R devel - Jan 2013 - Declaring/importing non-exported functions [car] in another package

A new function in my heplots package wants to use a non-exported utility 
function in the car package,
df.terms, but this depends on other non-exported functions.
 From the Writing R extensions manual, I thought I could do this via (in 
my NAMESPACE)

importFrom(car, car:::df.terms, car:::df.terms.default, car:::is.aliased)

but I get:
** preparing package for lazy loading
Error : objects 'car:::df.terms', 'car:::df.terms.default', 
'car:::is.aliased' are not exported by 'namespace:car'
ERROR: lazy loading failed for package 'heplots'

\S 1.6.1 of the manual says regarding importFrom():
Using |foo:::f| instead of |foo::f| allows access to unexported objects. 
This is generally not recommended, as the semantics of unexported 
objects may be changed by the package author in routine maintenance.

Questions:
1.  Why doesn't this work?
2.  Is my only alternative to copy these functions to my package, also 
unexported?

thx,
-Michael

-- 
Michael Friendly     Email: friendly AT yorku DOT ca
Professor, Psychology Dept. & Chair, Quantitative Methods
York University      Voice: 416 736-2100 x66249 Fax: 416 736-5814
4700 Keele Street    Web:   http://www.datavis.ca
Toronto, ONT  M3J 1P3 CANADA


	[[alternative HTML version deleted]]

On 13-01-16 11:25 AM, Michael Friendly wrote:
> A new function in my heplots package wants to use a non-exported utility
> function in the car package,
> df.terms, but this depends on other non-exported functions.
>   From the Writing R extensions manual, I thought I could do this via (in
> my NAMESPACE)
>
> importFrom(car, car:::df.terms, car:::df.terms.default, car:::is.aliased)
>
> but I get:
> ** preparing package for lazy loading
> Error : objects 'car:::df.terms', 'car:::df.terms.default',
> 'car:::is.aliased' are not exported by 'namespace:car'
> ERROR: lazy loading failed for package 'heplots'
>
> \S 1.6.1 of the manual says regarding importFrom():
> Using |foo:::f| instead of |foo::f| allows access to unexported objects.
> This is generally not recommended, as the semantics of unexported
> objects may be changed by the package author in routine maintenance.
>
> Questions:
> 1.  Why doesn't this work?
I think you misread the manual.  It is talking about ways to access 
functions other than by using importFrom.  You can use car:::df.terms in 
your functions.
> 2.  Is my only alternative to copy these functions to my package, also
> unexported?
Using car:::df.terms explicitly is another option.

Another possibility is for the car maintainer (John Fox) to export that 
function from car.

Duncan Murdoch