How do I set the colour of my points on a scatterplot depending on the condition x < y?

Question

I have this scatterplot at the moment.

ggplot(pl, mapping = aes(x, y))+
  geom_point()+
  scale_x_continuous(limits = c(0,100))+
  scale_y_continuous(limits = c(0,100))+
  geom_abline(slope = 1, intercept = 1, color = "red")

which produces this

plot

I want to colour any points below the diagonal red and any above the diagonal green. So basically colour on the condition x < y. Thank you.

Does this answer your question? [Changing the shape of one point or few points in a scatter plot in R](https://stackoverflow.com/questions/67652479/changing-the-shape-of-one-point-or-few-points-in-a-scatter-plot-in-r) — user438383, Jul 05 '21 at 11:50

Basti · Accepted Answer · 2021-07-05T12:00:20.367

1

You can add the color argument in the ggplot() function with a condition x<y, and adding scale_color_identity() :

 ggplot(pl, mapping = aes(x, y,color=ifelse(x<y,"green","red")))+
  
  geom_point()+
  scale_x_continuous(limits = c(0,100))+
  scale_y_continuous(limits = c(0,100))+
  geom_abline(slope = 1, intercept = 1, color = "red")+
  
  scale_color_identity()

edited Jul 05 '21 at 12:00

answered Jul 05 '21 at 11:37

Basti

1,703
3
10
25

Perfect, thank you very much! – Sean Brennan Jul 05 '21 at 12:27

score 0 · Answer 2 · answered Jul 05 '21 at 11:37

You can add a column with the condition, and use that to color code your plot:

library(dplyr)
library(ggplot2)

ggplot(pl %>% mutate(threshold = case_when(
  x < y ~ TRUE,
  x >= y ~ FALSE),
mapping = aes(x, y, color = threshold))+
  geom_point()+
  scale_x_continuous(limits = c(0,100))+
  scale_y_continuous(limits = c(0,100))+
  geom_abline(slope = 1, intercept = 1, color = "red")

How do I set the colour of my points on a scatterplot depending on the condition x < y?

2 Answers2