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
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Martin Morgan
Computational Biology / Fred Hutchinson Cancer Research Center
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