ggplot and axis numbers and labels

Question

i tried to build the following sample plot (see here for an example of a CIELAB Color Wheel). It is nearly finished, but there are still some small issues (see demo): - the

Answer 1

moving the whole axis inside the plot panel is not straight-forward (arguably for good reasons). You can do it like this,

g <- ggplotGrob(p)

library(gtable)
# move the axis up in the gtable
g$layout[g$layout$name == "axis-b", c("t", "b")] <- 
  g$layout[g$layout$name == "panel", c("t", "b")] 
# extract the axis gTree and modify its viewport 
a <- g$grobs[[which(g$layout$name == "axis-b")]] 
a$vp <- modifyList(a$vp, list(y=unit(0.5, "npc")))
g$grobs[[which(g$layout$name == "axis-b")]] <- a


g$layout[g$layout$name == "axis-l", c("l", "r")] <- 
  g$layout[g$layout$name == "panel", c("l", "r")] 
# extract the axis gTree and modify its viewport 
b <- g$grobs[[which(g$layout$name == "axis-l")]] 
b$vp <- modifyList(b$vp, list(x=unit(0.5, "npc")))
g$grobs[[which(g$layout$name == "axis-l")]] <- b

#grid.newpage()
#grid.draw(g)


## remove all cells but panel
panel <- g$layout[g$layout$name == "panel",] 

gtrim <- g[panel$b, panel$r]
## add new stuff
gtrim <- gtable_add_rows(gtrim, unit(1,"line"), pos=0)
gtrim <- gtable_add_rows(gtrim, unit(1,"line"), pos=-1)
gtrim <- gtable_add_cols(gtrim, unit(1,"line"), pos=0)
gtrim <- gtable_add_cols(gtrim, unit(1,"line"), pos=-1)

gtrim <- gtable_add_grob(gtrim, list(textGrob("top"),
                                     textGrob("left", rot=90),
                                     textGrob("right", rot=90),
                                     textGrob("bottom")), 
                         t=c(1,2,2,3),
                         l=c(2,1,3,2))

grid.newpage()
grid.draw(gtrim)