ggplot2 move x-axis to top (intersect with reversed y axis at 0) [duplicate]

Question

I want to make a figure which have reversed y-axis and x-axis at y=0. y axis was reversed with scale_y_reverse, but x-axis stayed at the bottom.

p <- ggplot(df, aes(x= conc, y=depth, group=factor(stn), color=factor(stn)))+
geom_point(shape=1)+
geom_path(alpha=0.5)+
scale_y_reverse(limits=(c(20,0)), expand=c(0,0))+   
scale_x_continuous(expand=c(0,0))

I tried the code from this post like in below, but didn't work.

p + 
scale_x_continuous(guide = guide_axis(position = "top")) + 
scale_y_continuous(guide = guide_axis(position = "right"))

I don't need to have two x-axis, simply just move from bottom to the top.

Answer 1

This is still not possible in ggplot2, but it is possible in ggvis, which combines the ggplot2 grammer with dplyr pipelines. Just use the add_axis function to put the axis at the top.

# sample data
N <- 20
df <- data.frame(conc = seq(0, N), 
                 depth = runif(N+1, 0, 20), 
                 stn = rep(1:4, length=N+1))
# ggplot version
require(ggplot2)
p <- ggplot(df, aes(x= conc, y=depth, group=factor(stn), color=factor(stn)))+
  geom_point(shape=1)+
  geom_path(alpha=0.5)+
  scale_y_reverse(limits=(c(20,0)), expand=c(0,0))+   
  scale_x_continuous(expand=c(0,0))
p
# ggvis version
require(ggvis)
df %>% transform(stn = factor(stn)) %>%
  ggvis(x = ~conc, y = ~depth, stroke = ~stn) %>%
  layer_points(shape := "circle", fill := "white") %>%
  layer_lines(opacity := 0.5) %>%
  scale_numeric("y", reverse=TRUE, domain=c(0,20), expand=c(0,0)) %>%
  scale_numeric("x", expand=c(0,0)) %>%
  add_axis("x", orient = "top")