How to plot x-axis labels and bars between tick marks in ggplot2 bar plot?

Question

I prepared a MWE and hope for help on how to set ticks and labels at different position on the x-axis for a grouped bar plot.

library(ggplot2)
library(reshap         


        

Answer 1

Here is another solution which uses grid package.

library(grid)

nTicks <- 2
tickersPosition <- unit(rep(1:nTicks /(nTicks+1), each=2), "native")

Part 1:nTicks /(nTicks+1) identifies positions where ticks will be placed.

p1 <- ggplot(data, aes(name,value)) +
  geom_bar(aes(fill = variable), position = "dodge", stat = "identity") 

To change position of ticks we need to create gtable

p2 <- ggplot_gtable(ggplot_build(p1))

and find the right grob (using str):

p2$grobs[[7]]$children$axis$grobs[[1]]$x <- tickersPosition

After the position is rewritten, we can run

grid::grid.draw(p2)

which will show warnings. This is because of a different number of splits.