[R] Combine two lattice plots including both plot keys

[Deepayan Sarkar]

On Sat, 5 Sept 2026 at 19:58, Naresh Gurbuxani <naresh_gurbuxani using hotmail.com>
wrote:

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

In principle yes, but clearly +.trellis doesn't try hard enough.

You could do

p = popbar + popdot
p$legend = c(popbar$legend, popdot$legend)
p

or more succintly

update(popbar + popdot, legend = c(popbar$legend, popdot$legend))

Best,
-Deepayan



>
> 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
>
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