alaiacano

labels <- c(
  rep("a", 100*rexp(1)), 
  rep("b", 100*rexp(1)),
  rep("c", 100*rexp(1)),
  rep("d", 100*rexp(1)))
x <- data.frame(labels = factor(labels), some.value = runif(length(labels)))
qplot(labels, data=x)