[R] Building packages in R - 'private' functions

[Joerg van den Hoff]

Dan Rabosky wrote:
> Hello.
> 
> I am creating an R package that I'd like to submit to CRAN (OS Windows 
> XP).  How do I distinguish among 'public' functions, e.g., those that are 
> intended to be called by users of the package and for which I am providing 
> documentation & examples, and 'private' functions, which are used 
> internally by the 'public' functions, but for which I do not wish to 
> provide documentation?  The private functions are all coded in R (nothing 
> in C or Fortran) and are essential to the operation of several public 
> functions.
> 
> I have been unable to find any documentation on this in the 'writing r 
> extensions' manual', on previous posts to R-help, or through any other 
> source.  One possibility is to include the source code for the 'private' 
> functions within the public functions.  However, since multiple public 
> functions utilize the same core set of 'private' functions, this seems 
> unwieldy and redundant at best.
> 
> If I simply include the source for the 'private' functions in the "R" 
> directory (without corresponding *.Rd and *.html documentation in /man), 
> then check the package with "R CMD check', it does appear to process the 
> private functions (and successfully builds with R CMD build).  However, I 
> do receive a warning for including undocumented code objects.  Is this the 
> recommended approach and/or is there a better way to do this?  One 
> potential problem with this approach is that - should an error occur within 
> a private function, it may be very difficult for the user to decipher the 
> nature of the problem.
> 
> Any suggestions will be greatly appreciated.
> ~Dan Rabosky
> 
> 
> 
> Dan Rabosky
> Department of Ecology and Evolutionary Biology
> 237 Corson Hall
> Cornell University
> Ithaca, NY14853-2701 USA
> DLR32 at cornell.edu
> web: http://www.birds.cornell.edu/evb/Graduates_Dan.htm
> 
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it's in the 'extensions' manual, including an example I believe:

1.
create a file `NAMESPACE' in the package top level dir (beside `R' and 
`man') containing the single line

exportPattern("^[^\\.]")

2.
name all private functions with a leading `.' (more precisely: all 
functions starting with a `.' are private in this setting).


of course, you can modify the pattern to suit another naming convention.

joerg