Assigndifferent paletes to different geoms but same scale

Question

For example

library(ggplot2)
ggplot(iris, aes(Sepal.Length, Sepal.Width))+
  geom_point(aes(color = Species)) +
  geom_smooth(aes(color = Species, fill = Species), method = "lm", se = FALSE)

Is there some way to assign a palette (for example through scale_color_discrete) to points and a different paler to the lines produced by geom_smooth?

Thank you!

Answer 1

There isn't a very clean way to do this within ggplot2, but there is a package called ggnewscale that will help.

library(ggplot2)
library(ggnewscale)

ggplot(iris, aes(Sepal.Length, Sepal.Width))+
  geom_point(aes(color = Species)) +
  scale_colour_brewer(palette = 1) +
  ggnewscale::new_scale_color() +
  geom_smooth(aes(color = Species), method = "lm", se = FALSE) +
  scale_colour_brewer(palette = 2)
#> `geom_smooth()` using formula = 'y ~ x'

^{Created on 2024-07-06 with reprex v2.1.1}

Another solution without any new packages, is just changing the color to fill and giving the points a shape.

library(ggplot2)
library(ggnewscale)

ggplot(iris, aes(Sepal.Length, Sepal.Width))+
  geom_smooth(aes(color = Species), method = "lm", se = FALSE) +
  geom_point(aes(fill = Species), shape = 21, size = 3, colour="transparent") +
  scale_colour_brewer(palette = 2) +
  scale_fill_brewer(palette = 1) 
#> `geom_smooth()` using formula = 'y ~ x'

^{Created on 2024-07-06 with reprex v2.1.1}