[R] Controlling line-join style in Lattice

[Morgan, Andrew Parker]

R users,

I am creating a series of scatterplots with Lattice's xyplot().  Some of the plotting symbols are squares with thick borders.  The corners of the squares are rounded by default; I would like them to be square.  In base graphics this is easily done with par(ljoin = "mitre"), and in grid graphics with gpar(linejoin = "mitre").  Is there an analogous parameter in Lattice?  Passing ljoin as an argument to xyplot() or panel functions doesn't seem to work, and I can't find anything promising in lattice.par.get().

Thanks,
Andrew Morgan
Department of Genetics
University of North Carolina - Chapel Hill