Shading region between vertical and diagonal lines in ggplot

I am trying to use ggplot to shade the region between the vertical line and the diagonal line as shown below. Is there a way to do this?

df <- data.frame(x=c(1,-1), y=c(1,-1))

ggplot(df, aes(x, y)) +
  geom_point() +
  geom_abline(slope=-1) +
  geom_vline(xintercept = 0)

>Solution :

It is a bit tricky, but if you know the coordinates of the area (Inf), you can use them to fill the shades using geom_polygon like this:

library(ggplot2)
df <- data.frame(x=c(1,-1), y=c(1,-1))
upper_area <- data.frame(x=c(-Inf,0,0),y=c(Inf,Inf,0))
down_area <- data.frame(x=c(0,0,Inf),y=c(0,-Inf,-Inf))

ggplot(df, aes(x, y)) +
  geom_point() +
  geom_abline(slope=-1) +
  geom_vline(xintercept = 0) +
  geom_polygon(aes(x=x, y=y), data=upper_area, fill="red") +
  geom_polygon(aes(x=x, y=y), data=down_area, fill="blue")

^{Created on 2022-07-15 by the reprex package (v2.0.1)}

old answer

It is a bit tricky, but if you know the coordinates of the area, you can use them to fill the shades using geom_polygon like this:

library(ggplot2)
df <- data.frame(x=c(1,-1), y=c(1,-1))
upper_area <- data.frame(x=c(-1,0,0),y=c(1,1,0))
down_area <- data.frame(x=c(0,0,1),y=c(0,-1,-1))

ggplot(df, aes(x, y)) +
  geom_point() +
  geom_abline(slope=-1) +
  geom_vline(xintercept = 0) +
  geom_polygon(aes(x=x, y=y), data=upper_area, fill="red") +
  geom_polygon(aes(x=x, y=y), data=down_area, fill="blue")

^{Created on 2022-07-15 by the reprex package (v2.0.1)}