[R] expression in lattice panel strip

[Naresh Gurbuxani]

Is it possible to include expression in lattice panel strip?
Thanks,
Naresh

cs <- 2 * cos(2 * pi * (1:500) / 50 + 0.6 * pi)
w <- rnorm(500)
xyplot(ts(cbind(x1 = cs, x2 = cs + w)), screens = list(x1 = expression(2 * cos(2 * pi * t / 50 + 0.6 * pi)), x2 = expression(2 * cos(2 * pi * t / 50 + 0.6 * pi) + N(0, 1))), type = c("l", "g"), main = expression(2 * cos(2 * pi * t / 50 + 0.6 * pi)))

# Greek letter pi is shown in main title, but not in panel strips