Place ticks in middle of each colors in levelplot

Question

I am trying to place the ticks and names in middle of the each color in colorkeys but unable to do it. Is it possible to move the ticks in middle of color in levelplot?

> library (raster)
> ras <- list.files("/filepath/", pattern = "\\.tif$", full=TRUE)
> s <- stack(ras)
> levelplot(s, colorkey=list(at=seq(-3, 4, 1), labels=list(at=c(-3, -2, -1, 0, 1, 2,3, 4), labels=c("AA", "BB", "CC", "DD","EE", "FF", "GG")))

Answer 1

You can try something like this:

library (raster)
library(rasterVis)

ras <- lapply(1:3,function(i){
r <- raster()
values(r) <- sample(x = 1:10,size = ncell(r),replace = TRUE)
r
})
s <- stack(ras)
levelplot(s, colorkey=list(at=seq(-3, 4, 1), 
labels=list(at=c(-2.5, -1.5, -0.5,0.5, 1.5,2.5,3.5), 
labels=c("AA", "BB", "CC", "DD","EE", "FF", "GG"))))