On 18.03.2012 16:08, Patrick Giraudoux wrote:
Le 18/03/2012 14:57, Uwe Ligges a écrit :
On 18.03.2012 11:21, Patrick Giraudoux wrote:
Hi,
I am working at adding namespace to my packages, carefully following the
doc "Writing R extensions" and some threads on the web. However I cannot
find clear explanation about how to best deal with the import or
importFrom functions in the name space. To make it short:
To declare dependencies in the description file either after Depends:
(packages including functions that are called from a package function)
or after Suggests: (packages that are called eg from the doucmentation
examples), works well. In this case one does not need to declare import
in the namespace file.
However, declaring dependencies sometimes for using only one function in
a given package looks a bit over the top, and I though I could use
importFrom in the namespace to deal with that. So removing the
corresponding declaration in Depends (description file) and declaring
eg importFrom(splancs, inout) in the namespace always led to:
* checking package dependencies ... ERROR
Namespace dependency not required: 'splancs'
Same thing with import(sp). I have the same trouble if I do not remove
the declarations in Depends.
So, I can hardly follow the meaning of the "Writing R extension" doc:
Packages implicitly import the base namespace. Variables exported from
other packages with namespaces need to be imported explicitly using the
directives |import| and |importFrom|. The |import| directive imports all
exported variables from the specified package(s). Thus the directives
import(foo, bar)
specifies that all exported variables in the packages *foo* and *bar*
are to be imported. If only some of the exported variables from a
package are needed, then they can be imported using |importFrom|. The
directive
importFrom(foo, f, g)
specifies that the exported variables |f| and |g| of the package *foo*
are to be imported.
Can anybody tell us the conditions for which import and importFrom
commands should be used in the NAMESPACE rather than in the Depends and
Suggests declarations of the description file, and the conditions of
their applicability (without error message... eg with a working
example) ?
If you import from another namespace (which is the recommended way
rather than just relying on search order), do not forget to declare it
as "Imports" in your DESCRIPTION file. Your package depends on the
other one: It could not be loaded without having the other one
installed now.
Uwe Ligges
OK. got it (more or less).
With this in the description file:
Depends: boot (>= 1.3-4), nlme(>= 3.1-64), rgdal (>= 0.7-8), sp (>=
0.9-97), spdep (>= 0.5-43), splancs (>= 2.01-31)
importFrom(splancs, inout) is accepted in the NAMESPACE file and I have
no error message with rcmd check.
Irr works also with:
Depends: boot (>= 1.3-4), nlme(>= 3.1-64), rgdal (>= 0.7-8), sp (>=
0.9-97), spdep (>= 0.5-43)
Imports: splancs (>= 2.01-31)
Practically, I a am safe (thanks a lot), but I am however still hungry
to learn a bit more. I hardly understand what R does when reading the
suggests and imports in the DESCRIPTION file compared to what it does
reading the NAMESPACE (my mistake was to believe that one was a
substitute for the other). From a practical point of view, why is it
important to use import or importFrom in the NAMESPACE when everything
looks like working well when declarations are done in the DESCRIPTION
file only (eg in depends or imports)? It is not crystal clear to me even
reading carefully "Writing R extension". DESCRIPTION file is used to get
the "list of packages that will be attached (...) before the current
package" (indeed, now, I no longer needs to use 'require' within my
package functions). In simple words, what may add the NAMESPACE to that ?
Apologize to be so poorly aware (= so much stupid) about the role of
each of those declaration spaces.
Please read some literature about NAMESPACES, e.g. documentation in
Writing R Extensions plus Luke Tierney's articles in R News.
A NAMESPACE import imports functionality of another namespace into your
own namespace and hence avoids problems caused by name clashes.
The DESCRIPTION file is required to derive dependency structure of
packages, i.e. derive which package has to be *installed* first etc.
Uwe Ligges
Best,
Patrick
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