In the data set below, thing1 is numeric, and thing2 is a factor (but otherwise identical to thing1). For simplicity, the summary function is just the max value in the bin. When the z element is a factor, the hexagons overlap. Anyone know why?

```
library(ggplot2)
library(hexbin)
DF=data.frame(xpos=rnorm(1000), ypos=rnorm(1000), thing1=rep(1:9,length.out=100), thing2=as.factor(rep(1:9,length.out=100)))
ggplot(DF, aes(x=xpos, y=ypos, z=thing1)) + stat_summary_hex(fun=function(x){x[which.max(x)]})
ggplot(DF, aes(x=xpos, y=ypos, z=thing2)) + stat_summary_hex(fun=function(x){x[which.max(x)]})
```