R help - Mar 2009 - Using a NAMESPACE or the Imports field in DESCRIPTION?

Hello list,

I am writing a package which builds on a function ("foo") of another 
package. I only need that particular function. What is the state of 
the art to do this? Do I need a NAMESPACE file in my package? 
Currently I still don't have one. Or can I do this with the Imports 
field in my DESCRIPTION file? Reading chapter 1 of the "Writing R 
Extensions" manual I do not completely understand for what situations 
these two alternatives are intended for. The manual says that with 
the Imports field of DESCRIPTION I can "import the name space" of 
another package. What does that mean? What are the differences 
between the two alternatives? Are there consequences for how I can 
access function "foo" within the code of my package?

Thanks for some clarifications and recommendations!

Wolfgang Koller

Hi Wolfgang --

Wolfgang Koller wrote:
> Hello list,
> 
> I am writing a package which builds on a function ("foo") of
another
> package. I only need that particular function. What is the state of the 
> art to do this? Do I need a NAMESPACE file in my package? Currently I 
> still don't have one. Or can I do this with the Imports field in my 
> DESCRIPTION file? Reading chapter 1 of the "Writing R Extensions"
manual
> I do not completely understand for what situations these two 
> alternatives are intended for. The manual says that with the Imports 
> field of DESCRIPTION I can "import the name space" of another
package.
> What does that mean? What are the differences between the two 
> alternatives? Are there consequences for how I can access function
"foo"
> within the code of my package?
It sounds like you want to add Imports: OtherPackage to DESCRIPTION, and

importFrom(OtherPackage, foo)

in you NAMESPACE file, in addition perhaps to

export(foo)

if you'd like users of your package to access foo. Using a NAMESPACE can 
be very beneficial, especially as your software grows in complexity -- 
it ensures ready access to the symbols you want (foo, in this case) 
without relying on the structure of the user search path. I don't think 
adding Imports to DESCRIPTION and adding a NAMESPACE should really be 
viewed as 'alternatives' -- add a NAMESPACE, and many of the packages 
that you had previously listed in Depends: likely belong more 
appropriately in Imports.

Martin
> Thanks for some clarifications and recommendations!
> 
> Wolfgang Koller
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

-- 
Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N.
PO Box 19024 Seattle, WA 98109

Location: Arnold Building M2 B169
Phone: (206) 667-2793