geom_ridgeline {ggridges}

Plot a ridgeline (line with filled area underneath)

Description

Plots the sum of the y and height aesthetics versus x, filling the area between y and y + height with a color. Thus, the data mapped onto y and onto height must be in the same units. If you want relative scaling of the heights, you can use geom_density_ridges with stat = "identity".

Usage

geom_ridgeline(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  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.

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.

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.

...

other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like color = "red" or linewidth = 3. They may also be parameters to the paired geom/stat.

Details

In addition to drawing ridgelines, this geom can also draw points if they are provided as part of the dataset. The stat stat_density_ridges() takes advantage of this option to generate ridgeline plots with overlaid jittered points.

Aesthetics

Required aesthetics are in bold.

• x

• y

• height Height of the ridgeline, measured from the respective y value. Assumed to be positive, though this is not required.

• group Defines the grouping. Required when the dataset contains multiple distinct ridgelines. Will typically be the same variable as is mapped to y.

• scale A scaling factor to scale the height of the ridgelines. A value of 1 indicates that the heights are taken as is. This aesthetic can be used to convert height units into y units.

• min_height A height cutoff on the drawn ridgelines. All values that fall below this cutoff will be removed. The main purpose of this cutoff is to remove long tails right at the baseline level, but other uses are possible. The cutoff is applied before any height scaling is applied via the scale aesthetic. Default is 0, so negative values are removed.

• colour Color of the ridgeline

• fill Fill color of the area under the ridgeline

• alpha Transparency level of fill. Not applied to color. If you want transparent lines, you can set their color as RGBA value, e.g. #FF0000A0 for partially transparent red.

• group Grouping, to draw multiple ridgelines from one dataset

• linetype Linetype of the ridgeline

• linewidth Line thickness

• point_shape, point_colour, point_size, point_fill, point_alpha, point_stroke Aesthetics applied to points drawn in addition to ridgelines.

Examples

library(ggplot2)

d <- data.frame(x = rep(1:5, 3), y = c(rep(0, 5), rep(1, 5), rep(3, 5)),
                height = c(0, 1, 3, 4, 0, 1, 2, 3, 5, 4, 0, 5, 4, 4, 1))
ggplot(d, aes(x, y, height = height, group = y)) + geom_ridgeline(fill="lightblue")