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.

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.

Thanks,

Jay Emerson
Michael Kane


-- 
John W. Emerson (Jay)
Assistant Professor of Statistics
Director of Graduate Studies
Department of Statistics
Yale University
http://www.stat.yale.edu/~jay

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