Using scale_size_area (ggplot2) to plot points of size "0" as completely absent

Question

I'm trying to make a bubble plot of condition by cluster, where the size of each bubble is set by a third "percent" variable. As per the ggplot2 documentation, I think I should be able to do this via scale_size_area. I am unclear why this isn't working, and I still see very tiny points when percent=0. (If I am misunderstanding, I would also appreciate a solution on how to do this. In my real data, it is important to distinguish between 0 and very close to 0.)

ex <- data.frame(Condition=rep(c("ex1","ex2","ex3","ex4"),4),
                 Cluster=c(rep(1,4),rep(2,4),rep(3,4),rep(4,4)),
             Percent=c(0,0,0,1,0.25,0,0.25,0.5,1,0,0,0,0.25,0.25,0.25,0.25))
ggplot(ex, aes(Cluster, Condition, size=Percent))+ 
           geom_point(color = "blue")+ scale_size_area(max_size=20)

Answer 1

Try

library(ggplot2)
ex <- data.frame(Condition=rep(c("ex1","ex2","ex3","ex4"),4),
                 Cluster=c(rep(1,4),rep(2,4),rep(3,4),rep(4,4)),
             Percent=c(0,0,0,1,0.25,0,0.25,0.5,1,0,0,0,0.25,0.25,0.25,0.25))
ggplot(ex, aes(Cluster, Condition, size=ifelse(Percent==0, NA, Percent))))+ 
           geom_point(color = "blue")+ scale_size_area(max_size=20)

Using size=ifelse(Percent==0, NA, Percent)) instead of size=Percent will exclude those points from drawing.