Distribution of Predicted Probability with ggplot

library(ggplot2)
library(dplyr)

df = data.frame(
  y = factor(c(rep(0, 2000), rep(1, 500))),
  prob = c(rnorm(2000, 0.4, 0.1), rnorm(500, 0.6, 0.1))
  ) 

# Distribution of Predicted Probability with ggplot
ggplot(df, aes(x=prob, fill=y)) +
  geom_histogram(position="identity",alpha=0.3, binwidth=0.02)