# Plot line over Histogram

#1

Hi,
I would like to draw a line on this histogram:

hist(rnorm(100, mean=15, sd=1), xlim=range(11:19), main="Size 100", xlab="x")

The line must show that this histogram is a Gaussian Curve!

I hope the question is understandable...

#2

That's a little tricky since the area under a Gaussian integrates to one, while a histogram plots frequencies/counts.

#3

As @EconomiCurtis points out, you have to change from a frequency histogram to a density histogram. It's all downhill from there:

``````data <- rnorm(100, mean=15, sd=1)
hist(data, xlim=range(11:19), main="Size 100", xlab="x", freq=FALSE)
``````

Obligatory Stack Overflow discussion: https://stackoverflow.com/q/1497539/37751

#4

You can also do it with `ggplot2` using `stat = density` and `stat_function()`:

``````library(dplyr)
library(ggplot2)

set.seed(100)

rnorm(100, mean=15, sd=1) %>%
as_tibble() %>%
ggplot(aes(value)) +
geom_histogram(stat = "density") +
stat_function(fun = function(x) {dnorm(x, 15, 1)}, color = "red") +
lims(x = c(11, 19))
``````

which gives you this: