ggplot stat_density2d无法绘制带有瓷砖几何图形的轮廓

Question

Using contours with stat_density2d gives error:

ggplot(faithful, aes(x = eruptions, y = waiting, fill = ..density..)) + 
  stat_density2d(geom = "tile")

Don't know how to automatically pick scale for object of type function. Defaulting to continuous. Error in is.finite(x) : default method not implemented for type 'closure'

Using contour = F plots without error. What is the issue?

Answer 1

In ggplot, geoms and stats must be paired in each layer added to the plot, so if you want both rasters/tiles and contour lines, you need to make two calls:

library(ggplot2)

ggplot(faithful, aes(x = eruptions, y = waiting)) + 
    stat_density2d(aes(fill = ..density..), geom = "raster", contour = FALSE) + 
    stat_density2d()

If you're aiming instead for filled contours, it's really hard without extending ggplot. Happily, that has already been done in the metR package:

ggplot(faithfuld, aes(eruptions, waiting, z = density)) + 
    metR::geom_contour_fill()

Note that I switched to faithfuld , which already has the density computed, as geom_contour_fill , like geom_contour , is designed to work with raster data. It may be possible to get geom_contour_fill to do the 2D density estimation for you, but it may be more straightforward to call MASS::kde2d (what stat_density2d uses) yourself and unpack the results to a data frame suitable for geom_contour_fill .