On Feb 22, 2013, at 6:39 PM, David Winsemius wrote:
>
> On Feb 22, 2013, at 6:13 PM, Hadley Wickham wrote:
>
>> Hi Davor,
>>
>> To the best of my knowledge, there's only one way to use functions
>> from a suggested package: with require:
>>
>> if (require("suggested_package")) {
>> function_from_suggested_package()
>> } else {
>> stop("suggested package not installed")
>> }
>>
>> Unfortunately I don't think there's any way to use a suggested package
>> without polluting the search path.
>
> I've always wondered: How does lattice manage to use grid functions without
> putting them on the search path?
Maybe I am using the wrong terminology, so here is the behavior I'm referring
to:
> sessionInfo()
snipped version an locale ino
attached base packages:
[1] grDevices datasets splines graphics utils stats methods base
other attached packages:
[1] rms_3.6-2 Hmisc_3.10-1 survival_2.37-2 sos_1.3-5 brew_1.0-6
[6] lattice_0.20-10
loaded via a namespace (and not attached):
[1] cluster_1.14.3 grid_2.15.2
Notice that lattice is loaded from my profile
> require(ggplot2)
Loading required package: ggplot2
> sessionInfo()
.... snipped version an locale ino
attached base packages:
[1] grDevices datasets splines graphics utils stats methods base
other attached packages:
[1] ggplot2_0.9.3 rms_3.6-2 Hmisc_3.10-1 survival_2.37-2 sos_1.3-5
[6] brew_1.0-6 lattice_0.20-10
loaded via a namespace (and not attached):
[1] cluster_1.14.3 colorspace_1.2-1 dichromat_2.0-0 digest_0.6.0
[5] grid_2.15.2 gtable_0.1.2 labeling_0.1 MASS_7.3-22
[9] munsell_0.4 plyr_1.8 proto_0.3-10 RColorBrewer_1.0-5
[13] reshape2_1.2.2 scales_0.2.3 stringr_0.6.2
> ?grid.text
No documentation for ‘grid.text’ in specified packages and libraries:
you could try ‘??grid.text’
So at least the help system cannot find a grid function.
> ?grid::grid.text
starting httpd help server ... done
> grid.text
Error: object 'grid.text' not found
Neither can the R interpreter find it. But it's clearly available if you ask
nicely:
> grid::grid.text
function (label, x = unit(0.5, "npc"), y = unit(0.5, "npc"),
just = "centre", hjust = NULL, vjust = NULL, rot = 0, check.overlap =
FALSE,
default.units = "npc", name = NULL, gp = gpar(), draw = TRUE,
vp = NULL)
{
tg <- textGrob(label = label, x = x, y = y, just = just,
hjust = hjust, vjust = vjust, rot = rot, check.overlap = check.overlap,
default.units = default.units, name = name, gp = gp,
vp = vp)
if (draw)
grid.draw(tg)
invisible(tg)
}
<bytecode: 0x11617dd50>
<environment: namespace:grid>
--
David/
>
> --
> David
>>
>> Hadley
>>
>> On Fri, Feb 22, 2013 at 6:26 PM, Davor Cubranic <cubra...@stat.ubc.ca> wrote:
>>> If in my package "Foo" I call a function from another package "Bar" if it's
>>> available, according to R-exts, this sounds like I should include
>>> "Suggests: Bar" in package Foo's description. But the manual is silent on
>>> how to treat Bar's namespace. Should I import it? If so, should this be
>>> conditional or unconditional? There is a thread from 2008 in which Duncan
>>> Murdoch suggests trying conditionally importing a package if it's
>>> installed, with the caveat "If this is allowed"
>>> (http://tolstoy.newcastle.edu.au/R/e5/devel/08/10/0488.html). This appears
>>> to work in current release of R, 2.15.2, but I'm still not clear if it's
>>> officially allowed, much less recommended.
>>>
>>> The manual also says:
>>>
>>>> If a package only needs a few objects from another package it can use a
>>>> fully qualified variable reference in the code instead of a formal import.
>>>> A fully qualified reference to the function f in package foo is of the
>>>> form foo::f. This is slightly less efficient than a formal import and also
>>>> loses the advantage of recording all dependencies in the NAMESPACE file,
>>>> so this approach is usually not recommended. Evaluating foo::f will cause
>>>> package foo to be loaded, but not attached, if it was not loaded
>>>> already—this can be an advantage in delaying the loading of a rarely used
>>>> package.
>>>>
>>>
>>>
>>> Would this be a better solution than importing when calling into a
>>> suggested package?
>>>
>>> Davor
>>>
>>>
>>> [[alternative HTML version deleted]]
>>>
>>>
>>> ______________________________________________
>>> R-devel@r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>
>>
>>
>> --
>> Chief Scientist, RStudio
>> http://had.co.nz/
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
> David Winsemius
> Alameda, CA, USA
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
David Winsemius
Alameda, CA, USA
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