Two Histograms in One Plot

applyfunction.R

## illustrate prior
prior <- rnorm(100000, 0.5, 0.5)

## extract posterior from Stan
posterior <- extract(my_stanfitobject)$my_parameter

## alternatively, create some second vector
vector2 <- rnorm(100000, 2, 0.8)

plot_two_histograms(prior, vector2, breaks = 100, 
                    upper_limit = 6, 
                    xlab = "vec1 is blue, vec2 is pink")