Moving x or y axis together with tick labels to the middle of a single ggplot (no facets)

Question

I made the following plot in Excel:

But then I thought I would make it prettier by using ggplot. I got this far:

If you\'re curious, the da

Answer 1

just to complete baptiste's excellent answer with the equivalent for moving the y axis:

shift_axis_x <- function(p, x=0){
      g <- ggplotGrob(p)
      dummy <- data.frame(x=x)
      ax <- g[["grobs"]][g$layout$name == "axis-l"][[1]]
      p + annotation_custom(grid::grobTree(ax, vp = grid::viewport(x=1, width = sum(ax$height))), 
                            xmax=x, xmin=x) +
        geom_vline(aes(xintercept=x), data = dummy) +
        theme(axis.text.y = element_blank(), 
              axis.ticks.y=element_blank())
    }