ggplot2: piecharts instead of points in an xy scatterplot

Question

I have a four-dimensional dataset, let\'s call the variables x, y, z and r. There is at most one entry for each combination of x and y. Currently, I have a scatterplot where

Answer 1

This does the trick:

ggplot(aes(x=x,y=y)) + geom_point(aes(size=z)) + stat_spoke(aes(angle=r*2*pi, radius=3*z))