lattice: plotting in a loop

Hi,

I'm having trouble seeing graphics output from lattice xyplot() when called
from inside a for loop:

x <- 1:50
for ( i in 1:5 ) {
?y <- rnorm(x)
?xyplot(y~x) ? ? ? ? ?# no graphics when inside for-loop
# plot(x,y) ? ? ? ? ? ?# works fine
# Sys.sleep(0.5) ? ? ? # doesn't seem to help
}

The xyplot() is fine outside the loop. ?Results are the same to X11 device
and to file devices.

I have noticed that there is a delay proportional to the size of the loop,
so presumably xyplot() is computing although the results aren't reaching the
graphics device.

Can anyone suggest a cause or remedy?

This is my first post to the list, although I've picked up a lot of useful
information reading here!

-Ryan

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