graphics - R histogram with multiple populations

Question

I'm interested in creating a histogram in R that will contain two (or more) population on top of each other, meaning - I don't want a two histograms sharing the same graph but a bar containing two colors or more.

Found the image below - this is what I want to accomplish.

Any ideas?

Answer 1

That is actually the annoying default in ggplot2:

library(ggplot2)
ggplot(iris, aes(x=Sepal.Length, fill=Species)) +
  geom_histogram()