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NAMESPACE choices for exporting S4 methods
3 messages · Jay Emerson, Brian Ripley
On Sat, 8 Dec 2007, Jay Emerson wrote:
We are building a package, and want to create S4 methods for both head and mean for our own BigMatrix class. Following the recommendation in "Writing R Extensions" we use exportMethods instead of export in NAMESPACE (this is described as being "clearer"). This works for head, but not for mean. Obviously we importFrom(utils, head), but don't need to do this for mean, which is imported automatically from base.
And what is the error message?
If we export(mean) rather than exportMethods(mean), it works as intended. A similar problem arises for a new generic function and an associated method, colmean, where the use of exportMethods(colmean) fails, but export(colmean) succeeds. We can build and use the package by using export instead of exportMethods, but we suspect that we're missing something that might be important to understand. Any hints or links to something we missed would be appreciated.
I know there are problems if you define a generic and no methods in a package (that is what stats4 does for AIC), but it doesn't sound as if that is what you are doing. (Since the introduction of implicit generics - which may well apply to your mean() - it is possible to define a generic in a package without any methods stored there, not even a default method.) I saw nothing in your description that is different from several other pacakges. Without either the error messages or an example, we are reduced to guessing. Can you make a minimal version available to us to look at?
Brian D. Ripley, ripley at stats.ox.ac.uk Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595
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