R: Create quadratic or cubic bezier curves

geom_bezier {ggforce}

R Documentation

Create quadratic or cubic bezier curves

Description

This set of geoms makes it possible to connect points creating either quadratic or cubic beziers. bezier and bezier2 both work by calculating points along the bezier and connecting these to draw the curve. bezier0 directly draws the bezier using bezierGrob and is thus probably more performant. In line with the geom_link and geom_link2 differences geom_bezier creates the points, assign an index to each interpolated point and repeat the aesthetics for the start point, while geom_bezier2 interpolates the aesthetics between the start and end points.

Usage

stat_bezier(mapping = NULL, data = NULL, geom = "path",
  position = "identity", na.rm = FALSE, show.legend = NA, n = 100,
  inherit.aes = TRUE, ...)

geom_bezier(mapping = NULL, data = NULL, stat = "bezier",
  position = "identity", arrow = NULL, lineend = "butt", na.rm = FALSE,
  show.legend = NA, inherit.aes = TRUE, n = 100, ...)

stat_bezier2(mapping = NULL, data = NULL, geom = "path_interpolate",
  position = "identity", na.rm = FALSE, show.legend = NA, n = 100,
  inherit.aes = TRUE, ...)

geom_bezier2(mapping = NULL, data = NULL, stat = "bezier2",
  position = "identity", arrow = NULL, lineend = "butt", na.rm = FALSE,
  show.legend = NA, inherit.aes = TRUE, n = 100, ...)

stat_bezier0(mapping = NULL, data = NULL, geom = "bezier0",
  position = "identity", na.rm = FALSE, show.legend = NA,
  inherit.aes = TRUE, ...)

geom_bezier0(mapping = NULL, data = NULL, stat = "bezier0",
  position = "identity", arrow = NULL, lineend = "butt", 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), is combined with the default mapping at the top level of the plot. You only need to supply mapping if there isn't a mapping defined for the plot.
`data`	A data frame. If specified, overrides the default data frame defined at the top level of the plot.
`geom,`	stat Override the default connection between `geom_arc` and `stat_arc`.
`position`	Position adjustment, either as a string, or the result of a call to a position adjustment function.
`na.rm`	If `FALSE` (the default), removes missing values with a warning. If `TRUE` silently removes missing values.
`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.
`n`	The number of points to create for each segment
`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.
`...`	other arguments passed on to `layer`. There are three types of arguments you can use here: Aesthetics: to set an aesthetic to a fixed value, like `color = "red"` or `size = 3.` Other arguments to the layer, for example you override the default `stat` associated with the layer. Other arguments passed on to the stat.
`stat`	The statistical transformation to use on the data for this layer, as a string.
`arrow`	specification for arrow heads, as created by arrow()
`lineend`	Line end style (round, butt, square)

Details

Input data is understood as a sequence of data points the first being the start point, then followed by one or two control points and then the end point. More than 4 and less than 3 points per group will throw an error. bezierGrob only takes cubic beziers so if three points are supplied the middle one as duplicated. This, along with the fact that bezierGrob estimates the curve using an x-spline means that the curves produced by geom_bezier and geom_bezier2 deviates from those produced by geom_bezier0. If you want true bezier paths use geom_bezier or geom_bezier2.

Aesthetics

geom_link, geom_link2 and geom_lin0 understand the following aesthetics (required aesthetics are in bold):

x
y
color
size
linetype
alpha
lineend

Computed variables

x, y: The interpolated point coordinates
index: The progression along the interpolation mapped between 0 and 1

Author(s)

Thomas Lin Pedersen

Examples

beziers <- data.frame(
    x = c(1, 2, 3, 4, 4, 6, 6),
    y = c(0, 2, 0, 0, 2, 2, 0),
    type = rep(c('cubic', 'quadratic'), c(3, 4)),
    point = c('end', 'control', 'end', 'end', 'control', 'control', 'end')
)
help_lines <- data.frame(
    x = c(1, 3, 4, 6),
    xend = c(2, 2, 4, 6),
    y = 0,
    yend = 2
)
ggplot() + geom_segment(aes(x = x, xend = xend, y = y, yend = yend),
                        data = help_lines,
                        arrow = arrow(length = unit(c(0, 0, 0.5, 0.5), 'cm')),
                        colour = 'grey') +
    geom_bezier(aes(x= x, y = y, group = type, linetype = type),
                data = beziers) +
    geom_point(aes(x = x, y = y, colour = point), data = beziers)

[Package ggforce version 0.1.1 Index]