stat_function {ggplot2} | R Documentation

## Compute function for each x value

### Description

This stat makes it easy to superimpose a function on top of an existing plot. The function is called with a grid of evenly spaced values along the x axis, and the results are drawn (by default) with a line.

### Usage

    stat_function(mapping = NULL, data = NULL, geom = "path",
      position = "identity", ..., fun, xlim = NULL, n = 101, args = list(),
      na.rm = FALSE, show.legend = NA, inherit.aes = TRUE)

### 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.

`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.
`...` | other arguments passed on to `layer`. These are often aesthetics, used to set an aesthetic to a fixed value, like `color = "red"` or `size = 3`. They may also be parameters to the paired geom/stat.
`fun` | function to use. Must be vectorised.
`xlim` | Optionally, restrict the range of the function to this range.
`n` | number of points to interpolate along
`args` | list of additional arguments to pass to `fun`
`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.
`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`.

### Aesthetics

`stat_function` understands the following aesthetics (required aesthetics are in bold):

- `group`

- `y`

### Computed variables

x

  x's along a grid

y

  value of function evaluated at corresponding x

### Examples

    set.seed(1492)
    df <- data.frame(
      x = rnorm(100)
    )
    x <- df$x
    base <- ggplot(df, aes(x)) + geom_density()
    base + stat_function(fun = dnorm, colour = "red")
    base + stat_function(fun = dnorm, colour = "red", args = list(mean = 3))

    # Plot functions without data
    # Examples adapted from Kohske Takahashi

    # Specify range of x-axis
    ggplot(data.frame(x = c(0, 2)), aes(x)) +
      stat_function(fun = exp, geom = "line")

    # Plot a normal curve
    ggplot(data.frame(x = c(-5, 5)), aes(x)) + stat_function(fun = dnorm)

    # To specify a different mean or sd, use the args parameter to supply new values
    ggplot(data.frame(x = c(-5, 5)), aes(x)) +
      stat_function(fun = dnorm, args = list(mean = 2, sd = .5))

    # Two functions on the same plot
    f <- ggplot(data.frame(x = c(0, 10)), aes(x))
    f + stat_function(fun = sin, colour = "red") +
      stat_function(fun = cos, colour = "blue")

    # Using a custom function
    test <- function(x) {x ^ 2 + x + 20}
    f + stat_function(fun = test)

[Package ggplot2 version 2.2.1 Index]