filups21 filups21 - 10 months ago 130
R Question

multiple kernal densities in ggplot2

I would like to add a kernel density estimate for 2 types of data to a ggplot. If I use the following code, it displays a kernel density estimate for the 2nd factor level only. How do I get a kernel density estimate for both factor levels (preferably different colors)?

ggplot(mtcars, aes(x = disp, y=mpg, color=factor(vs))) +
theme_bw() +
geom_point(size=.5) +
geom_smooth(method = 'loess', se = FALSE) +
stat_density_2d(geom = "raster", aes(fill = ..density.., alpha = ..density..), contour = FALSE) +
scale_alpha(range = c(0,1)) +
guides(alpha=FALSE)


enter image description here

Answer Source

One approach is to use two stat_density_2d layers with subsets of the data and manually color them. It is not exactly what you are after but with tweaking it can be solid:

ggplot(mtcars, aes(x = disp, y=mpg, color=factor(vs))) +
  theme_bw() +
  geom_point(size=.5) +
  geom_smooth(method = 'loess', se = FALSE) +
  stat_density_2d(data = subset(mtcars, vs == 0), geom = "raster", aes(alpha = ..density..), fill = "#F8766D" , contour = FALSE) +
  stat_density_2d(data = subset(mtcars, vs == 1), geom = "raster", aes(alpha = ..density..), fill = "#00BFC4" , contour = FALSE) +
  scale_alpha(range = c(0, 1)) 

enter image description here

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