geom_mark_hull: Annotate areas with hulls
In YTLogos/ggforce: Accelerating 'ggplot2'

Description Usage Arguments Aesthetics Author(s) Examples

This geom lets you annotate sets of points via hulls. While convex hulls are most common due to their clear definition, they can lead to large areas covered that does not contain points. Due to this geom_mark_hull uses concaveman which lets you adjust concavity of the resulting hull. The hull is calculated at draw time, and can thus change as you resize the plot. In order to clearly contain all points, and for aesthetic purpose the resulting hull is expanded 5mm and rounded on the corners. This can be adjusted with the expand and radius parameters.

geom_mark_hull(mapping = NULL, data = NULL, stat = "identity",
  position = "identity", expand = unit(5, "mm"), radius = unit(2.5, "mm"),
  concavity = 2, ..., na.rm = FALSE, show.legend = NA,
  inherit.aes = TRUE)

`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.
`stat`	The statistical transformation to use on the data for this layer, as a string.
`position`	Position adjustment, either as a string, or the result of a call to a position adjustment function.
`expand`	A numeric or unit vector of length one, specifying the expansion amount. Negative values will result in contraction instead. If the value is given as a numeric it will be understood as a proportion of the plot area width.
`radius`	As `expand` but specifying the corner radius.
`concavity`	A meassure of the concavity of the hull. `1` is very concave while it approaches convex as it grows. Defaults to `2`
`...`	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.
`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()`.

geom_mark_hull understand the following aesthetics (required aesthetics are in bold):

x
y
filter
color
fill
group
size
linetype
alpha

Thomas Lin Pedersen

ggplot(iris, aes(Petal.Length, Petal.Width)) +
  geom_mark_hull(aes(fill = Species, filter = Species != 'versicolor')) +
  geom_point()

# Adjusting the concavity lets you change the shape of the hull
ggplot(iris, aes(Petal.Length, Petal.Width)) +
  geom_mark_hull(aes(fill = Species, filter = Species != 'versicolor'),
                 concavity = 1) +
  geom_point()

ggplot(iris, aes(Petal.Length, Petal.Width)) +
  geom_mark_hull(aes(fill = Species, filter = Species != 'versicolor'),
                 concavity = 10) +
  geom_point()