author(s).

  Ben Bolker