plotting pie graphs on map in ggplot

Question

This may be a wish list thing, not sure (i.e. maybe there would need to be the creation of geom_pie for this to occur). I saw a map today (LINK) with pie graph

Answer 1

This functionality should be in ggplot, I think it is coming to ggplot soonish, but it is currently available in base plots. I thought I would post this just for comparison's sake.

load(url("http://dl.dropbox.com/u/61803503/nycounty.RData"))

library(plotrix)
e=10^-5
myglyff=function(gi) {
floating.pie(mean(gi$long),
             mean(gi$lat),
             x=c(gi[1,"white"]+e,
                 gi[1,"black"]+e,
                 gi[1,"hispanic"]+e,
                 gi[1,"asian"]+e,
                 gi[1,"other"]+e),
              radius=.1) #insert size variable here
}

g1=ny[which(ny$group==1),]
plot(g1$long,
     g1$lat,
     type='l',
     xlim=c(-80,-71.5),
     ylim=c(40.5,45.1))

myglyff(g1)

for(i in 2:62)
  {gi=ny[which(ny$group==i),]
    lines(gi$long,gi$lat)
    myglyff(gi)
  }

Also, there may be (probably are) more elegant ways of doing this in the base graphics.

As, you can see, there are quite a few problems with this that need to be solved. A fill color for the counties. The pie charts tend to be too small or overlap. The lat and long do not take a projection so sizes of counties are distorted.

In any event, I am interested in what others can come up with.