R help - Sep 2008 - How is the binding for a super assignment made visible?

The statement Globals <<- list() in the body of a function in a package
was intended to write an empty list to the R workspace to collect results during
the computations of the function.  A package name space has not been specified.

The package appears to function correctly, but

during the R CMD check of the package while "checking R code for possible
problems ... NOTE",

no visible binding for '<<-' assignment to 'Globals' is
displayed.

Can you tell in this case why the binding needs to be visible?  What statement
might do that?  A specific reference in the R manuals would be appreciated.

Bill Morphet
ATK Space Systems, Launch Systems, Nozzle Structural Analysis

On Tue, 2 Sep 2008 morphwj at comcast.net wrote:
> The statement Globals <<- list() in the body of a function in a
package was
> intended to write an empty list to the R workspace to collect results
during
> the computations of the function.  A package name space has not
beenspecified.
>
> The package appears to function correctly, but
>
> during the R CMD check of the package while "checking R code for
possible
> problems ... NOTE",
>
> no visible binding for '<<-' assignment to 'Globals'
is displayed.
>
> Can you tell in this case why the binding needs to be visible?  What
> statement might do that?  A specific reference in the R manuals would be
> appreciated.
The message really parses as "no binding (as far as we can see)" -
it's a request for a binding, not a request for visibility. It's phrased
that way because it is possible to have false positives in this code --
variables that really have been previously defined, but don't look as if
they have.

You are using <<- on a variable that doesn't appear to have been
previously defined in your code.  In fact, as you tell us, it wasn't
previously defined, so the note is correct.  This isn't an error, but is
often a bad idea: the assignment will overwrite any existing variable called
Globals that happens to be in the workspace.

One alternative (since you don't have a namespace) would be to define a
variable
   Globals <- list()
at the top level in your package.  The superassignments would then modify that
variable.

        -thomas



Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle

You could try using an assign statement instead:

assign("Globals", list(), .GlobalEnv)

and see if it complains about that or not.

On Mon, Sep 1, 2008 at 10:01 PM,  <morphwj at comcast.net>
wrote:
> The statement Globals <<- list() in the body of a function in a
package was intended to write an empty list to the R workspace to collect
results during the computations of the function.  A package name space has not
been specified.
>
> The package appears to function correctly, but
>
> during the R CMD check of the package while "checking R code for
possible problems ... NOTE",
>
> no visible binding for '<<-' assignment to 'Globals'
is displayed.
>
> Can you tell in this case why the binding needs to be visible?  What
statement might do that?  A specific reference in the R manuals would be
appreciated.
>
> Bill Morphet
> ATK Space Systems, Launch Systems, Nozzle Structural Analysis
>
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