
About a year ago, I noticed that the image() function generated fine 
grid lines
in graphics when using the quartz() device but not x11() and that these
lines could be found in the pdf() generated images when viewed  in some
but not all pdf viewers.  The link to my  original message is here:

https://stat.ethz.ch/pipermail/r-sig-mac/2005-March/001650.html

This problem still occurs and was wondering if there was any progress on
resolving it.  Thank you.

Here, again, is some code from the 2005 message that should permit
you to see the grid lines.

quartz()
chkb8 <- matrix(rep(c(rep(c(1,2), 4), rep(c(2,1), 4)), 4), ncol = 8)
chkb16 <- kronecker(chkb8, matrix(1, ncol=2, nrow=2))
chkb16[6:11, 6:11] <- 1
chkb16[8:9,8:9] <- 3
image(chkb16, axes=FALSE,col=c("red","green","yellow"))

Ken Knoblauch
	[[alternative text/enriched version deleted]]

