Why does geom_vline not inherit the colour scale palette?

[davidhodge931]

Hi All,

In the below example, why does the vline not get coloured blue? I would have thought the colour scale would be inherited by all layers with the col aesthetic.

I understand that I could add a col = "blue" argument to geom_vline, but I am trying to get my head around how colour scales work.

library(tidyverse)
library(palmerpenguins)

penguins %>% 
  ggplot(aes(flipper_length_mm, body_mass_g, colour = "1")) +
  geom_point() +
  geom_vline(xintercept = 200) +
  scale_color_manual(values = "blue") 

Thanks
David

[nirgrahamuk]

I think the answer is that geom_vline does not consider any aesthetics, it just draws a line given the intercept.

[M_AcostaCH]

Maybe you need specify the exactly color and other options, like colour, linetype and size.

library(tidyverse)
library(palmerpenguins)

penguins %>% 
  ggplot(aes(flipper_length_mm, body_mass_g, colour = "1")) +
  geom_point() +
  geom_vline(xintercept = 200, colour="#62CC10", linetype="dashed", size= 1.5) +
  scale_color_manual(values = "blue") 

[andresrcs]

@davidhodge931

geom_vline(xintercept = 200) +

When you provide the xintercept argument, outside of an aes() mapping, geom_vline() behaves like an annotation, not like a mapped geom, so, it ignores any mapping definition. You would need to pass the colour property as an argument, as you would do with an annotation.