[R] Set panel background color in a multi-group trellis plot

[Bert Gunter]

Read ?panel.superpose carefully and pay attention to the comments about the
group.number argument passed to panel.groups. You can test the value of this
argument and adjust the plot accordingly.



Bert Gunter
Genentech Nonclinical Statistics
7-7374

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of crmontes at ncsu.edu
Sent: Friday, November 30, 2007 8:50 AM
To: r-help at r-project.org
Subject: [R] Set panel background color in a multi-group trellis plot

Hi everyone,

I am trying to change some of the default colors in a
multipanel-multigroup lattice graphic, but when I change the panel color
to white, the only group that is plotted is the last one, as panel.fill
overwrites all the previous ones.  Is there any way to set the panel
background color for the first panel to a color and keep the rest
transparent?

My code looks like this:

#first set defaults for getting more distinct symbols
superp.symbol <- trellis.par.get("superpose.symbol")
superp.symbol$pch = 15:21
superp.symbol$cex = 1.5
trellis.par.set("superpose.symbol", superp.symbol)

#set the default for the colors in the symbols
superp.lines <- trellis.par.get("superpose.line")
superp.lines$lty <- 1:6
superp.lines$lwd <- 1.5
trellis.par.set("superpose.line", superp.lines)

#set the device color to lightblue
trellis.par.set("background", list(col = "lightblue"))


xyplot(Volume ~ Age|Farm,
                groups       = Treatment,
                data         = my_data,
                panel        = panel.superpose,
                panel.groups =  function(x,y, ...)
                  {
                    panel.fill(col = "white")
                    panel.grid(col = "gray",lty = 2)
                    panel.xyplot(x,y,...)
                 }
                ,auto.key = list(location = "bottom"),
                main = "Main effects")


If I try to do something like

 if (panel.group == 1) panel.fill(col = "white")

I get an error saying panel.group doesn't exist.

Any thoughts?

Regards,

Cristián Montes
NC State University

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