ggplot2 geom_smooth line not showing up on my graph

Question

I am trying to add a line through my plotted data using geom_smooth, but I am running into difficulty.

Here is my code:

plot.BG = ggplot(da         


        

Answer 1

Aesthetic mappings defined in ggplot() are inherited by subsequent layers. However, if mappings defined in a layer (e.g., inside geom_point()) are local to that layer only. Since you want the same mappings to be used by both the geom_point and the geom_smooth layers, put them in the initial ggplot() call and they will be inherited by both.

Reproducibly using mtcars:

# only the points are displayed
ggplot(mtcars) +
    geom_point(aes(x = hp, y = mpg, color = factor(cyl)) + 
    geom_smooth()

# you could respecify for the geom smooth, but that's repetitive
ggplot(mtcars) +
    geom_point(aes(x = hp, y = mpg, color = factor(cyl)) + 
    geom_smooth(aes(x = hp, y = mpg, color = factor(cyl))

# put the mapping up front for all layers to inherit it
ggplot(mtcars, aes(x = hp, y = mpg, color = factor(cyl)) +
    geom_point() + 
    geom_smooth()