[R] Combine two lattice plots including both plot keys

[Naresh Gurbuxani]

When I combine two lattice plots, only the first plot keys are
displayed.  Is it possible to show both keys?

Thanks,
Naresh

library(data.table)
library(lattice)
library(latticeExtra)

mydt <- data.table(year = rep(2020:2025, 2), bird = rep(c("duck",
"goose"), c(6, 6)))
mydt[, let(popstart = 100 + sample(-10:10, 12, replace = TRUE), popend =
120 + sample(-10:10, 12, replace = TRUE))]
mydt[, let(flights = rep(seq(200, by = 10, length.out = 6), 2) +
sample(-20:20, 12, replace = TRUE))]
mydt1 <- copy(mydt)[, let(obspot = "lake")]
mydt2 <- copy(mydt)[, let(obspot = "river")]
mydt <- rbindlist(list(mydt1, mydt2))
mydtmelt <- melt(mydt, id.vars = c("year", "bird", "obspot"),
measure.vars = c("popstart", "flights"))
popbar <- mydtmelt[, barchart(value ~ as.character(year) | bird +
obspot, groups = variable, horizontal = FALSE, stack = TRUE, auto.key =
list(columns = 2, space = "bottom")) |> useOuterStrips()]
popdot <-  mydt[, dotplot(popend ~ as.character(year) | bird + obspot,
type = "o", panel = function(x, y, ...){panel.dotplot(x, y, ...,
col.line = "transparent")}, key = simpleKey("popend", space = "top",
lines = TRUE, points = TRUE)) |> useOuterStrips()]

popbar # shows key at the bottom
popdot # shows key at the top

popbar + popdot # bottom key only