A ggplot2 layer that fits and plots normal density function

A ggplot2 layer that fits and plots a theoretical normal density function. May be used to visually compare between empirical and theoretical normal distributions.

stat_normal_density(
  mapping = NULL,
  data = NULL,
  geom = "line",
  position = "identity",
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  trim = 0,
  ...
)

Arguments

mapping	Set of aesthetic mappings created by aes() or aes_(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.
data	The data to be displayed in this layer. There are three options: If NULL, the default, the data is inherited from the plot data as specified in the call to ggplot(). A data.frame, or other object, will override the plot data. All objects will be fortified to produce a data frame. See fortify() for which variables will be created. A function will be called with a single argument, the plot data. The return value must be a data.frame, and will be used as the layer data. A function can be created from a formula (e.g. ~ head(.x, 10)).
geom	The geometric object to use display the data
position	Position adjustment, either as a string, or the result of a call to a position adjustment function.
na.rm	If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.
show.legend	logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.
inherit.aes	If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().
trim	(numeric) Fraction of points to trim before computing mean and standard deviation, which are used to construct theoretical normal distribution. Number between 0 and 1. Default is 0.
...	Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

Computed variables

density

normal density

ndensity

normal density scaled to maximum of 1

count

normal density * number of points

Examples

library(ggplot2)
library(biostat)

ggplot(mtcars, aes(mpg)) +
  stat_normal_density()

ggplot(mtcars, aes(mpg)) +
  stat_density(alpha = 0.8) +
  stat_normal_density(color = "red", size = 1)