[R] How to get a grid behind a boxplot

[Toby Popenfoose]

I am using R 2.2.1 on a Windows 2000 PC.  
When I do a grid() after the boxplot 
it overprints the boxplot:

> boxplot(count ~ spray, data = InsectSprays, col = "lightgray")
> grid(nx=NA, ny=NULL)
>

if I try the panel.first

> boxplot(count ~ spray, data = InsectSprays, col = "lightgray",
+         panel.first=grid(nx=NA, ny=NULL))
> 

I can see the grid flash and go away.  

If I close the device and then try the panel.first,
I do not get a boxplot and the following error message:

> boxplot(count ~ spray, data = InsectSprays, col = "lightgray",
+         panel.first=grid(nx=NA, ny=NULL))
Error in abline(h = at, col = col, lty = lty, lwd = lwd) : 
 plot.new has not been called yet
> 

Same thing when I try pdf device:

> pdf("test.pdf")
> boxplot(count ~ spray, data = InsectSprays, col = "lightgray",
+         panel.first=grid(nx=NA, ny=NULL))
Error in abline(h = at, col = col, lty = lty, lwd = lwd) : 
 plot.new has not been called yet
> dev.off()
null device 
          1 

How can I get the grid behind the boxplot?

Thank you,
Toby Popenfoose
Donnelley Manufacturing Supervisor
tpopenfoose at earthlink.net