Plot specific point data on each layer in stack with rasterVis in R

Question

I have 2 rasters stacked together:

library(rasterVis)
r1 <- raster(system.file("external/test.grd", package="raster")) 
r2 <- r1 / 2
r.stack <- stack(r1, r2)

Since I would like to highlight some areas later for each specific layer in the stack, I create two point datasets based on the raster values:

pts1 <- rasterToPoints(r1, spatial=T)
idx <- which(as.data.frame(pts1)[, 1] >= 400)
pts1 <- pts1[idx, 1]

pts2 <- rasterToPoints(r2, spatial=T)
idx <- which(as.data.frame(pts2)[, 1] >= 400)
pts2 <- pts2[idx, 1]

Now, I would like to plot the raster stack with levelplot from rasterVis in R. I would also like to overlay r1 with pts1 and r2 with pts2.

However, as soon as I add one point dataset, it is used for both layers:

levelplot(r.stack) + layer(sp.points(pts1, pch=20, cex=0.1, col="black"))

How can I use specific point datasets with specific layers while still using raster stacks?

I would like to avoid making my own subplot by plotting each layer with its' specific point dataset alone followed by using print.trellis. I tried it, but the result is just inferior compared to levelplot with raster stacks.

Any idea on how to achieve that?

Answer 1

With the panel.number function you can subset your data according to the panel you are located:

pts <- list(pts1, pts2)

levelplot(r.stack) +
    layer(sp.points(pts[[panel.number()]],
                    pch=20, cex=0.1, col="black"))