>>>>> Lenth, Russell V
>>>>> on Thu, 24 May 2018 23:14:42 +0000 writes:
> Package developers, I am trying to severely cut down on
> the number of dependencies of my package emmeans. It is
> now 48, which is quite a few (but that is down from over
> 100 in the preceding version, where I made the unwise
> choice of including a particularly greedy package in
> Imports). I hate to force users to install dozens of
> packages that they don't really need or want, but it seems
> very hard to avoid.
> Case in point: emmeans provides additional methods for
> 'cld' and 'glht' from the multcomp package. Accordingly, I
> import their generics, and register my additional
> methods. But because I import the generics, I must list
> multcomp in Imports, and that results in the addition of
> 16 required packages, some of which I never use. More
> important, I believe that NONE of those 16 packages are
> required for the correct functioning of my courtesy
> methods. The only things I really need are the generics.
There must be a mistake here -- I think in your perception:
'multcomp' does *not* have excessive dependencies (though I'd
say one too much):
> tools::package_dependencies("multcomp")
$multcomp
[1] "stats" "graphics" "mvtnorm" "survival" "TH.data" "sandwich"
[7] "codetools"
> tools::package_dependencies("multcomp", recursive=TRUE)
$multcomp
[1] "stats" "graphics" "mvtnorm" "survival" "TH.data" "sandwich"
[7] "codetools" "methods" "utils" "zoo" "Matrix" "splines"
[13] "MASS" "grDevices" "grid" "lattice"
>
Apart from "base + recommended" packages (which *everyone* has installed),
these are just 4 packages:
mvtnorm
TH.data
sandwich
zoo
where mvtnorm, sandwich, and zoo really are among the
(formally undefined) recommended-level-2 R packages... so I do
wonder if you really had needed to install.
The 'TH.data' { TH <==> maintainer("multcomp") } package I
think should not be in the strict dependencies of 'multcomp' but
rather in its "Suggests".... something I'd say must be true for
all data packages:
The whole idea of data packages is that they should be needed
for interesting help page examples, vignettes, maybe even tests,
but not for package functionality.
In sum: I'd strongly advise to not change from keeping multcomp
among your imports.
Martin Maechler
ETH Zurich
> On the flip side, emmeans defines some generics of its own
> that I invite other package developers to extend so that
> emmeans supports their models. If those packages import
> emmeans, there is an overhead of 48 dependencies; again,
> most of these are packages that are not needed at all for
> those packages' methods to work. I don't like being
> responsible for that.
> I believe this is a very common problem, not just with my
> own packages. It's one thing to extend a base method like
> 'print'; but extending methods in contributed packages
> creates these dependency explosions. I have hundreds of
> packages installed on my system - a couple dozen I care
> about, another few dozen that seem fairly desirable, and a
> couple hundred that I don't even know what they're for,
> other than that things will break if I uninstall them.
> I do know of a couple ways to reduce these dependencies in
> the case of my multcomp dependencies:
> 1. I could simply export my S3 methods for cld and glht as
> functions, rather than registering them as S3 methods.
> Then I could move multcomp to Suggests. The downside is
> that it clutters the namespace for emmeans.
> 2. I could define the generics for cld and glht in my own
> package, and export them; and move multcomp to Suggests.
> Again, it clutters the namespace, and creates warning
> messages about (if not real issues with) masking.
> Probably (1) is better than (2), but is it better than
> what I do now? Is there something else that I (and
> probably a whole lot of other people) don't know?
> I wish there were an ImportGenerics or an
> ImportWithoutDependencies or some such field possible in
> DESCRIPTION.
> I appreciate any suggestions. Thanks
> Russ
> --
> Russell V. Lenth - Professor Emeritus Department of
> Statistics and Actuarial Science The University of Iowa
> - Iowa City, IA 52242 USA Voice (319)335-0712 -
> FAX (319)335-3017 russell-le...@uiowa.edu -
> http://www.stat.uiowa.edu/~rlenth/
> ______________________________________________
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