How to reproduce smoothScatter's outlier plotting in ggplot?

Question

I am trying to get something like what the smoothScatter function does, only in ggplot. I have figured out everything except for plotting the N most sparse points.

Answer 1

Here is a workaround of sorts! Is doesn't work on the least dense n points, but plots all points with a density^0.25 less than x.

It actually plots the stat_density2d() layer, then the geom_point(, then the stat_density2d(), using alpha to create a transparent "hole" in the middle of the last layer where the density^0.25 is above (in this case) 0.4.

Obviously you have the performance hit of running three plots.

# Plot the ggplot version
ggplot(mydata) + aes(x=x, y=y) + scale_x_log10() + scale_y_log10() + 
  stat_density2d(geom="tile", aes(fill=..density..^0.25, alpha=1), contour=FALSE) + 
  geom_point(size=0.5) +
  stat_density2d(geom="tile", aes(fill=..density..^0.25,     alpha=ifelse(..density..^0.25<0.4,0,1)), contour=FALSE) + 
  scale_fill_gradientn(colours = colorRampPalette(c("white", blues9))(256))