R devel - Feb 2015 - alternatives to do.call() when namespace is attached but not loaded?

Dear R-devel

I have a function in a package that essentially provides a wrapper for a 
group of functions in another Suggested package (it sets appropriate 
defaults for the context, transforms output, etc).  I've implemented 
this by verifying that the package was loaded with

require(sna)

and then

do.call(snaFunName, args = args)


The rDevel check is requesting that I use  requireNamespace(sna) instead 
of directly loading the SNA package. This seems reasonable, except that 
I have yet to figure out a way to use do.call to call the function when 
the namespace is attached but package is not loaded. 
do.call("sna::funName",..) doesn't seem to work.

1) Can do.call() call functions that are only namespace attached? Is 
there better way to accomplish this without do.call()? For example, 
should I use getAnywhere('funName') ('tho this doesn't seem to
permit
restricting search to a specific namespace..)

2) Is this an appropriate of require() instead of requireNamespace() to 
ensure that the Suggested package is loaded and attached? Can I ignore 
the check warning?

best,
  -skye

First, a clarification of terminology: a package can be loaded and
attached, or loaded and not attached. It can't be attached and not loaded.

To get the function from a package by name, you could do something like:
  getExportedValue("sna", snaFunName)

where snaFunName is a string containing the name of the function.

-Winston



On Tue, Feb 24, 2015 at 12:29 PM, Skye Bender-deMoll <skyebend at
skyeome.net>
wrote:
> Dear R-devel
>
> I have a function in a package that essentially provides a wrapper for a
> group of functions in another Suggested package (it sets appropriate
> defaults for the context, transforms output, etc).  I've implemented
this
> by verifying that the package was loaded with
>
> require(sna)
>
> and then
>
> do.call(snaFunName, args = args)
>
>
> The rDevel check is requesting that I use  requireNamespace(sna) instead
> of directly loading the SNA package. This seems reasonable, except that I
> have yet to figure out a way to use do.call to call the function when the
> namespace is attached but package is not loaded.
do.call("sna::funName",..)
> doesn't seem to work.
>
> 1) Can do.call() call functions that are only namespace attached? Is there
> better way to accomplish this without do.call()? For example, should I use
> getAnywhere('funName') ('tho this doesn't seem to permit
restricting search
> to a specific namespace..)
>
> 2) Is this an appropriate of require() instead of requireNamespace() to
> ensure that the Suggested package is loaded and attached? Can I ignore the
> check warning?
>
> best,
>  -skye
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
	[[alternative HTML version deleted]]

do.call(sna::snaFunName, args = args)

?

Hadley

On Tue, Feb 24, 2015 at 1:29 PM, Skye Bender-deMoll
<skyebend at skyeome.net> wrote:
> Dear R-devel
>
> I have a function in a package that essentially provides a wrapper for a
> group of functions in another Suggested package (it sets appropriate
> defaults for the context, transforms output, etc).  I've implemented
this by
> verifying that the package was loaded with
>
> require(sna)
>
> and then
>
> do.call(snaFunName, args = args)
>
>
> The rDevel check is requesting that I use  requireNamespace(sna) instead of
> directly loading the SNA package. This seems reasonable, except that I have
> yet to figure out a way to use do.call to call the function when the
> namespace is attached but package is not loaded.
do.call("sna::funName",..)
> doesn't seem to work.
>
> 1) Can do.call() call functions that are only namespace attached? Is there
> better way to accomplish this without do.call()? For example, should I use
> getAnywhere('funName') ('tho this doesn't seem to permit
restricting search
> to a specific namespace..)
>
> 2) Is this an appropriate of require() instead of requireNamespace() to
> ensure that the Suggested package is loaded and attached? Can I ignore the
> check warning?
>
> best,
>  -skye
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


-- 
http://had.co.nz/

> On 24 Feb 2015, at 19:53 , Hadley Wickham <h.wickham at gmail.com>
wrote:
> 
> do.call(sna::snaFunName, args = args)
> 
> ?
> 
I was about to suggest something similar. The key is that the first arg to
do.call is not necessarily a text string; it can be the actual function object.
So something along the lines of

name <- as.name("snaFunName")
f <- eval(bquote(sna::.(name)))
do.call(f, args)

should work too. 
> Hadley
> 
> On Tue, Feb 24, 2015 at 1:29 PM, Skye Bender-deMoll
> <skyebend at skyeome.net> wrote:
>> Dear R-devel
>> 
>> I have a function in a package that essentially provides a wrapper for
a
>> group of functions in another Suggested package (it sets appropriate
>> defaults for the context, transforms output, etc).  I've
implemented this by
>> verifying that the package was loaded with
>> 
>> require(sna)
>> 
>> and then
>> 
>> do.call(snaFunName, args = args)
>> 
>> 
>> The rDevel check is requesting that I use  requireNamespace(sna)
instead of
>> directly loading the SNA package. This seems reasonable, except that I
have
>> yet to figure out a way to use do.call to call the function when the
>> namespace is attached but package is not loaded.
do.call("sna::funName",..)
>> doesn't seem to work.
>> 
>> 1) Can do.call() call functions that are only namespace attached? Is
there
>> better way to accomplish this without do.call()? For example, should I
use
>> getAnywhere('funName') ('tho this doesn't seem to
permit restricting search
>> to a specific namespace..)
>> 
>> 2) Is this an appropriate of require() instead of requireNamespace() to
>> ensure that the Suggested package is loaded and attached? Can I ignore
the
>> check warning?
>> 
>> best,
>> -skye
>> 
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
> 
> 
> -- 
> http://had.co.nz/
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com