[R] How to write a new "top-level" Trellis/lattice function?

[Marc Paterno]

Hello,

I am trying to write a new "top level" Trellis/lattice function.
By "top-level", I mean a function like 'xyplot', 'histogram',
'bwplot', etc.
These functions all call 'trellis.skeleton', which I am unable to
call;
an attempt to invoke the function that does so yields the error
message:

-----
Error in do.call("trellis.skeleton", c(list(cond = cond, aspect =
aspect,  : 
        couldn't find function "trellis.skeleton"
-----

It seems that 'trellis.skeleton' is an internal (to lattice) function.
Is this correct, and if so, what is the recommended way to develop a
new
top-level Trellis/lattice function?

best regards,
Marc

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Dr. Marc Paterno
Fermi National Accelerator Laboratory