Ah, wonderful, thank you for the code Deepayan. To recap for posterity: I
have two datafiles, d and q: each has x-y coordinates that are conditioned
by site (The actual data, for me, is maps of parent trees and their
seedlings). I wanted to superimpose the xy plots of d and q, by site,
without going to the trouble of merging the d & q datasets into a single
dataset. The solution is to use the "which.packet" statement is
d <- data.frame(site = c(rep("A",12), rep("B",12)),
x=rnorm(24),y=rnorm(24)) # Create the main xy dataset
q <- data.frame(site = c(rep("A",7), rep("B",7)),
x=rnorm(14),y=rnorm(14)) # Create the alternate xy dataset
q.split <- split(q, q$site) # Split up the alternate
dataset by site
mypanel <- function(..., alt.data) {
with(alt.data[[ which.packet()[1] ]], #
which.packet passes index of the relevant data subset...
panel.xyplot(x = x, y = y, col="red")) # ... to
panel.xyplot()
panel.xyplot(...)
}
xyplot(y ~ x | site, d, alt.data = q.split, # After providing
the alternative dataset and the panel...
panel = mypanel) # ...everything prints out
properly, like magic!
Dr. Seth W. Bigelow
Biologist, USDA-FS Pacific Southwest Research Station
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