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", "M"), each=200)),
  weight=round(c(rnorm(200, mean=55, sd=5),
                 rnorm(200, mean=65, sd=5)))
  )

(taken from: http://www.sthda.com/english/wiki/ggplot2-density-plot-quick-start-guide-r-software-and-data-visualization )

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

but when I change aes(y=..density..) to aes(y=..scaled..) I get an error.

If I use this example with my (big) data the density goes up to 120. So basically this: ![bar]http://www.sthda.com/sthda/RDoc/figure/easy-ggplot2/ggplot2-histogram-multiple-groups3.png with a different y-axis. (so that all bars of one type add up to 1)

I am not sure if it is statistically legit to use geom_smooth?

conrad-mac conrad-mac · Accepted Answer · 2017-01-27T23:23:03

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)

ggplot2 geom_density and geom_histrogram in one plot

1 Answers