[R] Filled triangles in lattice graphics?

[Hans Gardfjell]

Dear R users,

I can get a filled triangle pointing upwards by specifying pch=17 in 
xyplot or lpoints, but how do I get a filled triangle that points downwards?

In the standard plot function it's possible to use 
plot(x,y,pch=25,bg="black"), but bg= doesn't seem to work with lattice 
and lpoints.

Thanks,

Hans Gardfjell
Ecology and Environmental Science
Umeå University, Sweden