[R-pkg-devel] Calls not declared

Ah, so as long as you don't need to call a normal function to make use of the returned object you don't need Depends. But in this example, the user would then need to call library(ggplot2) in order to, say, change an axis title.

A bit more subtle than I thought.

On March 11, 2019 10:07:12 AM PDT, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:

On 11/03/2019 11:32 a.m., Jeff Newmiller wrote:

I did not see any mention of the distinction between Depends and

Imports in the DESCRIPTION file... which is always a risk when
duplicating existing documentation in an email. Imports is preferred
because the user does not have to put definitions only needed inside
your package into their public search path (easier to make
under-the-hood changes to the package implementation), but Depends is
better when they cannot make use of your package without those
definitions (e.g. you return a ggplot object from one of your
functions).

You don't need Depends to be able to handle ggplot2 objects. You'll get

the methods when the package is loaded, so they'll print fine without
having ggplot2 on the search list.

There are very few cases nowadays where it makes sense to use Depends.

Duncan Murdoch

So do keep reading the documentation... email is just a kickstart.

On March 11, 2019 8:19:33 AM PDT, Duncan Murdoch

<murdoch.duncan at gmail.com> wrote:

On 11/03/2019 9:53 a.m., Elias Carvalho wrote:

I am developing my first package and found these errors when

checking

it.

Any help?


* checking dependencies in R code ... WARNING
'library' or 'require' calls not declared from:
     ?qgraph? ?semPlot? ?sna? ?xlsx?

Without seeing your package I might be wrong, but I believe this

says

that you have something like

library(qgraph)

somewhere in your R code, without listing

Depends: qgraph

in your DESCRIPTION file.

HOWEVER, fixing this warning will lead to a different one, because
that's not the recommended way to do things now.  There are two
possibilities:

1.  Your package is useless without the dependency.

In this case, you should put

Imports:  qgraph, ...

in the DESCRIPTION file (where ... lists the other packages with the
same status), and list the functions in those packages in your
NAMESPACE
file, using

importFrom(qgraph, ...)

etc.  (If you use Roxygen, you use comments in the source to get it

to

put this into your NAMESPACE file.)

2.  Your package works without the dependency, but you may want to
issue
errors or warnings if it is missing.

Then you should put

Suggests:  qgraph, ...

in the DESCRIPTION file, and to use a function from it, use

something

like

if (requireNamespace("qgraph")) {
    qgraph::foo(...)
} else
    warning("qgraph is not available.")

Duncan Murdoch