R devel - Oct 2009 - Grid Graphics Documentation: color specification with gpar() (PR#14013)

Full_Name: Tom Gottfried
Version: 2.9.2
OS: Mac OS X 10.4.11
Submission from: (NULL) (93.104.160.207)


Dear R-Developers,

on the help page for gpar() is the following paragraph:

"Specifying the value NULL for a parameter is the same as not specifying
any
value for that parameter, except for col and fill, where NULL indicates not to
draw a border or not to fill an area (respectively)."

The mentioned exception for col and fill does not hold. Actually what is said in
the section "Color Specification" on the help page for par() is true
also for
gpar(): "transparent" and NA specify transparency respectively no
drawing.

To verify this:
grid.newpage()
grid.rect(width=.5, height=.5)
grid.rect(width=.25, height=.25, gp=gpar(col=NULL)) # draws the box despite
col=NULL
grid.rect(width=.125, height=.125, gp=gpar(col=NA, fill=2)) # does not draw the
box

regards,
Tom