[R] Help with lattice panel function

[Naresh Gurbuxani]

I want to plot multiple variables in xyplot, but plot loess trend for only one of these variables.  My problem is that the last command below does not give the desired result. 
Any help will be gratefully received.
Thanks,Naresh
my.df <- data.frame(date = as.numeric(as.Date("2015-01-01")) + 0:49, x = rnorm(50))
my.df$date <- as.Date(my.df$date, origin = as.Date("1970-01-01"))


library(zoo)
x <- zoo(my.df[,"x"], my.df[,"date"])
max.x <- rollapply(x, 10, max, align = "right")
x <- merge(x, max.x)
my.newdf <- data.frame(x)
my.newdf$date <- as.Date(row.names(my.newdf))


library(lattice)# This works as expected
xyplot(x + max.x ~ date, data = my.newdf, type = "l", 
   auto.key = list(columns = 2, points = FALSE, lines = TRUE), ylab = "x")
   # This does not work
xyplot(x ~ date, data = my.newdf, y2 = max.x, ylab = "x",
   panel = function(x, y, x2, ...){
   	panel.xyplot(x, y, type = "l")
   	panel.loess(x, y, lty = 2)
   	panel.xyplot(x, y2, type = "l")
   })      		 	   		  
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