ggplot2 geom_density and geom_histrogram in one plot

Question

How can I make a histogram in which all bars add up to 1 and add a density layer above that fits?

set.seed(1234)
df <- data.frame(
  sex=factor(rep(c(\"F\", \         


        

Answer 1

Try using y = ..density../sum(..density..):

set.seed(1234)
df <- data.frame(
    sex=factor(rep(c("F", "M"), each=200)),
    weight=round(c(rnorm(200, mean=55, sd=5),
                   rnorm(200, mean=65, sd=5)))
)

library(ggplot2)

ggplot(df, aes(x=weight, color=sex, fill=sex)) + 
    geom_histogram(aes(y=..density../sum(..density..)), alpha=0.5, 
                   position="identity")+
    geom_density(alpha=.2)